ESTRO 2020 Abstract Book

S201 ESTRO 2020

extracranial on choline PET-CT and a serum testosterone levels > 50 ng/ml. Patients were randomly assigned (1:1) to either surveillance or MDT of all detected lesions. Randomisation was balanced dynamically on two factors: PSA doubling time (≤3 vs. > 3 months) and nodal vs non- nodal metastases. The primary endpoint was androgen deprivation therapy (ADT)-free survival. Castrate resistant prostate cancer-free survival (CRPC) was a secondary endpoint. Tests were performed two-sided; p values less than 0.20 were deemed significant. Results The 5-year ADT-free survival was 8% for the surveillance group and 34% for the MDT group (Figure 1, hazard ratio 0.57 [80% CI: 0.38-0.84], log-rank p = 0.06). There was no significant difference in effect for the different stratification factors (interaction test). The 5-year CRPC- free survival was 53% for the surveillance group and 76% for the MDT group (hazard ratio 0.62 [80% CI: 0.35−1.09]; log−rank p = 0.27). At a median follow for survival of 5.3 years (IQR 4.3-6.3), the 5-year overall survival was 85%, with 6 out of 14 deaths attributed to prostate cancer. Conclusion The updated STOMP trial outcomes confirm the earlier reported significant difference in ADT free survival in favor of the MDT group compared to surveillance. Prostate- cancer related mortality is low within the first 5 years of diagnosis of oligorecurrent prostate cancer. OC-0371 Hypo- vs normofractionated radiation of early breast cancer in the randomized DBCG HYPO trial B. Vrou Offersen 1 , H.M. Nielsen 2 , E.H. Jacobsen 3 , M.H. Nielsen 4 , M. Krause 5 , L. Stenbygaard 6 , I. Mjaaland 7 , A. Schreiber 8 , U. Kasti 9 , M. Jensen 10 , J. Alsner 1 , J. Overgaard 1 1 Aarhus University Hospital, Experimental Clinical Oncology, Aarhus N, Denmark ; 2 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark ; 3 Lillebaelt Hospital, Department of Oncology, Vejle, Denmark ; 4 Odense University Hospital, Department of Oncology, Odense, Denmark ; 5 University Clinic Carl Gustav Carus, Clinic for Radiotherapy and Oncology, Dresden, Germany ; 6 Aalborg University Hospital, Department of Oncology, Aalborg, Denmark ; 7 Stavanger University Hospital, Department of Oncology, Stavanger, Norway ; 8 Academic Teaching Hospital Dresden- Friedrichstadt, Department of Oncology, Dresden, Germany ; 9 Kristiansand hospital, Department of Oncology, Kristiansand, Norway ; 10 Rigshospitalet, Danish Breast Cancer Group, Copenhagen, Denmark Purpose or Objective Based on poor results using hypofractionated adjuvant radiotherapy (RT) of early breast cancer (BC) 50 Gy/25 fr. has been Danish Breast Cancer Group (DBCG) standard since 1982. Results from the UK and Canada stimulated a renewed interest in hypofractionation, and the non- inferiority DBCG HYPO trial was initiated. The hypothesis was that 40 Gy/15 fr (2.67 Gy/fr, 3 weeks) does not result in more grade 2-3 breast induration than 50 Gy/25 fr (2.0 Gy/fr, 5 weeks) 3 years post RT. Material and Methods From 2009-2014, 1882 patients >40 years operated with breast conservation for early pT1-2 pN0-1(mic) BC (n=1631) or DCIS (n=251) were enrolled irrespective of breast size, systemic therapy and boost, and randomized 50 Gy/25 fr vs. 40Gy/15 fr. Strata were institution, breast size (≤ 600 ml vs. > 600 ml), systemic therapy and boost. The primary endpoint was grade 2-3 induration 3 years post RT, secondary endpoints were other normal tissue

responses, genetic risk profile for RT-induced fibrosis and recurrences. ClinicalTrial NCT00909818. Results 949 pts (50.4%) were assigned to the 50 Gy group and 933 (49.6%) to the 40 Gy group. Median age was 59 years (range 39-83). Median follow up was 8 years. The analysis was by intention to treat. Results are actuarial 3- and 5-year rates using morbidity in 1800 pts 1 yr post RT as baseline. 1464 pts (78%) and 990 pts (53%) had 3 and 5 year scores of morbidity. Grade 2-3 induration at 3 and 5 years was seen in the 50 Gy group in 14% and 18% of the pts, and in the 40 Gy group in 10% and 14% of the pts, representing a HR (40 Gy vs 50 Gy) 0.75 (0.59-0.96). 860 pts (48%) had small breasts and 940 pts (52%) had large breasts. Comparing the risk of grade 2-3 induration in small vs large breasts the HR was 1.65 (1.29-2.12). In total 653 pts (36%) were treated with chemotherapy (CT), and CT did not increase the risk of grade 2-3 induration, HR (CT vs no CT) 0.99 (0.77-1.28). Sequential boost (10-16 Gy/5-8 fr) was delivered to 421 pts (23%) and comparing boost vs no boost revealed a HR 0.85 (0.63-1.14). Current smokers comprised 19% (334 patients) of the cohort, and for smokers vs no/previous smokers the HR was 1.80 (1.38-2.36). Multivariate analysis using grade 2-3 induration as endpoint and including hypofractionation, breast size, chemotherapy, smoking and boost identified hypofractionation (HR 0.76 (0.59- 0.97)), large breast size (HR 1.69 (1.32-2.18)), and current smoking (HR 1.87 (1.43-2.44)) as independent risk factors. In the 50 Gy / 40 Gy group loco-regional recurrence was reported in 17 pts / 17 pts at 8 years follow up. Updated results will be provided at the conference. Conclusion Moderately hypofractionated whole breast irradiation in early node-negative BC or DCIS causes less grade 2-3 induration compared to normofractionated therapy. Large breast size and being current smoker are independent risk factors for developing induration. The 8 yr loco-regional recurrence risk is very low. OC-0372 Phase 2 RCT comparing conventional radiotherapy with SBRT in patients with bone metastases B. Pielkenrood 1 , J. Van der Velden 1 , Y. Van der Linden 2 , M. Bartels 1 , N. Kasperts 1 , J. Verhoeff 1 , W. Eppinga 1 , R. Gal 1 , J. Verlaan 3 , H. Verkooijen 4 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands ; 2 Leiden University Medical Center, Radiotherapy, Leiden, The Netherlands ; 3 UMC Utrecht, Orthopedic Surgery, Utrecht, The Netherlands ; 4 UMC Utrecht, Imaging & Oncology, Utrecht, The Netherlands Purpose or Objective Studies looking at the impact of Stereotactic Body Radiation Therapy(SBRT) on pain response in patients with painful bone metastases show inconsistent results. The aim of the VERTICAL trial was to investigate the difference in pain response between patients treated with conventional radiotherapy(cRT) versus SBRT. We used the Trials within Cohorts design, which allowed us to estimate the acceptability of the intervention to patients. Material and Methods This single center, non-blinded, phase 2 randomized controlled trial was embedded within the PRESENT cohort. PRESENT includes patients referred for radiation therapy for bone metastases to the UMC Utrecht, the Netherlands. At cohort entry, patients may provide broad consent for future randomization. Cohort participants with painful bone metastases who were eligible for the VERTICAL trial were randomized. Patients randomized to the intervention