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Biomedical subjects

John M Buatti

Publications and source records attributed to John M Buatti.

At least 19 recordsLinked to original sources
PubMed2006

Optimal number of beams for stereotactic body radiotherapy of lung and liver lesions.

PURPOSE: The aim of this study was to determine the optimal number of coplanar and noncoplanar external beams in the setting of stereotactic body radiotherapy (SBRT). METHODS AND MATERIALS: Spherical targets were delineated within 2 separate extracranial sites, the lung and liver, with diameters varying from 2 cm to 7 cm to cover the range of volumes used in SBRT. Treatment plans were created for all target volumes using 5 to 15 geometrically optimized coplanar and noncoplanar conformal beams. Dose gradient and normal tissue complication probability (NTCP) were evaluated for each set of beam configurations and for each target size. RESULTS: For all lung and liver target volumes, the dose gradient improved with an increase in beam number from 5 to 15 for both coplanar and noncoplanar beam configurations. NTCP decreased as the beam number increased from 5 to 9 beams for all target sizes for both coplanar and noncoplanar beams. There is no significant improvement in NTCP when more than 9 beams were used for treatment planning regardless of target size. CONCLUSION: Based on dosimetric criteria, the optimal number of external beams is 13 to 15 for SBRT using either coplanar or noncoplanar beam bouquets. Simple biologic models indicate that the optimal number of beams is 9 for SBRT of lung and liver lesions >2 cm, whereas smaller lesions may benefit from plans using up to 13 beams.

Algorithms↗
PubMed2006

Radiation induced adult medulloblastoma: a case report.

Adult medulloblastoma is a rare intracranial tumor. Our patient is a 61 year old woman treated with cranial irradiation 15 years previously for a low grade astrocytoma in the left posterior temporal lobe that was recently diagnosed with medulloblastoma in the right cerebellum. This is the first reported case of radiation induced adult medulloblastoma.

Astrocytoma↗
PubMed2006

Radiotoxicity after conformal radiation therapy for benign intracranial tumors.

Acoustic schwannomas, skull base meningiomas, and pituitary adenomas are benign intracranial tumors frequently managed with radiotherapy. Control rates after treatment for each of these tumors are generally high, and toxicity from treatment is relatively low. Side effect profiles depend on the tumor location, the volume treated, the dose delivered, and the presence of nearby critical structures. In addition, patient-specific factors, such as hypertension and diabetes, may increase a patient's risk for complications. This article reviews radiotoxicity after conformal radiation therapy for acoustic schwannomas, skull base meningiomas, and pituitary adenomas.

Brain Neoplasms↗
PubMed2006

Changing failure patterns in oropharyngeal squamous cell carcinoma treated with intensity modulated radiotherapy and implications for future research.

OBJECTIVE: Review the University of Iowa experience with intensity modulated radiation treatment (IMRT) in oropharyngeal squamous cell carcinoma. METHODS: From January 2000 to July 2004, 66 patients with oropharyngeal cancer were treated with IMRT, 62 with definitive IMRT and 4 postoperative IMRT. Three target volumes (CTV1, CTV2, and CTV3) were defined. The prescribed doses to CTV1, CTV2, and CTV3 were 70 to 74 Gy, 60 Gy, and 54 Gy, respectively, for definitive IMRT, and 60 to 66 Gy, 60 Gy, and 54 Gy, respectively, for postoperative IMRT. RESULTS: Median follow-up was 27.3 months and all living patients had a follow-up of at least 11.5 months. The 3-year estimate of locoregional progression free survival was 98.8%. However, there is a high incidence of distant metastasis with a 3-year estimate of distant metastasis-free survival of 80.4%. In addition, there is a high incidence of second primary tumor. The 3-year overall survival and 3-year disease-free survival were 78.1% and 64.4%, respectively. Treatment was well tolerated with 1 death resulting from treatment toxicity. CONCLUSIONS: IMRT offers an excellent locoregional control for oropharyngeal cancer patients. Failure patterns have changed with an increased portion of patients who failed distantly, either with metastasis or second primary tumor. Therefore, survival for these patients is still poor. Future research should focus on identifying patients at high risk of distant diseases and developing effective systemic treatment and prevention for distant diseases.

Adult↗
PubMed2006

Serial therapy-induced changes in tumor shape in cervical cancer and their impact on assessing tumor volume and treatment response.

OBJECTIVE: The purpose of this study was to evaluate the patterns and distribution of tumor shape and its temporal change during radiation therapy (RT) in cervical cancer and the effect of tumor configuration changes on the correlation between region of interest (ROI)-based and diameter-based MRI tumor measurement. MATERIALS AND METHODS: Serial MRI examinations (T1-weighted and T2-weighted images) were performed in 60 patients (age range, 29-75 years; mean, 53.3 years) with advanced cervical cancer (stages IB2-IVB/recurrent) who were treated with RT at four time points: start of RT, during RT (at 2-2.5 and at 4-5 weeks of RT), and post-RT. Tumor configuration was classified qualitatively into oval, lobulated, and complex based on MR film review. Two methods of tumor volume measurement were compared: ellipsoid computation of three orthogonal diameters (diameter based) and ROI volumetry by delineating the entire tumor volume on the MR workstation (ROI based). Temporal changes of tumor shape and the respective tumor volumes measured by the two methods were analyzed using linear regression analysis. RESULTS: Most tumors (70%) had a non-oval (lobulated and complex) shape before RT and became increasingly irregular during and after RT: 84% at 2-2.5 weeks of RT (p = 0.037), 86% (p = 0.025) at 4-5 weeks, and 96% post-RT (p = 0.010), compared with 70% pre-RT. Diameter-based and ROI-based measurement correlated well before RT (r = 0.89) but not during RT (r = 0.68 at 2-2.5 weeks, r = 0.67 at 4-5 weeks of RT). CONCLUSION: Most cervical cancers are not oval in shape pretherapy, and they become increasingly irregular during and after therapy because of nonconcentric tumor shrinkage. ROI-based volumetry, which can optimally measure irregular volumes, may provide better response assessment during treatment than diameter-based measurement.

Adenocarcinoma↗
PubMed2005

Intensity-modulated radiation treatment for head-and-neck squamous cell carcinoma--the University of Iowa experience.

PURPOSE: To review the University of Iowa experience with intensity-modulated radiotherapy (IMRT) in the treatment of head-and-neck squamous cell carcinoma. METHODS AND MATERIALS: From October 1999 to April 2004, 151 patients with head-and-neck squamous cell carcinoma were treated with IMRT for curative intent. One patient was lost to follow-up 2 months after treatment and therefore excluded from analysis. Of the remaining 150 patients, 99 were treated with definitive IMRT, and 51 received postoperative IMRT. Sites included were nasopharynx, 5; oropharynx, 56; larynx, 33; oral cavity, 29; hypopharynx, 8; nasal cavity/paranasal sinus, 8; and unknown primary, 11. None of the patients treated with postoperative IMRT received chemotherapy. Of 99 patients who had definitive IMRT, 68 patients received concurrent cisplatin-based chemotherapy. One patient received induction cisplatin-based chemotherapy, but no concurrent chemotherapy was given. Three clinical target volumes (CTV1, CTV2, and CTV3) were defined. The prescribed doses to CTV1, CTV2, and CTV3 in the definitive cohort were 70-74 Gy, 60 Gy, and 54 Gy, respectively. For high-risk postoperative IMRT, the prescribed doses to CTV1, CTV2, and CTV3 were 64-66 Gy, 60 Gy, and 54 Gy, respectively. For intermediate-risk postoperative IMRT, the prescribed doses to CTV1, CTV2, and CTV3 were 60 Gy, 60 Gy, and 54 Gy. RESULTS: The median follow-up was 18 months (range, 2-60 months). All living patients were followed for at least 6 months. There were 11 local-regional failures: 7 local failures, 3 regional failures, and 1 failure both in the primary tumor and regional lymph node. There were 16 patients who failed distantly, either with distant metastasis or new lung primaries. The 2-year overall survival, local progression-free survival, locoregional progression-free survival, and distant disease-free survival rates were 85%, 94%, 92%, and 87%, respectively. The median time from treatment completion to local-regional recurrence was 4.7 months (range, 1.8 to 15.6 months). Only one marginal failure was noted in a patient who had extensive tonsil cancer with tumor extension into the orbit and cavernous sinus. Patients with oropharyngeal cancer did significantly better than patients with oral cavity and laryngeal cancer, with a 2-year local-regional control rate of 98%, compared with 78% for oral cavity cancer and 85% for laryngeal cancer (p = 0.005). There was no significant difference in local-regional control for patients who received postoperative radiation or definitive radiation (p = 0.339) and for patients who had chemotherapy or not (p = 0.402). Neither T stage nor N stage had a significant effect on local-regional control (p = 0.722 and 0.712, respectively). CONCLUSIONS: Our results have confirmed the effectiveness of IMRT in head-and-neck cancer. It offers excellent outcomes in local-regional control and overall survival. More studies are necessary to further improve the outcomes of laryngeal cancer as well as oral cavity cancer.

Adult↗
PubMed2005

The role of FDG PET in management of neck metastasis from head-and-neck cancer after definitive radiation treatment.

PURPOSE: The role of neck dissection after definitive radiation for head-and-neck cancer is controversial. We select patients for neck dissection based on postradiation therapy (post-RT), computed tomography (CT), and [18F] fluorodeoxyglucose positron emission tomography (FDG PET). We summarize the clinical outcomes of patients treated with this policy to further elucidate the role of FDG PET in decision making for neck dissection after primary radiotherapy. METHODS AND MATERIALS: Between December 1999 and February 2004, 53 eligible patients were identified. These patients had stage N2A or higher head-and-neck squamous cell carcinoma and had complete response of the primary tumor after definitive radiation with or without chemotherapy. PET or computed tomography (CT) scans were performed within 6 months after treatment. Neck dissection was performed in patients with residual lymphadenopathy (identified by clinical examination or CT) and a positive PET scan. Those without residual lymph nodes and a negative PET were observed without neck dissection. For patients with residual lymphadenopathy, but a negative PET scan, neck dissection was performed at the discretion of the attending surgeon and decision of the patient. There was a total of 70 heminecks available for analysis (17 patients had bilateral neck disease). RESULTS: There were 21 heminecks with residual lymphadenopathy identified on CT imaging or clinical examination and negative PET. Of these, 4 had neck dissection and were pathologically negative. The remaining 17 were observed without neck dissection. There was a total of 42 heminecks without residual lymph nodes on post-RT CT imaging or clinical examination with a negative PET. They were also observed without neck dissection. Seven heminecks had a positive PET scan and residual lymphadenopathy. Six of them had neck dissection and 1 had fine-needle aspiration of a residual node; 3 contained residual viable cancer and 4 were pathologically negative. At median follow up of 26 months (range, 12-57 months), no regional failure was identified. The negative predictive value of PET was 100% and positive predictive value was 43%. CONCLUSION: For patients who have no evidence of residual lymphadenopathy and a negative FDG PET scan 12 weeks after definitive radiation, neck dissection can be safely withheld. Even in cases in which small residual lymphadenopathy was observed, regional recurrences have not occurred when the post-RT PET scan was negative and neck dissection was withheld. For patients with large residual lymphadenopathy (greater than 2.0-3.0 cm in size) but a negative post-RT FDG PET, further studies with longer follow-up are necessary to determine the appropriateness of withholding neck dissection.

Adult↗
PubMed2005

Initial clinical experience with frameless radiosurgery for patients with intracranial metastases.

PURPOSE: To review the initial clinical experience with frameless stereotactic radiosurgery (SRS) for treating intracranial metastatic disease. METHODS AND MATERIALS: Sixty-four patients received frameless SRS for intracranial metastatic disease. Minimum follow-up was 6 months with none lost to follow-up. Patients had a median of 2 metastases and a maximum of 4. The median number of isocenters was 2 with median arcs of 10 and median dose of 17.5 Gy. Thirteen patients were treated for progressive/recurrent disease after surgical resection or whole brain radiotherapy (WBRT). Fifty-one patients were treated with frameless SRS as an an adjunct to initial treatment. Of the total treated, 17 were treated with SRS alone, 20 were treated with WBRT plus SRS, 16 were treated with surgical resection plus SRS, and the remaining 11 were treated with surgical resection plus WBRT plus SRS. RESULTS: With a median actuarial follow-up period of 8.2 months, ultimate local control was 88%. The median time to progression was 8.1 months. The median overall survival was 8.7 months. Of the 17 patients treated with SRS alone, 86% had ultimate local control with mean overall survival of 7.1 months. Of the 13 patients who received surgical resection plus SRS without WBRT as primary treatment, there was 85% ultimate local control with an overall survival of 10.3 months. Three patients treated with initial surgery alone had recurrence treated with SRS 2-3 months after resection. All these patients obtained local control and median survival was >10 months. Of the 13 patients who received WBRT followed by SRS as boost treatment, 92% had local control and mean overall survival was 7.3 months. Of 7 patients who received SRS after recurrence after WBRT, 100% had local control with median survival of 8.2 months. For 8 patients who received surgery followed by WBRT and SRS, local control was 50%; however, ultimate intracranial control was achieved in 7 of 8 patients with repeat SRS and surgical resection. The overall survival in this group of patients was 14.7 months. No patient had a serious (Grade 3 or higher) complication requiring intervention. CONCLUSIONS: Frameless optically guided radiosurgery is less invasive, can be performed as a standard radiotherapy-based simulation procedure, and maintains submillimetric accuracy. Our initial results with frameless SRS for metastatic disease suggest survival times and local control (88%) eqiuvalent to frame-based methodologies. Practical noninvasive delivery makes treatment and potential retreatment to avoid WBRT more feasible.

Adult↗
PubMed2005

Long-term quality of life for surgical and nonsurgical treatment of head and neck cancer.

OBJECTIVE: To compare the long-term, health-related quality-of-life outcomes in patients with advanced head and neck cancer (HNC) treated with surgery and postoperative radiation therapy (SRT) or concurrent chemotherapy and radiation therapy (CRT). DESIGN: Matched-pair study comparing patients with advanced HNC treated with SRT or CRT at least 12 months after treatment. Patients completed 2 validated surveys addressing HNC-specific outcomes and depressive symptoms and provided information on employment and tobacco and alcohol use. Results for the 2 groups were compared using paired-sample t test and chi2 analysis. SETTING: University-based study. PATIENTS: Patients with stage III or IV squamous cell carcinoma of the oropharynx, hypopharynx, and larynx who underwent SRT or received CRT. MAIN OUTCOME MEASURES: Head and neck cancer-specific health-related quality of life from the Head and Neck Cancer Inventory and level of depressive symptoms from the Beck Depression Inventory. RESULTS: The matching process resulted in 27 patients in each treatment group. The HNC-specific domain scores (with higher scores representing better outcomes) for CRT vs SRT were eating, 37.8 vs 40.8 (P = .69); speech, 65.1 vs 56.0 (P = .23); aesthetics, 80.3 vs 69.2 (P = .14); and social disruption, 69.7 vs 70.6 (P = .90). Overall health-related quality of life was 64.0 with SRT and 55.0 with CRT (P = .142). For the Beck Depression Inventory (with higher scores representing worse outcomes), patients who underwent SRT had a mean score of 9.6 compared with 11.6 for patients who received CRT (P = .42). CONCLUSION: As nonsurgical means of treating HNC have become more aggressive and surgical techniques have become more focused on function preservation and rehabilitation, the overall health-related quality of life resulting from these different approaches is similar.

Combined Modality Therapy↗
PubMed2005

Atypical teratoid/rhabdoid tumor case report: treatment with surgical excision, radiation therapy, and alternative medicines.

Intracranial atypical teratoid/rhabdoid tumors (AT/RT) are rare with a poor prognosis. We report one case of a 7-year old girl living over 17 months after the diagnosis of AT/RT in the left frontal lobe. Treatment was partial surgical resection and post-operative radiation therapy. Radiation therapy resulted in complete response with no evidence of residual or recurrent disease more than 17 months after diagnosis. The patient has been maintained on an extensive regimen of alternative therapies since completion of radiation therapy.

Brain Neoplasms↗
PubMed2005

Optically guided patient positioning techniques.

Optical tracking determines an object's position by measuring light either emitted or reflected from the object. The hallmark of optical tracking systems is their high spatial resolution and measurement in real time; such systems can resolve the position of a point source within a fraction of a millimeter and report at a rate of 10 Hz or faster. Several systems have been developed for radiation therapy, all of which track infrared markers attached to the patient's external surface. The positions of the optical markers relative to the target volume, together with the desired marker positions relative to treatment isocenter, are determined during computed tomography simulation. In the treatment room, the real marker positions are measured relative to isocenter; rigid-body mathematics then determine marker displacements from their desired positions and hence target displacement from isocenter. Real-time feedback allows one to correct the patient's position. The first systems were used for intracranial stereotaxis radiotherapy; rigid arrays of optical markers were attached to the patient via a biteplate linkage. Subsequent systems for extracranial radiotherapy tracked external markers to determine patient position and/or gate the radiation beam based on patient motion. Lastly, optical tracking has been integrated with ultrasound or stereoscopic x-ray imaging to determine the position of internal anatomy targets relative to isocenter.

Humans↗
PubMed2005

Merkel cell carcinoma: two case reports focusing on the role of fluorodeoxyglucose positron emission tomography imaging in staging and surveillance.

BACKGROUND: Merkel cell carcinoma (MCC) is a rare skin neuroendocrine carcinoma frequently occurring in the head and neck area. It is known for being a locally aggressive disease with a high incidence of regional and distant metastases. Accurate initial staging and close surveillance are critical in the management of the disease. METHODS AND RESULTS: Two cases of MCC are reported in which fluorine-18-fluorodeoxyglucose positron emission tomography (FDG PET) imaging has been beneficial in directing management and predicting clinical course. Pretreatment FDG PET scans detected metastatic disease in subcentimeter lymph nodes that were not appreciated in initial computed tomography images. Posttreatment FDG PET scans predicted response to therapy with the level of FDG uptake correlating in both areas of complete response to treatment and areas of residual diseases. Finally, FDG PET imaging also detected the progression of the disease after initial treatment. CONCLUSION: FDG PET imaging is a very sensitive modality in staging, assessment of treatment response, and surveillance of MCC. Because of the rarity of MCC, multicenter study is warranted to accumulate enough cases to determine the sensitivity and specificity of FDG PET in staging and surveillance of MCC, and the impact on the management and treatment outcome.

Aged↗
PubMed2004

Value of FDG PET in assessment of treatment response and surveillance in head-and-neck cancer patients after intensity modulated radiation treatment: a preliminary report.

PURPOSE: [(18)F] fluorodeoxyglucose positron emission tomography (FDG PET) imaging has been shown to be valuable in early detection of persistent and recurrent head-and-neck cancer after treatment. Previous studies have reported its use in patients treated with conventional radiation. Many patients are now treated with intensity-modulated radiation treatment (IMRT). We evaluated the value of FDG PET in the assessment of treatment response and surveillance in head-and-neck cancer patients treated with IMRT. METHODS AND MATERIALS: We performed a retrospective review of 85 head-and-neck cancer patients treated with IMRT at our institution between December 2000 and September 2003 who had FDG PET in their follow-up. Of these, 58 were treated with primary IMRT with or without chemotherapy, and 27 were treated with postoperative IMRT. RESULTS: Sixty-four patients had negative initial FDG PET after treatment. Forty of them, who had 6 to 24 months of follow-up after the imaging study, had no evidence of local or regional recurrence, although three of them developed distant disease. Twenty-one patients had a positive initial FDG PET after treatment, with 11 positive at the primary site, 9 positive in the neck, and 3 positive distantly. Six of 11 patients with a positive FDG PET at the primary site were true positive, and 3 had salvage surgery. Eight of 9 patients positive in the neck had a salvage neck dissection. One had fine needle aspiration of the lymph node with positive cytology but refused surgery later. For patients with follow-up of 6 months and longer, only 1 of 45 patients with a negative initial FDG PET at the primary site developed a local recurrence. None of 49 patients with a negative initial FDG PET in the neck developed a regional recurrence. Two cases are presented in which abnormal FDG PET preceded laryngoscopy or computed tomography in detection of tumor recurrences. CONCLUSIONS: FDG PET is useful in the posttreatment management of head-and-neck cancer patients treated with IMRT. It is highly accurate in the detection of persistent and recurrent disease after treatment and allows salvage treatment to be initiated in a timely manner. It also provides prognostic information concerning the risk of recurrence after curative therapy.

Adult↗
PubMed2004

The role of post-radiation therapy FDG PET in prediction of necessity for post-radiation therapy neck dissection in locally advanced head-and-neck squamous cell carcinoma.

PURPOSE: The role of neck dissection after radiation therapy ([RT] with or without chemotherapy) for regionally advanced head and neck cancer is controversial. As much as 50% of residual lymphadenopathy after radiation has no viable tumor cells present on histopathologic analysis. [(18)F] fluorodeoxyglucose positron emission tomography (FDG PET) imaging can detect metabolically active cancer. This study examines the ability of post-RT FDG PET imaging to predict the tumor status of residual lymphadenopathy after nonsurgical management of regionally advanced neck disease. METHODS AND MATERIAL: From February 2000 to October 2002, 41 patients were treated definitively by radiation (with or without chemotherapy) and underwent FDG PET and computed tomography (CT) imaging after treatment to assess response. Patients with negative CT and FDG PET scans were observed and did not undergo neck dissection. Patients with radiographically persistent lymphadenopathy underwent either neck dissection or fine-needle aspiration of the lymph nodes using ultrasound guidance. The results of the FDG PET scans were correlated with the pathologic findings. RESULTS: Twelve patients with persistent lymphadenopathy underwent either neck dissection or fine-needle aspiration. Four of the 12 were found to have viable residual tumor in the cervical lymph nodes. The pathology did not correlate with the size of the lymph nodes in the pre-RT or post-RT CT studies. However, the pathology correlated strongly with the post-RT FDG PET studies. All patients with a negative post-RT FDG PET or those with a maximum standardized uptake value (SUV(max)) of less than 3.0 in the post-RT FDG PET were found to be free of residual viable tumor. Using an SUV(max) of less than 3.0 as the criterion for a negative FDG PET study, the negative predictive value was 100% and the positive predictive value was 80%. CONCLUSIONS: A negative post-RT FDG PET scan is very predictive of negative pathology in neck dissection or fine-needle aspiration even with large residual lymphadenopathy. Therefore, if the post-RT FDG PET scan is negative, neck dissection might not be required for regional control. A prospective study with longer follow-up and greater patient numbers is needed to determine whether a policy of deferring neck dissection based on a negative FDG PET is supported.

Adult↗
PubMed2004

Geometrically based optimization for extracranial radiosurgery.

For static beam conformal intracranial radiosurgery, geometry of the beam arrangement dominates overall dose distribution. Maximizing beam separation in three dimensions decreases beam overlap, thus maximizing dose conformality and gradient outside of the target volume. Webb proposed arrangements of isotropically convergent beams that could be used as the starting point for a radiotherapy optimization process. We have developed an extracranial radiosurgery optimization method by extending Webb's isotropic beam arrangements to deliverable beam arrangements. This method uses an arrangement of N maximally separated converging vectors within the space available for beam delivery. Each bouquet of isotropic beam vectors is generated by a random sampling process that iteratively maximizes beam separation. Next, beam arrangement is optimized for critical structure avoidance while maintaining minimal overlap between beam entrance and exit pathways. This geometrically optimized beam set can then be used as a template for either conformal beam or intensity modulated extracranial radiosurgery. Preliminary results suggest that using this technique with conformal beam planning provides high plan conformality, a steep dose gradient outside of the tumour volume and acceptable critical structure avoidance in the majority of clinical cases.

Computer Simulation↗