S662 nd ESTRO Forum 2013 (VMAT).We present our clinical experience in the first patients (> 6 months follow-up) to emphasize tolerance to low dose exposure.Materials and Methods: We reviewed 198 patients (mean age 55 range 32-75): 121 were treated for left sided, 72 right sided and 5 for bilateral disease.Approximately half of the patients had an indication for lymph node irradiation.Patients were treated with an integrated boost (SIB) of 50.4/64.4Gy(n=89) or 50/#2Gy(n=32) or with 42.6/#2.66Gy(START) and 10/#2.5Gysequential boost (n=66).Sixteen patients (> 70 yrs) received 5x (+2x boost) 6.5 Gy weekly.Patients were seen weekly and at 1, 3 and 6 month after treatment.Potential risk factors for toxicity were tested in 2x2 tables (Fisher´s exact).The planning target volume dose was prescribed 95% (maximum< 108%), with objectives for respectively, ipsilateral lung (V20Gy<20-30%, V5Gy<60-65%), other lung (V5Gy<20%), heart (V10Gy<50%, V35Gy<10%) with maximum <35Gy, and contralateral breast (V5Gy<0.5-1%)withmaximum <10Gy.All dose volume comparisons were adjusted to abiological equivalent dose of 2Gy/ fraction.Results: During planning VMAT plans were often abandoned (85%) mainly because of V5, and alternative IMRT was selected for treatment.VMAT plans selected for treatment resulted in higher V10 in heart (19.7 versus 13.7%), V5 of contralateral breast (0.8 versus 0.4%) and lung V5 (66.8 versus 63.8).For bilateral, however, VMAT resulted in better dose distributions.One bilateral treatment consistedof SIB, all others of START, being easier to set up and better tolerated.Almost no dermatitis (13% grade 2) or cosmetic deterioration was observed.Dry cough was observed in 18% of patients and 8 patients) needed medication (pneumonitisgrade 2 RTOG).Plans were reviewed and those patients with dry cough showed oftenlung V5 over 70%.Among other risk factors tested (table 1) lung V5 exposure over 70% appeared strongly associated with pneumonitis.After the first analysis, we decided to not accept any planning with V5 over 70% and no new clinical pneumonitis has appeared since.

Introduction: For the further development of biological imaging for radiotherapy it is crucial that marker development focuses on parameters that are relevant for local tumor control after fractionated irradiation. Outcome after fractionated irradiation is determined by a complex of different factors which can be summarized as the 5 R's of fractionated radiotherapy, i.e. repopulation, reoxygenation, recovery from sublethal damage, redistribution and intrinsic radiation sensitivity.

Purpose: To assess the effect of single-dose irradiation on intercellular adhesion molecule 1 (ICAM-1) expression in the urothelium of mouse urinary bladder and to correlate ICAM-1 variations with fluctuations in storage capacity during the early and late radiation response.Materials and methods: Groups of female C3H mice were subjected to irradiation with either 20 or 0 Gy. The intensity of immunohistochemical ICAM-1 staining in the urothelium was assessed in a semiquantitative way applying an arbitrary score (0-5). Changes in bladder storage function were assessed by transurethral cystometry.Results: For the early radiation response phase, a reduction in bladder capacity by >50%, i.e. a positive functional radiation response, was seen in 40% of the irradiated animals between days 0 and 15, and in 64% of animals during days 16-30. During the late response phase, 71% of the animals sacrificed after day 180 developed a positive functional response. Urothelial cells were found to express ICAM-1 constitutively. Irradiation resulted in an early rise in staining signal by day 2, with a maximum on day 4 and a return to control values on day 13. A permanent increase in ICAM-1 staining signal was observed in the late phase, from day 90 to 360 after irradiation. The expression of ICAM-1 in animals with a positive late response was 4.2+/-1.2 (mean+/-standard deviation), compared with 2.6+/-1.0 in non-responders (p=0.0009).Conclusion: Irradiation induces significant acute and chronic changes in urothelial ICAM-1 expression indicating that the urothelium contributes to the pathogenesis of both acute and late radiation effects in the urinary bladder.

BACKGROUND:Inhibition of the vascular endothelial growth factor receptor (VEGFR) has been shown to improve the radiation response of several experimental tumors. The present experimental study compares the effect of neoadjuvant, concomitant and adjuvant treatment with PTK787/ZK222584, a specific inhibitor of the VEGFR, in combination with fractionated irradiation.MATERIALS AND METHODS:Growth delay after daily oral application of 50 mg per kg bodyweight PTK787/ZK222584 or carrier was tested in five different human squamous cell carcinoma growing in nude mice. Two of these tumor models, a responder (UT-SCC-14) and a non-responder (FaDu), were selected for the irradiation experiments (15 fractions of 2 Gy within 15 days). PTK787/ZK222584 was applied daily for 4-18 days and stopped before start of irradiation (neoadjuvant), for 15 days during fractionated irradiation (concomitant) or for 45 days after the course of irradiation (adjuvant).RESULTS:Adjuvant application of PTK787/ZK222584 after fractionated irradiation retarded regrowth of UT-SCC-14 tumors and, surprisingly, also of FaDu tumors which did not respond to the agent when given alone. No effects on radiation response were observed after short-term neoadjuvant or concomitant PTK787/ZK222584 application.CONCLUSION:Combined with fractionated irradiation, only adjuvant application of PTK787/ZK222584 retarded regrowth of UT-SCC-14 and FaDu tumors. The data suggest that preirradiated vasculature might be more sensitive to VEGFR inhibition compared to unirradiated vasculature. Whether the effect of adjuvant VEGFR inhibition on growth delay translates into improved local tumor control after irradiation needs further investigation.

Acceleration of clonogen repopulation during fractionated irradiation after about 3 weeks has been demonstrated previously in FaDu human squamous cell carcinoma in nude mice (Petersen et al., Int. J. Radiat. Oncol. Biol. Phys. 51, 483-493, 2001). Selection of genetically distinct, rapidly proliferating clones might contribute to this phenomenon. To address this question, three sublines (R1-R3) were established from FaDu tumors that recurred locally after fractionated irradiation. The tumors were retransplanted and irradiated under clamp hypoxia with single doses or with 18 X 3 Gy within 18 days or 36 days, followed by graded top-up doses. The results were compared with data obtained after the same treatment schedules in the parental tumor line. Histologies, tumor volume doubling times, and potential doubling times of FaDu sublines R1-R3 were not different from those of the parental line. The radiation dose required to control 50% of the tumors (TCD50) after single-dose irradiation of 37-38 Gy was the same for the FaDu sublines R1-R3 and the parental tumor. The top-up TCD50 values for the FaDu sublines R1-R3 after 18 fractions within 36 days were 14-17 Gy higher than those after 18 fractions within 18 days, indicating significant repopulation. The magnitude of this effect was not significantly different between the sublines R1-R3 or between these sublines and the parental FaDu tumors. The results indicate that selection of genetically distinct, rapidly proliferating clones does not contribute to the acceleration of repopulation during fractionated irradiation in poorly differentiated FaDu tumors. (C) 2003 by Radiation Research Society.

Purpose : To investigate the effect of BIBX1382BS, an inhibitor of the epidermal growth factor receptor tyrosine kinase, on proliferation and clonogenic cell survival of FaDu human squamous cell carcinoma in vitro , and on tumour growth and local tumour control after fractionated irradiation over 6 weeks in nude mice. FaDu human squamous cell carcinoma is epidermal growth factor receptor positive and significant repopulation during fractionated irradiation was demonstrated in previous experiments.Materials and methods : Receptor status, receptor phosphorylation, cell cycle distribution, cell proliferation and clonogenic cell survival after irradiation were assayed with and without BIBX1382BS (5 mu M) in vitro . Tumour volume doubling time, BrdUrd and Ki67 labelling indices and apoptosis were investigated in unirradiated tumours growing in NMRI nude mice treated daily with BIBX1382BS (50 mg kg(-1) body weight orally) or carrier. Tumour growth delay and dose-response curves for local tumour control were determined after irradiation with 30 fractions within 6 weeks.Results : BIBX1382BS blocked radiation-induced phosphorylation of the epidermal growth factor receptor and reduced the doubling time of FaDu cells growing in vitro by a factor of 4.9 ( p =0.008). Radiosensitivity in vitro remained unchanged after incubation with BIBX1382BS for 3 days and decreased moderately after 6 days ( p =0.001). BIBX1382BS significantly reduced the volume doubling time of established FaDu tumours in nude mice by factors of 2.6 when given over 15 days ( p <0.001) and 3.7 when applied over 6 weeks ( p <0.001). When given simultaneously to fractionated irradiation, growth delay was significantly prolonged by an average of 33 days ( p =0.003). Local tumour control was not improved by BIBX1382BS. The radiation doses necessary to control 50% of the tumours locally were 63.6 Gy (95% confidence interval 55; 73) for irradiation alone and 67.8 Gy (60; 77) for the combined treatment ( p =0.5).Conclusions : Despite clear antiproliferative activity in rapidly repopulating FaDu human squamous cell carcinoma and significantly increased tumour growth delay when combined with fractionated irradiation, local tumour control was not improved by BIBX1382BS. The results do not disprove that epidermal growth factor receptor inhibition might enhance the results of radiotherapy. However, the results imply that further preclinical investigations using relevant treatment schedules and appropriate endpoints are necessary to explore the mechanisms of action and efficacy of such combinations.

PURPOSE:To investigate the impact of the tumour bed effect (TBE) on histological parameters of the micromilieu, radiobiological hypoxic fraction and local control after fractionated irradiation in FaDu squamous-cell carcinoma in the nude mouse. This tumour has previously shown a clear-cut TBE caused by increased necrotic cell loss at a constant cell production rate in the viable tumour compartment.MATERIALS AND METHODS:Human FaDu tumours were studied in the NMRI nude mouse. Tumours were transplanted either into unirradiated subcutaneous (s.c.) tissues (controls) or s.c. tissues pre-irradiated with 12.5 Gy (TBE group). In both groups we measured the volume doubling time (VDT), potential doubling time (T(pot)), relative necrotic area, and in the viable tumour compartment the relative vascular area (9F1 mAb), relative hypoxic area (NITP or pimonidazole), relative perfused area (Hoechst 33342), and the perfused fraction of vasculature. The tumour control dose 50% (TCD 50), radiobiological hypoxic fraction (rHF) and dose-modifying factors (DMF) for the comparison of tumours in the TBE and control groups were determined from local tumour control data after treatment with single doses under ambient conditions or under clamp hypoxia, and after irradiation with 30 fractions under ambient conditions within 6 weeks using maximum-likelihood analysis.RESULTS:A clear-cut TBE (VDT = 4.0 days (95%CI 2.9;4.4) for the control group versus 7.2 days (6.4;8.9) for the TBE group; p <0.0001) caused by increased necrosis (mean relative necrotic area of 12% (5;20)) versus 33% (10;41); p = 0.07) at a constant cell production rate (T(pot) = 2.2 days (1.4;2.3) versus 2.2 days (1.7;2.6); p = 0.30) was confirmed. Histological analysis of the micromilieu within the vital subarea revealed no systematic differences between the TBE and control groups. The rHF of 2% (0.1;27) for control tumours was lower than the 15% (95% CI 2;91) for the TBE group, but this difference was nonsignificant (p = 0.12). Compared with control tumours, the TCD50 for irradiation under clamped hypoxia was in a statistical trend lower for tumours in the TBE group (DMF 1.11 (0.98;1.28), p = 0.09). After fractionated irradiation, tumours of the TBE group were significantly more radiosensitive (TCD50 56.6 Gy (46;70) versus 78.7 Gy (63;100); p = 0.003).CONCLUSIONS:The results on FaDu tumours growing in pre-irradiated tissues indicate that increased necrosis caused by impairment of the vascular supply may increase the radiosensitivity of tumours treated by fractioned irradiation.