Abstract Book

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ESTRO 37

Stavanger, Norway 8 academic Teaching Hospital Dresden-Friedrichstadt, Dept Oncology, Dresden, Germany 9 kristiansand Hospital, Dept 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, 1883 patients >40 years operated with breast conservation for early pT1-2 pN0-1(mic) BC (n=1617) 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 942 pts (50.4%) were assigned to the 50 Gy group and 926 (49.6%) to the 40 Gy group. Median age was 59 years (range 39-83). Median follow up was 5 years. The analysis was by intention to treat. Results are actuarial 3- and 5- year rates using morbidity in 1801 pts 1 yr post RT as baseline. 1641 pts (87%) and 886 pts (47%) 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 16% of the pts, and in the 40 Gy group in 12% and 13% of the pts, representing a HR (40 Gy vs 50 Gy) 0.78 (0.61-1.01). 859 pts (48%) had small breasts and 942 pts (52%) had large breasts. Comparing the risk of grade 2-3 induration in small vs large breasts the HR was 1.48 (1.14-1.92). 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) 0.96 (0.74-1.25). Sequential boost (10- 16 Gy/5-8 fr) was delivered to 423 pts (23%) and comparing boost vs no boost revealed a HR 0.89 (0.66- 1.21). Multivariate analysis using grade 2-3 induration as endpoint and including hypofractionation, breast size, chemotherapy and boost identified large breast size as the only independent risk factor (HR 1.49, (1.15-1.93)). In the 50 Gy / 40 Gy group loco-regional recurrence was reported in 11 pts / 10 pts, distant failure 17 pts / 14 pts, new contralateral cancer or DCIS 12 pts / 12 pts. Updated results will be provided at the ESTRO Moderately hypofractionated whole breast irradiation in early node-negative BC or DCIS does not result in more grade 2-3 induration compared to normofractionated therapy. Large breast size is an independent risk factor for developing induration. The 5 yr loco-regional recurrence risk is very low. OC-0597 Tumor-infiltrating lymphocytes predicts improved overall survival after post-mastectomy radiotherapy T. Tramm 1 , H. Vinter 2 , J. Alsner 3 , J. Overgaard 3 1 aarhus university hospital, dept. Of pathology, aarhus n, denmark 2 viborg regional hospital, dept. Of pathology, viborg, denmark 3 aarhus university hospital, dept. Of experimental clinical oncology, aarhus c, denmark conference. Conclusion

sectional analyses at specific time-points and survival analysis. Due to multiple testing a significance level of 0.005 was used. A lymphatic sub-study is ongoing. Results From November 2011 to June 2014, 4096 consenting patients were recruited (1361 40Gy, 1367 27Gy, 1368 26Gy). Median follow-up is 48 months (IQR 37-50), with 98% of year 3 visit forms returned. Levels of marked NTEs at 2 or 3 years were very low (Table). Clinician assessments of individual NTEs at 3 years and patient assessments at 2 years were similar between schedules. Prevalence of change in photographic breast appearance at 2 years was statistically significantly higher for 27Gy compared with 40Gy, but similar for 26Gy with 40Gy. The composite endpoint of any clinician-assessed NTE in the breast showed statistically significantly higher levels at 3 years for 27Gy compared with 40Gy (excess of moderate/marked effects +4.4%, 95%CI 1.6-7.2); 26Gy was similar to 40Gy (+1.4%, -1.2 – 4.0). Cumulative incidence rates of any clinician-assessed moderate/marked NTE in the breast up to 3 years were 40Gy: 20.8% (95%CI 18.6-23.2), 27Gy: 28.8% (26.4-31.4), 26Gy: 21.8% (19.6-24.2).

Conclusion Levels of marked NTEs were low for all schedules. Late effects after 26Gy in 5 fractions over 1 week appear to be similar to 40Gy in 15 fractions over 3 weeks. OC-0596 Hypo- vs normofractionated radiation of early breast cancer in the randomized DBCG HYPO trial B. 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.M. Kasti 9 , M.B. Jensen 10 , J. Alsner 1 , J. Overgaard 1 1 aarhus University Hospital, Dept Experimental Clinical Oncology, Aarhus C, Denmark 2 aarhus University Hospital, Dept Oncology, Aarhus C, Denmark 3 lillebaelt Hospital, Dept Oncology, Vejle, Denmark 4 odense University Hospital, Dept Oncology, Odense, Denmark 5 university Clinic Carl Gustav Carus- Technical University Dresden, Clinic For Radiotherapy And Oncology, Dresden, Germany 6 aalborg University Hospital, Dept Oncology, Aalborg, Denmark 7 stavanger University Hospital, Dept Oncology,