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C F Hess

Publications and source records attributed to C F Hess.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effects of paclitaxel in combination with radiation on human head and neck cancer cells (ZMK-1), cervical squamous cell carcinoma (CaSki), and breast adenocarcinoma cells (MCF-7).

BACKGROUND AND PURPOSE: The anticancer drug paclitaxel, a natural product from Taxus brevifolia, is a microtubule-stabilising agent, which has been shown to block different cells in the G2/M phase of the cell cycle and so modulate their radioresponsiveness. We investigated the radiosensitizing potential of paclitaxel in human head and neck cancer cells (ZMK-1), in cervical squamous cell carcinoma cells (CaSki) and in breast adenocarcinoma cells (MCF-7). METHODS: ZMK-1 cells were incubated with paclitaxel for 3, 9, or 24 h before irradiation. ZMK-1-, CaSki- and MCF-7 cells were incubated with paclitaxel for 24 h after irradiation. The paclitaxel concentration (70 nM, 7 nM, 0.7 nM) was chosen to obtain equivalent toxicity at the different incubation times (3 h, 9 h, 24 h respectively). Radiation doses were from 0 to 8 Gy. Cell survival was measured by a standard clonogenic assay after a 9-day incubation. Flow cytometry was used to measure the capacity of paclitaxel to cause accumulation of cells in the G2/M phase of the cell cycle. RESULTS: Paclitaxel alone was cytotoxic in a time- and concentration-dependent manner. Up to 36% of the ZMK-1 cells accumulated in G2/M after treatment for 24-36 h. If the cells were incubated with paclitaxel before irradiation the isoeffect enhancement ratios for ZMK-1 cells, determined at the 37% survival level, were 0.81, 1.48 and 1.15 for 3-h, 9-h, and 24-h pre-incubations respectively. For a paclitaxel incubation of 24 h after irradiation, the isoeffect enhancement ratios, determined at the 37% survival level, were 0.72, 0.76 and 1.2 for the ZMK-1. CaSki, and MCF-7 cells respectively. CONCLUSION: In the three cell lines no radiosensitizing effect of paclitaxel could be demonstrated unambiguously. The use of asynchronized cells or the support of cellular repair mechanisms while the cells are blocked in G2/M could partly explain the results.

Adenocarcinoma↗
PubMed1999

Radiosensitizing effect of natural and recombinant beta-interferons in a human lung carcinoma in vitro.

PURPOSE: The enhancing effect of natural interferon-beta (n-IFN-beta) or recombinant interferon-beta (r-IFN-beta) on radiation damage in tumor cells has been evaluated in several sudies. It is not clear whether the different forms of IFN-beta available today are equally efficient in modulating the intrinsic radiosensitivity of tumor cells. The purpose of this study was to compare the radiosensitizing effect of n-IFN-beta, r-IFN-beta1a, and r-IFN-beta1b in one cancer cell line. METHODS: The A549 lung-cancer cell line was grown as a monolayer culture and incubated for 24 h with n-IFN-beta (Fiblaferon), r-IFN-beta1a (Betaserin), or r-IFN-beta1b (Betaferon). Thereafter, the cultures were irradiated with single graded doses of 0, 1, 2, 4, and 6 Gy. Cellular survival was counted in a colony-forming assay at 10 days after treatment. Survival curves were established using the linear quadratic model. Statistical comparison of the survival data was performed using Student's t-test for each dose point. Interactions of IFN-beta and radiation were evaluated using isobologram analysis. RESULTS: All three types of IFN-beta enhanced the radiation sensitivity of A549 cells in a similar way as shown in the alteration of the survival curves and the isobologram analysis. The isoeffective concentration of r-IFN-beta1b was 2.7-fold higher than that of r-IFN-beta1a or n-IFN-beta. All three interferons increased the alpha-component of the survival curves in a concentration-dependent way, suggesting an influence on repair of radiation damage. The maximal sensitizing enhancement ratio (SER) obtained with n-IFN-beta or r-IFN-beta1a at 3000 IU/ml was 1.66 and 1.51, respectively. The highest SER, obtained with r-IFN-beta1b, at 8000 IU/ml was 1.93. CONCLUSIONS: All three interferons tested can equally modify the intrinsic radiosensitivity of A549 cells. The isoeffective concentration of r-IFN-beta1b is 2.7-fold that of n-IFN-beta or r-IFN-beta1a.

Cell Division↗
PubMed1999

Therapeutic outcome and relation of acute and late side effects in the adjuvant radiotherapy of endometrial carcinoma stage I and II.

BACKGROUND AND PURPOSE: Adjuvant radiotherapy is the standard treatment for endometrial carcinoma. However, until now there has been no clear indication that radiotherapy in that setting improves survival. This calls for critical assessment of the relation between the expected benefit and the number and severity of postradiotherapeutic side effects. MATERIAL AND METHODS: In a retrospective study 159 consecutive patients with stage I and II endometrial carcinoma were treated with external radiotherapy and vaginal brachytherapy after hysterectomy and bilateral salpingoophorectomy (no surgical lymph node staging). Recurrence rates, survival and side effects were evaluated, in particular with regard to the relation of acute and late toxicity. RESULTS: Five percent of all patients developed a recurrence either in the abdomen or at distant locations. No pelvic relapses were diagnosed. Five-year relapse-free survival was 92% for stage IA + B, 84% for stage IC, and 79% for stage II disease. Acute toxicity was seen in 65.4% of patients, all grade 1 or 2, late toxicity grade 1 or 2 in 18.8%, grade 3 or 4 complications in 1.8%. The estimated 5-year freedom from late toxicity was 76.8%. Seventy-seven percent of all patients with treatment interruptions or premature end of therapy experienced late injury. In ten of 33 patients with late sequelae there was no free interval between early and late toxicity. No relation of radiation technique/fractionation and the rate of side effects was noticed. CONCLUSIONS: Adjuvant radiotherapy leads to excellent pelvic control, with few serious complications. Major acute toxicity shows significant correlation with the incidence of severe late injury, which we suggest to classify in part as consequential late effects.

Adult↗
PubMed1999

Accuracy of alignment in breast irradiation: a retrospective analysis of clinical practice.

The objective of the study was to determine the accuracy of patient positioning in radiotherapy for breast cancer. Portal images were obtained using a fast electronic megavoltage radiotherapy imaging system in 30 cases of breast cancer. Quantitative analysis of 530 megavolt portal images and comparison with 30 digitized simulation films were performed. Five linear measurements were taken for each simulation and verification film. Central lung distance (CLD) is the distance from the dorsomedial beam edge to the inner thoracic wall in the central plane of the beam. Cranial lung distance (CrLD) is the distance from the dorsomedial beam edge to the inner thoracic wall in the plane of the beam at 4 cm from the central plane. Central beam edge to skin distance (CBESD) is the distance from the skin to the ventrolateral beam edge in the central plane of the beam. The central irradiated width (CIW) is defined as the distance from the dorsomedial beam edge to the skin. The craniocaudal distance (CCD) is defined as the distance from a particular landmark to the caudal field border. Concerning patient position in the field, mean standard deviations of the difference between simulation and treatment images were 3.9 mm for the CLD, 3.2 mm at +4 cm, 3.6 mm for the CIW, 3.3 mm for the CBESD, 3.8 mm for the CCD. In 90% of all set-up for treatment, errors were less than 1 cm. The variation of the CLD was the largest set-up error. This parameter is clinically the most significant. Future treatment delivery should be improved by introducing patient positioning devices such as thermoplastic shells. The electronic portal imaging device (EPID) appears to be an adequate tool to study the accuracy of treatment set-ups like this.

Breast Neoplasms↗
PubMed1998

Treatment of primary malignant rhabdoid tumor of the brain: report of three cases and review of the literature.

PURPOSE: Primary malignant rhabdoid tumor (MRT) of the central nervous system is an extremely aggressive tumor predominantly related to early childhood, with characteristic histopathological findings but unclear histogenesis. Owing to its low incidence, little knowledge exists concerning the best therapeutic strategy. METHODS AND MATERIALS: Three children of our hospital with MRT of the brain underwent a maximum tumor resection followed by multidrug chemotherapy and radiation therapy to the craniospinal axis. RESULTS: Relapse was disseminated along the spinal subarachnoid spaces in one child and occurred at the primary tumor site in the other two patients. Maximum survival was 15 months from diagnosis. CONCLUSION: A review of patients reported in the literature and a comparison to our patients reveals a high propensity to early local relapse and meningeal dissemination. In the absence of more effective therapeutic options, we recommend multidisciplinary treatment of patients in good general condition and with resectable disease. In particular, following radiation therapy, tumor remissions and delay of tumor regrowth have been observed.

Brain Neoplasms↗
PubMed1998

Treatment of children with relapsed soft tissue sarcoma: report of the German CESS/CWS REZ 91 trial.

BACKGROUND: The present study was performed to evaluate the possibilities of relapse treatment in patients heavily pretreated for a soft tissue sarcoma. PATIENTS AND METHODS: Prospective, multicenter study in 44 soft tissue sarcoma (STS) patients with first relapse. Primary diagnosis was embryonal rhabdomyosarcoma (RME) in 17 patients, alveolar rhabdomyosarcoma (RMA) in 13, primitive neuroectodermal tumor (PNET) in 6, and miscellaneous soft tissue sarcomas in 8 patients. Initial chemotherapy consisted of carboplatin/etoposide combination (150 mg/m2 each, days 1 to 4) followed by local therapy including surgical treatment and, whenever possible, radiotherapy. RESULTS: In 11/17 patients without primary tumor resection, CR or PR was achieved following the initial two cycles of chemotherapy (61%). The probability of event-free survival (pEFS) for RME patients was 0.41 +/- 0.12 at 5 years, and 0.25 +/- 0.12 for RMA patients. But, in contrast no PNET patient or patient with another soft-tissue sarcoma achieved long-term remission. Additional local radiotherapy significantly (P = 0.002) improved pEFS (3-year estimates of 0.23 +/- 0.2 vs. 0.1 +/- 0.1 in patients without radiotherapy). CONCLUSIONS: In patients with RME, relapse treatment employing a carboplatin/etoposide combination may induce a second remission in approximately 40% of patients. Surgical excision and additional local radiotherapy seem to be essential to maintain a stable remission. In patients with RMA or PNET, however, this treatment strategy is of no long-term benefit.

Antineoplastic Agents, Alkylating↗
PubMed1998

Adjuvant vaginal high-dose-rate afterloading alone in endometrial carcinoma: patterns of relapse and side effects following low-dose therapy.

OBJECTIVE: This retrospective study was conducted to document the incidence and location of recurrences as well as the rate of side effects following low-dose postoperative high-dose-rate (HDR) brachytherapy in patients with endometrial carcinoma. METHODS: From 1987 to 1993, 122 patients with moderate-risk (78) and high-risk (44) endometrial carcinoma underwent adjuvant vaginal irradiation. All patients received three fractions of 7 Gy specified on the surface of the vaginal cylinder. RESULTS: Relapses occurred in 12 (9. 8%) patients on average after 25.6 months. Seven (5.7%) patients had a sole pelvic recurrence; in 2 (1.6%) of those the relapse was located in the vagina only. Three (2.5%) patients had a pelvic relapse combined with distant metastases. Distant metastases alone were diagnosed in 2 (1.6%) patients. A tumor recurrence was diagnosed in 3 of 78 (3.8%) patients with moderate-risk disease and in 9 of 44 (20.5%) patients with high-risk disease. The estimated 5-year relapse-free survival was 94% for patients with moderate-risk and 74% for patients with high-risk tumors (P = 0.004). Neither severe nor chronic complications were noted. CONCLUSION: Even low doses of HDR brachytherapy seem sufficient for excellent vaginal disease control in moderate-risk disease. In advanced tumors combined radiation therapy is warranted for improved pelvic disease control.

Aged↗
PubMed1998

Radiation rendered more cytotoxic by fludarabine monophosphate in a human oropharynx carcinoma cell-line than in fetal lung fibroblasts.

PURPOSE: Fludarabine monophosphate (fludarabine-P) is a relatively new drug in the treatment of different haematological diseases. The mechanism of action also implies a possible role of this drug as a radiosensitizer. Up to now no in vitro investigations dealing with radiosensitizing effects of fludarabine-P in carcinoma cell lines and fibroblasts have been published. The aim of our studies was to analyse the cytotoxic and radiosensitizing effects of different dosages and application schedules of fludarabine-P in a human squamous carcinoma cell line of the oropharynx (ZMK-1) and of fetal lung fibroblasts (MRC-5) in vitro. Possible mechanisms of interaction of fludarabine-P and radiation were investigated. METHODS: ZMK-1 and MRC-5 cells were cultured under standard conditions with different concentrations of fludarabine-P in combination with escalating doses of radiation. Cytotoxic effects were measured by colony-forming assays. Induction and rejoining of radiation-induced DNA double-strand breaks after incubation with fludarabine-P were measured using constant-field gel electrophoresis. Incubation times for rejoining varied from 0 h to 24 h. RESULTS: Fludarabine-P showed a radiosensitizing activity in ZMK-1 tumour cells and MRC-5 fibroblasts. The observed effects depended on the concentration and the incubation time. The largest effect was demonstrable for an incubation of 5 days, which started shortly before irradiation, whereas an incubation solely before irradiation did not have a clear effect on the cellular survival. The sensitizer enhancement ratio, at the 10% survival level, in the ZMK-1 cells was 2.2 in comparison to 1.6 in MRC-5 cells. The analysis of the interaction of fludarabine-P and ionising radiation by means of the isobologram approach, revealed an overadditive effect in the tumour cell line and an additive effect in the lung fibroblasts. Fludarabine-P did not modify the rejoining of radiation-induced DNA double-strand breaks in either cell line. CONCLUSIONS: We conclude that fludarabine-P in clinically attainable doses is a strong radiosensitizer in ZMK-1 cells and has a lower activity in the MRC-5 fibroblasts in vitro. The radiosensitization of fludarabine-P seems to be over additive in the malignant cells and additive in normal fetal fibroblasts. This would indicate that fludarabine-P might enhance the therapeutic ratio of radiation. Further investigations are warranted to identify the potential of this drug as a radiosensitizer in vivo and to elucidate the mechanism of interaction of the drug and radiation.

Carcinoma, Squamous Cell↗
PubMed1998

Induction combination chemotherapy with docetaxel and carboplatin in advanced non-small-cell lung cancer.

BACKGROUND: Results in the therapy of locally advanced non-small-cell lung cancer (NSCLC) by operation and/or irradiation only are poor. To improve the long-term prognosis a systemic induction chemotherapy may be successful in reducing local tumor burden and eliminating micrometastases. The efficacy of preoperative docetaxel-carboplatin combination chemotherapy was studied in a phase-II study for NSCLC stage IIIB. METHODS: 15 patients with functionally operable stage IIIB NSCLC (10 squamous-cell, 4 adeno, 1 large-cell) were enrolled to receive 4 cycles of docetaxel (100 mg/m2, day 1) and carboplatin (AUC 7.5, day 2) on an outpatient basis with G-CSF support after cycle 1 and were subsequently evaluated for surgery. Postoperatively the patients were irradiated with 50 Gy (R0-resection) or 60 Gy (R1-resection). RESULTS: Acceptable hematologic and non-hematologic toxicity was observed. On an intent-to-treat basis, 14 patients were evaluable for radiological response after 4 cycles of chemotherapy (1 patient still on therapy): 11/14 patients had radiological response of > or = 50%, 1/14 progressive disease, 2 exclusions because of toxic death (1 patient) and capillary leak (1 patient). Of 11 patients evaluated for surgery, 9 patients were resected, 1 patient is awaiting operation, 1 patient received radiotherapy because of an esophageal fistula. By histological findings a downstaging was achieved in 6/9 resected patients: histological complete response (CR) in 4 patients, partial response (PR) in 2, and no response in 3. With a mean follow-up of 8.1 months (excluding 1 patient in early postop course), 5/5 R0 and histological responders are alive and disease-free. Of the 3 histological non-responders, 1 patient (R1/2 resection) died of respiratory failure, 2 patients (1 R1 and 1 R0) of distant metastases. CONCLUSION: Outpatient therapy with docetaxel/carboplatin chemotherapy is effective in downstaging patients with NSCLC, toxicity is acceptable. Histological response may be the most important prognostic factor. The early results of this phase II study encourage evaluation of the long-term benefit within a prospective randomized phase III study.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Nasopharyngeal carcinoma in childhood and adolescence: concept and preliminary results of the cooperative GPOH study NPC-91. Gesellschaft für Pädiatrische Onkologie und Hämatologie.

BACKGROUND: The increasing use of chemotherapy has improved the prognosis of patients with nasopharyngeal carcinoma (NPC), and the authors demonstrated the beneficial effect of adjuvant interferon (IFN)-beta in a previous pilot study of children with advanced stage NPC. The current multi-institutional, cooperative GPOH (Gesellschaft für Pädiatrische Onkologie und Hämatologie) study NPC-91 was begun in 1992 to determine the efficacy of preradiation chemotherapy, radiotherapy, and adjuvant IFN-beta, in the treatment of advanced stage NPC. METHODS: Of a total of 22 patients, 21 had American Joint Committee on Cancer Stage III or IV disease, and 1 had Stage II disease. The median age was 12 years (range, 8-16 years). Twenty of 22 received 3 courses of preradiation chemotherapy consisting of methotrexate 120 mg/m2 on Day 1, cisplatin 100 mg/m2 on Day 1, and 5-fluorouracil 1000 mg/m2 for five days as well as 6 doses of leucovorin 25 mg/m2 every six hours beginning on Day 2. The Stage II patient received no chemotherapy, and chemotherapy was terminated for another during the first course. All patients had radiation therapy, stratified by stage. The cumulative dose to the primary sites was 59.4 gray (Gy), with single doses of 1.8 Gy. A total of 45 Gy was delivered to the neck area. Finally, all patients were treated with recombinant IFN-beta (10(5) U per kg of body weight) 3 times a week for 6 months. RESULTS: The response rate was 91%. These patients stayed in first remission during a median follow-up of 32 months. With the exception of one reversible cardiotoxicity, moderate chemotherapy-related toxicity was observed. CONCLUSIONS: In this study, patients with advanced stage NPC had a good prognosis with treatment consisting of neoadjuvant cisplatin and 5-fluorouracil, radiotherapy, and adjuvant IFN-beta. It is particularly noteworthy that distant metastases did not develop.

Adenocarcinoma, Clear Cell↗
PubMed1997

Radiotherapy and concomitant weekly 1-hour infusion of paclitaxel in the treatment of head and neck cancer--results from a Phase I trial.

PURPOSE: To define the maximum tolerated dose (MTD) by describing the dose-limiting toxicity (DLT) of weekly paclitaxel (PAC) given as a 1-h I.V. infusion in patients with head and neck cancer concomitant to irradiation. METHODS AND MATERIALS: Patients with unresectable or incompletely resected head and neck cancer were enrolled into a prospective, dose-escalating Phase I study. Toxicity was graded according to the WHO toxicity score. MTD dose was defined when two out of six patients developed DLT. The starting dose of PAC was 20 mg/m2 once weekly I.V. over 60 min, with a subsequent dose escalation of 10 mg/m2 in cohorts of three new patients. Radiation therapy was administered in three field technique over 6-7 weeks in 2.0 Gy/daily fractions for 5 consecutive days/week up to total doses of 60-70 Gy. RESULTS: From 1994-1996, 18 patients completing three dose levels were included into the study. Altogether, 101 courses of chemotherapy were evaluable for toxicity. On the second dose level (30 mg/m2) one of three patients experienced DLT with Grade IV mucositis. On the next dose level with 40 mg/m2 PAC weekly one patient experienced DLT being prolonged Grade III mucositis. From the following three patients required, two patients showed no DLT. The third patient showed mucositis of WHO Grade 4 and died from hemorrhage caused by a rupture of the a pharyngeal wall. Dose level 2 (30 mg/m2) was repeated and one of the three newly treated patients again suffered from mucositis WHO Grade 4. CONCLUSION: When PAC is given weekly as a 1-h infusion concomitant to radiotherapy, MTD is 30 mg/m2 with mucositis being DLT; hematological and further nonhematological toxicity is mild.

Adult↗
PubMed1997

Intraspinal high-grade astrocytoma in a child--rationale for chemotherapy and more intensive radiotherapy?

Intraspinal high-grade astrocytoma in children is an extremely rare tumor entity with disappointingly short survival times despite multimodality treatment. We report on a girl with anaplastic astrocytoma at level T9-11, who was treated with tumor resection, multidrug chemotherapy and irradiation. Local recurrence was diagnosed after 16 months. With reference to other cases reported in the literature, the course of disease, achievements and limitations of currently available therapeutic options, and potential future strategies are discussed.

Adolescent↗
PubMed1997

Synergistic cytotoxic effects of ether phospholipid analogues and ionizing radiation in human carcinoma cells.

BACKGROUND AND PURPOSE: There is growing evidence in recent years that the antiproliferative effects of ionizing radiation may not be exclusively mediated via DNA damage but also by interactions and alterations of cell membrane associated processes. Here, we tested the hypothesis that membrane active cytotoxic ether lipids and analogues may interact with ionizing radiation, enhancing its antiproliferative effects. MATERIALS AND METHODS: The two epithelial tumor cell lines HTB 43 and KB, and the ether lipid resistant subline KBr were treated by a combination of radiation and ether lipids. Cytotoxic effects were measured by colony forming assays and the effects on membrane phospholipids were determined by quantitative thin-layer chromatography of cell lipid extracts. RESULTS: We present evidence that some ether lipids show supra-additive cytotoxic effects with ionizing radiation. These effects seem to depend on the same structural properties of ether lipids that determine their intrinsic cytostatic and cytotoxic activity. Identical growth inhibitory results were achieved when cells were treated before, or 30 min after irradiation. Analysis of major membrane phospholipids revealed no statistically significant differences of phospholipid distribution pattern in cells exposed to both treatment modalities. CONCLUSION: Our data indicate that changes of overall membrane phospholipid composition do not seem to be the mechanism of synergistic antiproliferative activity of ether lipids and ionizing radiation.

Antineoplastic Agents↗
PubMed1996

Accuracy of field alignment in abdominal radiation therapy.

PURPOSE: To assess the accuracy of field alignment in a homogeneous group of patients undergoing radiotherapy of the abdomen (adjuvant treatment of the paraaortic region in Stage I testicular seminoma). To evaluate the predictive value of the first verification on field placement errors during subsequent treatment delivery. METHODS AND MATERIALS: In 45 patients, linear and rotational discrepancies were measured between simulation and first check and between 10 consecutive verification films. RESULTS: For the total group of patients, the distribution of all deviations showed mean values between 2.3 mm and -2.7 mm with standard deviations of 3.9 mm to 4.7 mm for linear discrepancies, and -0.5 degree to 0.3 degree with standard deviations of 1.2 degrees to 2.1 degrees for rotational discrepancies, respectively. For all patients, deviations for the transition from simulator to the treatment machine were similar to deviations during subsequent treatment delivery, with 95% of all absolute deviations < 10.0 mm and 4 degrees, respectively. When performing correlation analysis between deviations at first check and during treatment delivery, a correlation for lateral displacements and a borderline correlation for caudal displacements could be found. There was no correlation for cranial and rotational displacements. CONCLUSIONS: Although a trend of deviations for subsequent treatment delivery may be shown at first check, our analysis indicates that the first verification cannot reliably predict inaccuracies during treatment delivery. Random fluctuations of field displacements of up to 1.0 cm prevail. They must be considered when prescribing the safety margins of the planned target volume and determining cutoff points for corrective actions in abdominal radiation therapy.

Adult↗
PubMed1995

Is the standardized helmet technique adequate for irradiation of the brain and the cranial meninges?

PURPOSE: To evaluate whether the standardized helmet technique is adequate to reliably cover the clinical target volume (whole brain including cranial meninges) during treatment planning and treatment delivery. METHODS AND MATERIALS: In 21 patients undergoing irradiation of the brain in acute lymphoblastic leukemia or primary cerebral lymphoma, the coverage of the clinical target volume was checked with a repeat computed tomography (CT) in the treatment position (head fixation with face mask). The accuracy of field alignment was quantitatively assessed with sequential verification films. For each patient, linear and rotational discrepancies were measured between the simulation and first check film, and between five consecutive verification films. RESULTS: Coverage of clinical target volume. In 11 cases (52%), the CT examinations showed that parts of the subfrontal region and midcranial fossa were not included by the field assigned under simulation. Accuracy of field alignment. For the total group of patients, all deviations were normally distributed with mean values between -1.2 mm and 1.5 mm and standard deviations of 2.9 mm to 3.7 mm for linear discrepancies, and 0.3 degrees +/- 3.2 degrees for rotational discrepancies. For all patients, deviations were similar for the transition from simulation to the treatment machine and for subsequent treatment delivery, with 50% and 95% of absolute differences being less than 2.0 mm and 6.5 mm, respectively. Maximum linear deviations were less than 9.5 mm. CONCLUSIONS: The currently used helmet technique is inadequate to cover the clinical target volume. Repeat CT examinations are a useful method to delineate the clinical target volume on an individual patient basis. In addition, statistical fluctuations of field displacements up to 1.0 cm have to be considered when prescribing safety margins for reliable coverage of the clinical target volume during treatment planning and delivery.

Adolescent↗