Biomedical subjects

Craig W Stevens

Publications and source records attributed to Craig W Stevens.

At least 19 recordsLinked to original sources

PubMed2004

Evaluation of internal lung motion for respiratory-gated radiotherapy using MRI: Part II-margin reduction of internal target volume.

PURPOSE: To analyze the relationship between lung motion and skin surface motion during respiration, determine the uncertainties and variability of such a relationship, and assess the potential of reducing internal target margin for gated radiotherapy. METHODS AND MATERIALS: Three healthy volunteers and four lung cancer patients were recruited in a prospective imaging study using MRI to track the internal lung and external skin motion during breathing. The relationship between the lung and skin motion was modeled using linear regression analysis. The slope of the linear fit and its confidence interval were analyzed for different lung locations, skin surface locations, and breathing patterns from separate imaging sessions. The margins of the internal target volume were calculated based on the residual lung motion during gating and its uncertainties from multiple treatment fractions for the gated treatment. RESULTS: The slope and confidence interval of the linear regression from the motion analysis were uniquely defined by the locations of the lung, skin surface, and breathing patterns. Statistically significant differences were observed among individuals and between different times of measurement. The normal free-breathing motion averaged from all volunteer and patient data was 13.4 +/- 7.4 mm along the superior-inferior (SI) direction and 6.9 +/- 2.6 mm along the anterior-posterior (AP) direction. With simulated respiratory gating, the average margin reduction was 5.5 +/- 4.8 mm and 1.6 +/- 1.0 mm, respectively, along the SI and AP directions (or 36% +/- 15% and 25% +/- 14%, respectively, relative to free-breathing motion). CONCLUSION: Because respiratory movement is rather complex, the relationship between the lung and skin surface motion is affected by many anatomic and physiologic factors. The reduction of internal target margin and efficacy of the free-breathing gating technique should be assessed for individual cases.

Adult↗

PubMed2004

Evaluation of internal lung motion for respiratory-gated radiotherapy using MRI: Part I--correlating internal lung motion with skin fiducial motion.

PURPOSE: To measure the internal lung motion due to respiration using magnetic resonance images (MRIs); to evaluate the correlation between lung motion and skin surface motion and the reliability of tracking lung motion with external fiducials. METHODS AND MATERIALS: An MRI protocol using fast gradient-echo sequences was developed to acquire dynamic cine images of the thoracoabdominal region along the axial, sagittal, and coronal planes. The subjects (3 healthy volunteers and 4 lung cancer patients) were instructed to perform normal or altered breathing during MRI. Lung vessels identified on MRI were used as anatomic landmarks for internal lung structures. From sagittal cine MRI scans, the positions of the lung vessels and skin surface were tracked and their movements measured. Correlation between the movements of the external markers and internal structures was then calculated and analyzed. RESULTS: Lung vessel motion in the superior-inferior (SI) direction correlated best with mid-upper abdominal skin surface movement (correlation coefficient, 0.89 +/- 0.09 and 0.87 +/- 0.23 for volunteers and patients, respectively). The anterior-posterior (AP) vessel motion generally correlated poorly with the skin surface movement, with marker placement on the upper chest yielding the strongest results (correlation coefficient, 0.72 +/- 0.23 and 0.44 +/- 0.27 for volunteers and patients, respectively). The strength of the correlation depended on the locations of the tracked vessels, locations of the skin surface, and subjects' breathing patterns. The best correlation was seen between the motion of an abdominal fiducial and SI lung motion. Significant intersubject variability was also observed. CONCLUSION: Movement of an external fiducial may not correlate fully with, or predict, internal lung motion. Effective monitoring of respiration may have to rely on a combination of multiple fiducials and other physiologic parameters, such as lung volume and/or air flow.

Adult↗

PubMed2004

Esophagectomy after concurrent chemoradiotherapy improves locoregional control in clinical stage II or III esophageal cancer patients.

PURPOSE: To evaluate the effect of surgical resection on the outcome of patients with clinical Stage II or III cancer of the esophagus treated with concurrent chemoradiotherapy. METHODS AND MATERIALS: A retrospective review of 132 consecutive patients with clinical Stage II or III esophageal cancer treated with concurrent chemoradiotherapy between January 1990 and December 1998 was performed. Of the 132 patients, 60 underwent esophagectomy 6-8 weeks after chemoradiotherapy. The median radiation dose was 50 Gy (range, 30-64.8 Gy) in the definitive chemoradiation group and 45 Gy (range, 30-50.4 Gy) in the chemoradiation plus esophagectomy group. RESULTS: Statistically significant differences were found between the two groups in median age, histologic subtype, tumor location, and number of patients with T4 disease. Patients who underwent definitive chemoradiotherapy were older (p = 0.0004) and more likely to have squamous cell carcinoma than adenocarcinoma (p <0.000), upper thoracic or cervical esophageal tumors (p <0.000), and T4 tumors (p = 0.024). Patients treated with chemoradiation plus esophagectomy had statistically significant superior 5-year loco-regional control (67.1% vs. 22.1%, p <0.000), disease-free survival (40.7% vs. 9.9%, p < 0.000), and 5-year overall survival (52.6% vs. 6.5%, p < 0.000) rates and median survival time (62 vs. 12 months) compared with patients treated with chemoradiotherapy only. However, no statistically significant difference was found in the rate of distant metastasis-free survival between the two groups (67.5% vs. 65.8%, p = 0.3). Surgical resection of the tumor was an independent predictor of improved locoregional control and overall survival in both univariate and multivariate analyses. To reduce the effect of the selection bias on the outcome, 34 patients in each group with matched pretreatment characteristics were compared. The results showed statistically significant better overall survival, disease-free survival, and locoregional control in favor of the chemoradiotherapy plus esophagectomy group. No statistically significant difference in distant metastasis-free survival was found in this subgroup analysis. CONCLUSIONS: Locoregional control was better in clinical Stage II or III esophageal cancer patients treated with concurrent chemoradiation plus esophagectomy. An improvement in survival occurred in the chemoradiation plus esophagectomy group, although this observation may have reflected selection bias. The results from this study suggest the need for a randomized trial to compare chemoradiation with or without esophagectomy in the treatment of cancer of the esophagus.

Adenocarcinoma↗

PubMed2004

Correlation of gross tumor volume excursion with potential benefits of respiratory gating.

PURPOSE: To test the hypothesis that the magnitude of thoracic tumor motion can be used to determine the desirability of respiratory gating. METHODS AND MATERIALS: Twenty patients to be treated for lung tumors had computed tomography image data sets acquired under assisted breath hold at normal inspiration (100% tidal volume), at full expiration (0% tidal volume), and under free breathing. A radiation oncologist outlined gross tumor volumes (GTVs) on the breath-hold computed tomographic images. These data sets were registered to the free-breathing image data set. Two sets of treatment plans were generated: one based on an internal target volume explicitly formed from assessment of the excursion of the clinical target volume (CTV) through the respiratory cycle, representing an ungated treatment, and the other based on the 0% tidal volume CTV, representing a gated treatment with little margin for residual motion. Dose-volume statistics were correlated to the magnitude of the motion of the center of the GTV during respiration. RESULTS: Patients whose GTVs were >100 cm(3) showed little decrease in lung dose under gating. The other patients showed a correlation between the excursion of the center of the GTV and a reduction in potential lung toxicity. As residual motion increased, the benefits of respiratory gating increased. CONCLUSION: Gating seems to be advantageous for patients whose GTVs are <100 cm(3) and for whom the center of the GTV exhibits significant motion, provided residual motion under gating is kept small.

Humans↗

PubMed2004

Induction chemotherapy improved outcomes of patients with resectable esophageal cancer who received chemoradiotherapy followed by surgery.

PURPOSE: To investigate the effect of induction chemotherapy (CHT) before trimodality therapy on the outcome of patients with resectable cancer of the esophagus. METHODS AND MATERIALS: This retrospective study included 81 consecutive patients with resectable cancer of the esophagus who received neoadjuvant chemoradiotherapy followed by esophagectomy between January 1990 and December 1998 (inclusive). Thirty-nine patients underwent chemoradiotherapy followed by esophagectomy (CHT/RT+S), 42 received additional induction CHT followed by CHT/RT+S (CHT+CHT/RT+S). Of the 81 patients, 47 were entered in institutional or national prospective trials (6 in the CHT/RT+S and 41 in the CHT+CHT/RT+S group). Induction CHT consisted of three courses of 5-fluorouracil (5-FU), cisplatin, and paclitaxel given in 28-day cycles in 37 patients (88.1%). Concurrent CHT was 5-FU and platinum based. The median radiation dose for patients treated with CHT/RT+S was 30 Gy (range, 30-50.4 Gy) delivered in a median of 10 fractions (range, 10-28 fractions) and 45 Gy (range, 30-45 Gy) in a median of 25 fractions (range, 10-25 fractions) for patients treated with CHT+CHT/RT+S. Esophagectomy was performed 6-8 weeks after completion of concurrent chemoradiotherapy. Most patients underwent transthoracic esophagectomy (n = 66, 82.5%). RESULTS: The pretreatment characteristics were well balanced between the two groups except for age. The median follow-up time was 29 months (22 months for the CHT/RT+S group and 38.5 months for the CHT+CHT/RT+S group) for all patients and 49 months for living patients. The actuarial overall survival (OS), disease-free survival (DFS), locoregional control (LRC), and distant metastasis-free survival (DMFS) rate at 5 years for the entire group was 46%, 36.6%, 70.7%, and 53.2%, respectively. Statistically significant differences in the OS, DFS, and LRC rates between the two groups were detected. Specifically, the 5-year OS rate was 22.8% and 71.1% in the CHT/RT+S and CHT+CHT/RT+S group (p = 0.0001), respectively. The 5-year DFS rate was 27.6% and 56.6% in the CHT/RT+S and CHT+CHT/RT+S group (p = 0.003), respectively. The 5-year LRC rate was 64.2% and 85.6% in the CHT/RT+S and CHT+CHT/RT+S group (p = 0.007), respectively. The difference in the DMFS rate between the two groups was statistically significant, with a 2- and 5-year actuarial rate of 63.9% and 51.9%, respectively, in the CHT/RT+S group and 76.9% and 74.1%, respectively, in the CHT+CHT/RT+S group (p = 0.04). The statistically significant differences persisted when patients who received >/=45 Gy in each group were compared. Among those patients, the 5-year OS, DFS, LRC, and DMFS rates were 23.1%, 15.4%, 58.6%, and 39.2%, respectively, for those receiving CHT/RT+S, and 71.4% (p = 0.001), 55.8% (p = 0.0008), 84.6% (p = 0.005), and 77.3% (p = 0.009), respectively, for those receiving CHT+CHT/RT+S. The pathologic complete response (pCR) rate was greater in the CHT+CHT/RT+S group compared with in the CHT/RT+S group (p = 0.008). In univariate analysis, young age, good Karnofsky performance status, Stage II disease, total radiation dose, multiple drug regimen for concurrent CHT, pCR, R0 resection, distant disease progression, and CHT+CHT/RT+S treatment proved to be prognostic factors for OS. Lower esophageal/gastroesophageal junction tumor location, pCR, R0 resection, and CHT+CHT/RT+S treatment were favorable prognostic factors for LRC. Neither the total radiation dose nor multiple drugs for concurrent CHT were negative prognostic factors for LRC. In multivariate analysis, pCR, R0 resection, and treatment with CHT+CHT/RT+S were independent positive predictive factors for OS, and distant recurrences were negative predictive factors for OS. R0 resection, CHT+CHT/RT+S treatment, and lower esophageal/gastroesophageal junction tumor location were positive predictive factors for LRC. The radiation dose was not identified as an independent prognostic factor for either OS or LRC in the multivariate analysis. Meaningful multivariate analysis could not be performed when the multiple drug vperformed when the multiple drug variable was included in the model because of the small number of patients. CONCLUSION: Significantly greater LRC, DFS, OS, and DMFS were found in patients treated with CHT+CHT/RT+S compared with those treated with CHT/RT+S. The pCR rate was significantly higher in the CHT+CHT/RT+S group. Induction CHT was an independent favorable prognostic factor for both LRC and OS for the population included in this study. Our data suggest that a randomized trial comparing CHT+CHT/RT+S and CHT/RT+S is warranted to assess further the merits of this treatment in patients with this currently very lethal cancer.

Adult↗

PubMed2004

Accumulation of the common mitochondrial DNA deletion induced by ionizing radiation.

Point mutations and deletions in mitochondrial DNA (mtDNA) accumulate as a result of oxidative stress, including ionizing radiation. As a result, dysfunctional mitochondria suffer from a decline in oxidative phosphorylation and increased release of superoxides and other reactive oxygen species (ROS). Through this mechanism, mitochondria have been implicated in a host of degenerative diseases. Associated with this type of damage, and serving as a marker of total mtDNA mutations and deletions, the accumulation of a specific 4977-bp deletion, known as the common deletion (Delta-mtDNA(4977)), takes place. The Delta-mtDNA(4977) has been reported to increase with age and during the progression of mitochondrial degeneration. The purpose of this study was to investigate whether ionizing radiation induces the formation of the common deletion in a variety of human cell lines and to determine if it is associated with cellular radiosensitivity. Cell lines used included eight normal human skin fibroblast lines, a radiosensitive non-transformed and an SV40 transformed ataxia telangiectasia (AT) homozygous fibroblast line, a Kearns Sayre Syndrome (KSS) line known to contain mitochondrial deletions, and five human tumor lines. The Delta-mtDNA(4977) was assessed by polymerase chain reaction (PCR). Significant levels of Delta-mtDNA(4977) accumulated 72 h after irradiation doses of 2, 5, 10 or 20 Gy in all of the normal lines with lower response in tumor cell lines, but the absolute amounts of the induced deletion were variable. There was no consistent dose-response relationship. SV40 transformed and non-transformed AT cell lines both showed significant induction of the deletion. However, the five tumor cell lines showed only a modest induction of the deletion, including the one line that was deficient in DNA damage repair. No relationship was found between sensitivity to radiation-induced deletions and sensitivity to cell killing by radiation.

Adolescent↗

PubMed2004

Effects of amifostine on acute toxicity from concurrent chemotherapy and radiotherapy for inoperable non-small-cell lung cancer: report of a randomized comparative trial.

PURPOSE: To determine the ability of amifostine to reduce the severity and/or incidence of the acute toxicities of concurrent chemotherapy and radiotherapy (RT) for non-small-cell lung cancer. METHODS AND MATERIALS: Patients with inoperable, nonmetastatic non-small-cell lung cancer receiving concurrent chemoradiotherapy were randomized to one of two treatment groups. Arm 1 patients received thoracic RT (total dose, 69.6 Gy in 58 fractions of 1.2 Gy b.i.d. 5 d/wk), plus oral etoposide (50 mg b.i.d. 30 min before thoracic RT for 10 days, repeated on Day 29) and cisplatin (50 mg/m2 i.v. on Days 1, 8, 29, and 36). Arm 2 patients received the same treatment plus amifostine (500 mg i.v. 20-30 min before any treatment the first 2 days of each week). Acute effects were assessed using the National Cancer Institute Common Toxicity Criteria. RESULTS: Sixty-two patients were enrolled between November 1998 and January 2001. The minimal follow-up was 24 months, and the median follow-up of living patients was 31 months. The patient and tumor characteristics were equally distributed between the patients in the two arms. The median survival time was 20 months in Arm 1 patients and 19 months in Arm 2 patients. The maximal esophageal toxicity was mild (Grade 1) in 23%, moderate (Grade 2) in 42%, and severe (Grade 3-4) in 35% of patients in Arm 1; the corresponding rates for the Arm 2 patients were 48%, 35%, and 16% (p = 0.021). Severe pneumonitis occurred in 16% of the Arm 1 and none of the Arm 2 patients (p = 0.020, chi-square test). Neutropenic fever occurred in 39% of Arm 1 and 16% of Arm 2 patients (p = 0.046, chi-square test). Mild hypotension, dysgeusia, and sneezing were significantly more frequent among the patients in Arm 2. CONCLUSION: Amifostine reduced the severity and incidence of acute esophageal, pulmonary, and hematologic toxicity resulting from concurrent cisplatin-based chemotherapy and RT. Amifostine had no apparent effect on survival in these patients with unresectable non-small-cell lung cancer, suggesting that it does not have a tumor-protective effect.

Adult↗

PubMed2004

Feasibility of sparing lung and other thoracic structures with intensity-modulated radiotherapy for non-small-cell lung cancer.

PURPOSE: To investigate the possibility of using intensity-modulated radiotherapy (IMRT) to reduce the irradiated volumes of the normal lung and other critical structures in the treatment of non-small-cell lung cancer (NSCLC) and to investigate the effect of IMRT on the potential of spreading low doses to large volumes of normal tissues in such treatment. METHODS AND MATERIALS: A retrospective treatment planning study was performed to compare IMRT and conventional three-dimensional conformal radiation therapy (3D-CRT) for 10 NSCLC patients (Stage I-IIIB). In the IMRT plans, three to nine coplanar beams were designed to treat 95% of the planning target volume with 63 Gy and to minimize the volumes of the normal lung, esophagus, heart, and spinal cord irradiated above their tolerance doses. The two types of plans were compared with respect to the planning target volume coverage, dose-volume histograms, and other dosimetric indexes of the normal structures. RESULTS: Comparing the nine-beam IMRT plan with the 3D-CRT plan, the percentage of lung volume that received >20 Gy and the mean lung dose were reduced for all cases, with a median reduction of 8% and 2 Gy, respectively. An additional reduction of the >5-Gy volume and >10-Gy volume for the lung and thoracic tissue was more difficult with IMRT, although still possible using fewer beams in IMRT. The integral dose to the entire thorax was equivalent and even reduced for 8 of 10 cases using IMRT. CONCLUSION: It is possible to reduce the volumes of low doses (such as the >10-Gy volume and >20-Gy volume) for thoracic normal tissues using IMRT. The increased integral dose and low-dose volumes can be avoided for IMRT if such concerns are addressed carefully in the inverse planning process and with optimization of the IMRT beam configuration.

Carcinoma, Non-Small-Cell Lung↗

PubMed2004

Comparative measurements of hypoxia in human brain tumors using needle electrodes and EF5 binding.

Hypoxia is known to be an important prognostic marker in many human cancers. We report the use of two oxygen measurement techniques in human brain tumors and compare these data with semiquantitative histological end points. Oxygenation was measured using the Eppendorf needle electrode and/or EF5 binding in 28 brain tumors. These data were compared with necrosis, mitosis, and endothelial proliferation. In some tumors, absolute EF5 binding was converted to tissue pO(2) based on in vitro calibrations. Eppendorf electrode readings could not be used to identify WHO grade 1/2 versus WHO grade 3/4 tumors, they could not differentiate grade 3 versus grade 4 glial-derived neoplasms, nor did they correlate with necrosis or endothelial proliferation scores. EF5 binding increased as the tumor grade increased and was significantly associated with necrosis and endothelial proliferation. There was no statistically significant correlation between the two hypoxia detection techniques, although both methods indicated similar absolute ranges of tissue pO(2). There was substantial inter- and intratumoral heterogeneity of EF5 binding in WHO grade 4 glial neoplasms. The majority of cells in glial-derived tumor had levels of hypoxia that were mild to moderate (defined herein as 10% to 0.5% pO(2)) rather than severe (defined as approximately 0.1% pO(2)). Immunohistochemical detection of EF5 binding tracks histological parameters in adult brain tumors, with increased binding associated with increasing necrosis and endothelial proliferation. The proportion of moderately to severely hypoxic cells is relatively low, even in the high-grade tumors. Human brain tumors are dominated by oxic to moderately hypoxic cells.

Adult↗

PubMed2004

Predicting radiosensitivity using DNA end-binding complex analysis.

Previous reports have suggested that measuring radiosensitivity of normal and tumor cells would have significant clinical relevance for the practice of radiation oncology. We hypothesized that radiosensitivity might be predicted by analyzing DNA end-binding complexes (DNA-EBCs), which form at DNA double-strand breaks, the most important cytotoxic lesion caused by radiation. To test this hypothesis, the DNA-EBC pattern of 21 primary human fibroblast cultures and 15 tumor cell lines were studied. DNA-EBC patterns were determined using a modified electrophoretic mobility shift assay and were correlated with radiosensitivity, as measured by SF2. DNA-EBC analysis identified a rapidly migrating ATM-containing band (identified as "band-A") of which the density correlated with SF2 (0.02 </= SF2 </= 0.41) in primary fibroblasts (r(2) = 0.77). The DNA-EBC pattern of peripheral blood lymphocytes was identical to that of fibroblasts. In addition, band-A density correlated with SF2 (0.35 </= SF2 </= 0.80) in 15 human tumor cell lines (r(2) = 0.91). Densitometry of other bands, or total DNA-EBC binding, correlated more poorly with SF2 (r(2) < 0.45). These data indicate that DNA-EBC analysis may be a practical, clinically relevant predictor of tumor and primary cell radiosensitivity.

Cell Line↗

PubMed2004

Opioid research in amphibians: an alternative pain model yielding insights on the evolution of opioid receptors.

This review summarizes the work from our laboratory investigating mechanisms of opioid analgesia using the Northern grass frog, Rana pipiens. Over the last dozen years, we have accumulated data on the characterization of behavioral effects after opioid administration on radioligand binding by using opioid agonist and antagonist ligands in amphibian brain and spinal cord homogenates, and by cloning and sequencing opioid-like receptor cDNA from amphibian central nervous system (CNS) tissues. The relative analgesic potency of mu, delta, and kappa opioids is highly correlated between frogs and other mammals, including humans. Radioligand binding studies using selective opioid agonists show a similar selectivity profile in amphibians and mammals. In contrast, opioid antagonists that are highly selective for mammalian mu, delta, and kappa opioid receptors were not selective in behavioral and binding studies in amphibians. Three opioid-like receptor cDNAs were cloned and sequenced from amphibian brain tissues and are orthologs to mammalian mu, delta, and kappa opioid receptors. Bioinformatics analysis of the three types of opioid receptor cDNAs from all vertebrate species with full datasets gave a pattern of the molecular evolution of opioid receptors marked by the divergence of mu, delta, and kappa opioid receptor sequences during vertebrate evolution. This divergence in receptor amino acid sequence in later-evolved vertebrates underlies the hypothesis that opioid receptors are more type-selective in mammals than in nonmammalian vertebrates. The apparent order of receptor type evolution is kappa, then delta, and, most recently, the mu opioid receptor. Finally, novel bioinformatics analyses suggest that conserved extracellular receptor domains determine the type selectivity of vertebrate opioid receptors.

Amphibians↗

PubMed2004

Radiosensitivity is predicted by DNA end-binding complex density, but not by nuclear levels of band components.

BACKGROUND AND PURPOSE: We previously determined that the density of a rapidly migrating DNA end-binding complex (termed 'band-A') predicts radiosensitivity of human normal and tumor cells. The goal of this study was first to identify the protein components of band-A and to determine if the protein levels of band-A components would correlate with band-A density and radiosensitivity. PATIENTS AND METHODS: DNA end-binding protein complex (DNA-EBC) protein components were identified by adding antibodies specific for a variety of DNA repair-associated proteins to the DNA-EBC reaction and then noting which antibodies super-shifted various DNA-EBC bands. Band-A levels were correlated with SF2 for a panel of primary human fibroblasts heterozygous for sequence-proven mutations in BRCA1 or BRCA2. The nuclear protein levels of band-A components were determined in each BRCA1 heterozygote by western hybridization. RESULTS: DNA-EBC analysis of human nuclear proteins revealed 10 identifiable bands. The density of the most rapidly migrating DNA-EBC band correlated closely with both BRCA-mutation status and radiosensitivity (r(2)=0.85). This band was absent in cells with homozygous mutations in their ataxia-telangiectasia-mutated protein (ATM) genes. This band was also completely supershifted by the addition of antibodies to ATM, Ku70, DNA ligase III, Rpa32, Rpa14, DNA ligase IV, XRCC4, WRN, BLM, RAD51 and p53. However, the intranuclear concentrations of these proteins did not correlate with either the SF2 or DNA-EBC density. Neither BRCA1 or BRCA2 could be detected in band-A. CONCLUSIONS: DNA-EBC analysis of human nuclear extracts resulted in 10 bands, at least six of which contained ATM. The density of one of the DNA-EBCs predicted the radiosensitization caused by BRCA haploinsufficiency, and this band contains Ku70, ATM, DNA ligase III, Rpa32, Rpa14, DNA ligase IV, XRCC4, WRN, BLM, RAD51 and p53 but not BRCA 1 or 2. The density of band-A was independent of the nuclear concentration of any of its known component.

BRCA1 Protein↗

PubMed2004

Endoscopic ultrasound after preoperative chemoradiation can help identify patients who benefit maximally after surgical esophageal resection.

BACKGROUND: We investigated whether differences in postoperative survival exist based on the presence and site of residual tumor (esophagus vs regional lymph nodes) after preoperative chemoXRT in patients with esophageal cancer. Based on these data, we reevaluated the role of EUS in identifying patients who maximally benefit from surgical esophageal resection after preoperative chemoXRT. METHODS: We studied 97 consecutive esophageal cancer patients treated with preoperative chemoXRT and a potentially curative surgical procedure between 1998 to 2001. All patients had EUS examination prior to chemoXRT and 53 had a repeat EUS examination after chemoXRT but prior to surgery. Surgical resection specimens were analyzed for absence or presence of residual tumor and its location. RESULTS: Patients with residual tumor in the esophagus (pathT1-3N0) and patients without residual tumor (pathT0N0) had similar cumulative survival (p= 0.92). Patients with residual cancer in lymph nodes showed a trend toward shorter cumulative survival compared to patients without residual tumor in lymph nodes (p= 0.086). The actuarial survival in pathN1 group was lower than pathN0 group at 1, 2, and 3 yr. Patients with significant residual lymphadenopathy detected by EUS after therapy had significantly worse postoperative survival compared to patients with no residual lymphadenopathy (p= 0.028). In eight patients, we found that reliable cytologic identification of residual malignancy was technically feasible by EUS-FNA after chemoradiation therapy. CONCLUSIONS: Following preoperative chemoXRT and surgery, patients with residual tumor in the regional lymph nodes have lower actuarial survival at 1, 2, and 3 yr after surgery, compared to patients with path CR or with residual tumor only in the esophagus. EUS and EUS-guided FNA can be helpful in identifying residual tumor in the lymph nodes after preoperative chemoXRT to select patients who benefit maximally from surgery.

Adenocarcinoma↗

PubMed2004

A deformable-model approach to semi-automatic segmentation of CT images demonstrated by application to the spinal canal.

Because of the importance of accurately defining the target in radiation treatment planning, we have developed a deformable-template algorithm for the semi-automatic delineation of normal tissue structures on computed tomography (CT) images. We illustrate the method by applying it to the spinal canal. Segmentation is performed in three steps: (a) partial delineation of the anatomic structure is obtained by wavelet-based edge detection; (b) a deformable-model template is fitted to the edge set by chamfer matching; and (c) the template is relaxed away from its original shape into its final position. Appropriately chosen ranges for the model parameters limit the deformations of the template, accounting for interpatient variability. Our approach differs from those used in other deformable models in that it does not inherently require the modeling of forces. Instead, the spinal canal was modeled using Fourier descriptors derived from four sets of manually drawn contours. Segmentation was carried out, without manual intervention, on five CT data sets and the algorithm's performance was judged subjectively by two radiation oncologists. Two assessments were considered: in the first, segmentation on a random selection of 100 axial CT images was compared with the corresponding contours drawn manually by one of six dosimetrists, also chosen randomly; in the second assessment, the segmentation of each image in the five evaluable CT sets (a total of 557 axial images) was rated as either successful, unsuccessful, or requiring further editing. Contours generated by the algorithm were more likely than manually drawn contours to be considered acceptable by the oncologists. The mean proportions of acceptable contours were 93% (automatic) and 69% (manual). Automatic delineation of the spinal canal was deemed to be successful on 91% of the images, unsuccessful on 2% of the images, and requiring further editing on 7% of the images. Our deformable template algorithm thus gives a robust segmentation of the spinal canal on CT images. The method can be extended to other structures, although it remains to be shown that chamfer matching is sufficiently robust for the delineation of soft-tissue structures surrounded by soft tissue.

Algorithms↗

PubMed2003

Treatment planning for lung cancer: traditional homogeneous point-dose prescription compared with heterogeneity-corrected dose-volume prescription.

PURPOSE: To quantify the differences in doses to target volumes and critical thoracic structures calculated by traditional homogeneous point-dose prescription and heterogeneity-corrected volume-dose prescription. METHODS AND MATERIALS: Between 1998 and 2001, 30 patients with inoperable Stage I/II non-small-cell lung cancer underwent radiation treatment planning at our institution. A commercially available convolution/superposition- based algorithm was used. Three treatment plans were calculated for each patient using identical beam geometries: one plan was generated by traditional homogeneous point-dose prescription, a second by the traditional method with heterogeneity correction, and a third by heterogeneity-corrected volume-dose prescription that would cover 95% of the planned target volume (PTV). Target volume coverage, isocenter dose, and dose uniformity in the second and third plans were compared. RESULTS: The PTV, clinical target volume (CTV), and isocenter calculated by the heterogeneity-corrected volume-dose method were equivalent to those calculated by the traditional homogeneous point-dose method with heterogeneity correction. The fraction of the PTV covered by heterogeneity-corrected volume-dose prescription was significantly greater than the fraction covered by traditional homogeneous point-dose prescription with heterogeneity correction (p = 0.05). The dose prescribed using the traditional method would have been delivered to less than 90% of the PTV in 14 of 30 patients. There was no significant difference in the maximum and minimum doses to the PTV, the CTV, or the isocenter calculated by the traditional homogeneous method with heterogeneity correction and the heterogeneity-corrected volume-dose method. There was also no significant difference in the planned volume of lung receiving greater than 20 Gy as calculated by these two methods. CONCLUSION: When compared with traditional homogeneous radiation treatment planning, heterogeneity-corrected methods produce equivalent PTV, CTV, and isocenter doses while providing superior PTV coverage.

Carcinoma, Non-Small-Cell Lung↗

PubMed2003

Effects of radiotherapy and chemotherapy on lung function in patients with non-small-cell lung cancer.

PURPOSE: To evaluate the effects of chemoradiation on objective tests of pulmonary function. MATERIALS AND METHODS: One hundred lung cancer patients treated in five protocols between 1992 and 2000 with combinations of thoracic radiotherapy (RT) and chemotherapy were evaluated with pre- and post-RT pulmonary function tests. The pulmonary function tests were analyzed for changes in measures of obstruction (forced expiratory volume in 1 s per unit of vital capacity [FEV(1)/VC]), restriction (total lung capacity [TLC]), and diffusing capacity (diffusing capacity for carbon monoxide [DLCO]). The use and timing of chemotherapy and RT, as well as patient, tumor, and treatment factors, were evaluated using univariate and multivariate analyses. RESULTS: No treatment or patient factors were significantly associated with changes in FEV(1)/VC. Chemotherapy with RT, compared with RT alone, was associated with a lower post-RT TLC (92% vs. 107%, p = 0.002). Nodal status (N2-N3 vs. N1), tumor location (central vs. peripheral), use of >/=6 treatment fields, and tumor volume >/=100 cm(3) were also associated with a significantly lower post-RT TLC. On univariate analysis, the use of any chemotherapy (p = 0.029) and the use of concurrent vs. sequential chemotherapy (p = 0.028) were predictive of a lower post-RT DLCO. Patient age >/=60 years, nodal status (N2-N3 vs. N0-N1), tumor volume >/=100 cm(3), tumor location (central vs. peripheral), and use of >/=6 treatment fields were also associated with a significantly lower post-RT DLCO. The fractional volume of irradiated normal lung correlated with the decrease in DLCO (p <0.001), with a 1.3% DLCO decline for each 1% of total lung volume that received >20 Gy. CONCLUSIONS: The addition of chemotherapy to RT significantly exacerbates the post-RT decrease in TLC and DLCO. The greatest decrease in DLCO occurs in patients treated with concurrent chemoradiation.

Adult↗

PubMed2003

Intensity-modulated radiotherapy following extrapleural pneumonectomy for the treatment of malignant mesothelioma: clinical implementation.

PURPOSE: New insight into the extent of the target volume for the postoperative irradiation of malignant pleural mesothelioma as determined during surgery has indicated that standard conformal radiotherapy (IMRT) is not sufficient for curative treatment. We describe a novel technique for implementing intensity-modulated radiotherapy (IMRT) to deliver higher doses to treat the full extent of these complex target volumes. METHODS AND MATERIALS: After extrapleural pneumonectomy, 7 patients underwent simulation, treatment planning, and treatment with IMRT to the involved hemithorax and adjacent abdomen. The target volumes encompassed the entire operative bed, including the ipsilateral mediastinum, anterior pleural reflection, and ipsilateral pericardium and the insertion of the diaphragm and crura. These were extensively marked during surgery with radiopaque markers to facilitate target delineation. RESULTS: Setup uncertainty and respiratory-dependent motion were found to be small. Coverage of the planning target volume was very good, with the crus of the diaphragm the most difficult volume to irradiate. The radiation doses to normal structures were acceptable. CONCLUSION: IMRT for treatment of malignant mesothelioma after extrapleural pneumonectomy results in more potentially curative doses to large, complex target volumes with acceptable doses to normal tissues.

Humans↗

PubMed2003

Intensity-modulated radiation therapy: a novel approach to the management of malignant pleural mesothelioma.

PURPOSE: Malignant pleural mesothelioma (MPM) causes symptoms and death mainly due to local progression, even after combined modality treatment. Poor local control after conventional radiotherapy may be due to the low dose of radiation that has been administered or to restriction of the target volume to avoid critical organs. Intensity-modulated radiation therapy (IMRT) has the potential to overcome these geometric/dosimetric constraints. METHODS AND MATERIALS: Seven patients with MPM who had an extrapleural pneumonectomy (EPP) were treated with adjuvant IMRT. The clinical target volume (CTV) included the surgically violated area inside the chest wall with particular attention to the insertion of the diaphragm, pleural reflections, and the deep margin of the thoracotomy incision. Treatment was delivered by intensity-modulated 6-MV photon beams using dynamic multileaf collimation. RESULTS: The CTV ranged from 2667 to 7286 mL. The average CTV covered to 50 Gy was 94% (range, 92% to 98%). Respiratory motion was minimal. The average volume of the boost areas covered by 60 Gy was 92% (range, 82% to 99%). Dose-volume constraints for normal tissue were met in almost all cases. Acute toxicity was mild to moderate. The most severe side effects were anorexia, nausea or vomiting, and dyspnea. Esophagitis was absent or mild. After a minimum of 13 months follow-up care there were no cases of disease recurrence within the ipsilateral hemithorax. CONCLUSION: Treatment of the extensive operative area after an EPP is feasible using IMRT. Input from the radiologist and from the surgeon in the planning process facilitates definition of the high dose volumes. In light of patients' tolerance to post-EPP IMRT, it may be feasible to incorporate systemic therapy, including novel biologic therapies into the treatment regimen.

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