Abstract Book

S181

ESTRO 37

Conclusion Preoperative chemoradiation is a complex treatment which allows several administration strategies and possibilities intensifications offering opportunities to tailor the treatment according to tumor presentation

consider the technical aspects that may impact on trial results and the translation of those results into wider clinical practice. In this presentation we will consider issues of plan robustness and the ability of LDR and HDR treatments to precisely deliver the planned dose distribution. Real-time, adaptive treatment approaches can account for seed or source position uncertainties as treatment progresses, in contrast to approaches which incorporate uncertainties into the planning process. With precise knowledge of the actual dose delivered (in contrast to the planned dose distribution) we can develop reliable correlations of dose-to-normal tissue and toxicity. Similarly, this knowledge can be applied to biological modelling of tumour control probability to provide more reliable estimates of response to radiation in the presence of variable dose rates. Whilst long term clinical data supports the use of LDR in low risk patients, these data are based on the traditional approach to treatment of the entire prostate gland with high doses of radiation which is known to lead to a high incidence of acute urinary toxicity. Modern approaches suggest focal therapy may have a favourable affect on the therapeutic window. When comparing LDR and HDR monotherapy, clinical trials should consider current and future trends in treatment approaches to ensure outcomes represent treatment techniques that are likely to be commonplace in the future. SP-0348 Long-term results of LDR seed monotherapy in the treatment of prostate cancer S. Machtens 1 1 Marien-Krankenhaus Bergisch Gladbach, Urology and Paediatric Urology, Bergisch Gladbach, Germany Abstract text Permanent interstitial LDR-brachytherapy with seeds is an established guideline recommended treatment of patients with localized prostate cancer in the low- and low-intermediate risk category. Long-term tumour control data demonstrate comparable non-inferior results in comparison to radical prostatectomy (RP) and percutaneous radiation therapy (EBRT). 15-years results show tumor-dependent death rates between 5-10% in the low- and 10-25% in the low-intermediate risk category. Additional hormonal deprivation or the combination with EBRT did not show significant improval of tumour dependent death rates in this risk category. The side effect profil either in early and late toxicity is mild. The preservation of erectile function is in most retrospective studies superior to patients after RP or EBRT. Gastrointestinal toxicity (GI) is described to be less often than after EBRT. Genitouronary toxicity (GU) and irritative symptoms in particular are more often described than after EBRT or RP. Urinary incontinence is significantly less often reported than after RP. As prospective randomized trials in the direct comparison of the three treatment modalities are missing retrospective data are demonstrated in the presentation. SP-0349 Long-term results of HDR monotherapy in the treatment of prostate cancer Y. Yoshioka 1 1 Cancer Institu te Hospital of JFCR, Radiation Oncology, Tokyo, Japan Abstract text 9- to 7-fraction HDR monotherapy: HDR brachytherapy used as monotherapy for prostate cancer was initiated in Japan in 1995, which was reported in 2000 by Yoshioka et al. They delivered 8 or 9 fractions of 6 Gy each, in total 48 or 54 Gy over 5 days. After 10 years, they changed their dose fractionation into 45.5 Gy in 7 fractions over 4 days, with 6.5 Gy per each fraction. With a median 8- year follow-up and a total of 20 years of experience, they

SP-0345 For the motion seconder D. Sebag-Montefiore University of Leeds, Leeds, the United Kingdom

Abstract not received

SP-0346 Against the motion seconder Conventional chemoradiotherapy offers more opportunities for tailor made treatment than 5 x 5 Gy C. Rödel 1 1 Klinikum der Johann Wolfgang Goethe Univ, Academic Department of Radiation Oncology, Frankfurt, Germany Abstract text Current standard of neoadjuvant treatment for rectal cancer is either preoperative short-course radiotherapy (5 x 5 Gy) with immediate or delayed surgery or preoperative, conventionally fractionated radiotherapy with continuous infusion 5-FU or capecitabine (CRT), followed by total mesorectal excision surgery six to eight weeks thereafter. The monolithic approaches, however, to either apply the same schedule of preoperative 5-FU- based CRT or preoperative short-course RT to all patients with TNM stage II and III need to be questioned. Identifying and selecting patients for their most appropriate treatment alternatives based on tumor TN stage and MRI features (e.g., subgrouping of T3, mrCRM), location, molecular profiles, response, and to patients’ risk factors and preferences is mandatory. In this regard, CRT allows for tailor made treatment much better than 5 x 5 Gy as any combination with concurrent systemic treatment as well as RT dose adaption strategies (e.g., by use of SIB, contact RT boost) have been mainly established in combination with CRT. Tailor made alternatives include omission of radical surgery, e.g., for early, low-lying, CRT-responsive tumors that would otherwise require an abdominoperineal resection, but also omission of radiotherapy, e.g., for mid-/high lying tumors without threatened circumferential resection margins. Further treatment algorithms that need to be validated include neoadjuvant chemotherapy alone, or induction and consolidation chemotherapy before or after CRT, and the use of targeted agents for more advanced tumors. Thus, clinicopathological and molecular features as well as accurate imaging and response monitoring during treatment will take an integrative part in the multimodality management of rectal cancer patients. SP-0347 Differences in dosimetry, treatment planning, and equieffective dose A. Haworth 1 1 Institute of Medical Physics School of Physics A28, School of Physics, The University of Sydney, Australia Abstract text In appropriately selected prostate cancer patients treated with low dose rate (LDR) brachytherapy there is long term evidence of high clinical efficacy. High dose rate brachytherapy (HDR), when delivered as a single fraction provides an alternative treatment approach, though long term clinical efficacy data is lacking. As clinical trials develop to compare the outcomes of different treatment approaches, it is important to Symposium: Prostate brachytherapy: LDR seeds versus HDR monotherapy