Abstract Book

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ESTRO 37

Results A retrospective consecutive cohort of 58 MBC patients was analysed. Median follow-up for the entire study population was 38 months. Twenty one out of 58 patients (36.2%) received adjuvant RT. Overall, patients receiving postoperative RT presented with more high-risk features. Patients receiving postoperative RT had significantly higher UICC-stage (UICC III in 50% vs 9.7%, p=0.018) and positive lymph nodes when compared to surgery alone (pN+ in 65% vs 34.4%, p=0.046). Accordingly, there was a higher ratio of patients receiving an axillary lymph node dissection in the RT group (52.4% vs 28.6%). Mastectomy was performed in 31/37 (86.1%) in the surgery only group as compared to 14/21 (66.7%) of patients receiving postoperative RT. Additionally, patients undergoing RT also received additional endocrine therapy significantly more often (78.9% vs 39.3%, p=0.016). Outcome was not significantly different between the groups (5-year local recurrence free survival: 89.8% vs 80.0%, p=0.471 and 5- year overall survival 82.8 % vs 77.8%, p=0.819). Conclusion To date, few data are available on MBC. The present observational study evaluated the pattern of care of BMC patients treated in clinical practice. Due to its rarity, randomized clinical trials are unlikely and MBC remains a neglected entity. Nevertheless, RT still remains a crucial component of the multidisciplinary treatment strategy in MBC. EP-1337 Exclusive IORT in breast cancer: outcome analysis of a pilot trial at two different single doses L. Belgioia 1 , M. Guenzi 2 , E. Bonzano 2 , G. Blandino 2 , F. Cavagnetto 3 , S. Garelli 3 , D. Friedman 4 , R. Corvò 5 1 University of Genoa, Department of Health Science DISSAL, Genoa, Italy 2 Ospedale Policlinico San Martino Genova, Radiation Oncology, Genoa, Italy 3 Ospedale Policlinico San Martino Genova, Medical Physics, Genoa, Italy 4 University of Genoa-Ospedale Policlinico San Martino Genova, Surgery, Genoa, Italy 5 University of Genoa-Ospedale Policlinico San Martino Genova, Radiation Oncology, Genoa, Italy Purpose or Objective To evaluate outcomes to exclusive intra-operative radiotherapy (IORT) with different single doses for conservative breast cancer treatment. Material and Methods From October 2009 to December 2011, 178 patients candidates for IORT were included in a monoinstitutional pilot study approved by ethic committee (NCT01276938). Eligibility criteria included: patients aged 45 to 85 years with unifocal and non lobular invasive carcinoma (LIC), a maximum tumor diameter of 2.5 cm, negative margin, intraductal component <25% and no previous history of cancer. Prescription dose depends on tumor size evaluated with frozen section examination; if < 1 cm total dose was 18 Gy, if > 1cm (up to 2.5 cm) the pts received 21 Gy. Using α/β ratio for breast tumor of 4 Gy, 21 Gy in 1 fraction would be biologically equivalent to 70 Gy while 18 Gy was equivalent to 60 Gy. Full-dose intraoperative radiotherapy with electrons was delivered using a LIAC (Sordina, Padova, Italy), a mobile linear accelerator delivering an electron beam with energies ranging from 4 to 10 Mev. Primary endpoint was local relapse free survival (LRFS), secondary endpoints were disease free survival (DFS) and overall survival (OS). Results 169 (95%) patients were analyzed, 9 were excluded as lost at follow up. The median follow-up is 72 months (9- 96 months). Median age was 67 years (range 45-85). 71 (42%) and 98 (58%) patients received 18 Gy and 21 Gy, respectively. 7 patients presented local relapse (2 and 5 pts in 18 Gy and 21 Gy arm, respectively) and 1 patients

160, 37%) between 2008 and 2011 were reviewed. Primary endpoint of the analysis was the incidence of acute and late toxicity retrospectively evaluated with the NCI-CTCAE v4.0 criteria. We also calculated and reported the 5-year locoregional-free survival (LRR-FS), disease- free survival (DFS) and overall survival (OS). Results Treatment was globally well-tolerated. Grade 3 (or more) acute toxicity was found in 4.4% of the HRT cohort and 3.1% of the HLRT one (p=0.79), usually as dermatitis. HLRT patients presented more frequently G1-2 dysphagia (30.6% vs 0.4%, p<0.001) and/or G1-2 lymphedema (5.6% vs 0.4%, p=0.002). At multivariate analysis, tabagism was the only independent factor statistically influencing the risk of acute toxicity (p=0.047). Concerning late toxicity, HLRT patients presented more frequently G1-2 lymphedema (6.2% vs 0.7%, p=0.003). Noteworthy, there were significantly more patients presenting a postoperative lymphedema (any grade) in the HLRT than HRT arm (5% vs 0.4% p=0.005). When we excluded these patients with any grade of lymphedema before RT (n = 9) and those where this information was lacking in the clinical chart (n =5), only 2 patients presented a G2 lymphedema (both treated with HLRT) and 8 a G1 lymphedema (5 treated with HLRT and 3 with HRT). This difference in the incidence of G1-2 lymphedema in our 2 cohorts was significantly different (two-tailed Fisher Exact p-value 0.041). Median follow-up was 61.7 months. Five-year OS was 96.4% and 92.6% in the HRT and in the HLRT group, respectively (p=0.027). Five-year LRR-FS was 96.3% and 92% in the HRT and in the HLRT population, respectively (p=0.004). Five-year DFS was 92.2% and 83.4% in the HRT and in the HLRT population, respectively (p=0.004). Conclusion HLRT is safe and the clinical outcomes of our patients are comparable to the results of available randomized trials on hypofractionation for breast cancer. Further, prospective randomized trials comparing standard fractionated loco-regional RT and HLRT are warranted to confirm our data and consider HLRT as a standard of care. EP-1336 The role of adjuvant radiotherapy in male breast cancer patients in clinical practice P. Rogowski 1 , M. Pazos 1 , S. Schönecker 1 , D. Reitz 1 , M. Braun 2 , N. Harbeck 3 , J. Engel 4 , C. Belka 1 , S. Corradini 1 1 University Hospital- LMU Munich, Department of Radiation Oncology, Munich, Germany 2 Red Cross Hospital, Department of Obstetrics and Gynecology- Breast Centre, Munich, Germany 3 University Hospital- LMU Munich, Department of Obstetrics and Gynecology- Breast Centre, Munich, Germany 4 LMU Munich, Munich Cancer Registry MCR of the Munich Tumour Centre TZM at the Institute of Medical Information Processing- Biometry and Epidemiology IBE, Munich, Germany Purpose or Objective Male breast cancer (MBC) is a rare disease. To date, no consensus has been reached in regards to the most appropriate curative treatment strategy. The objective of the present observational study was to identify patient and tumour characteristics and to assess the role of radiotherapy (RT) in the MBC setting in clinical practice. Material and Methods Between 1998 and 2014, patients with MBC and treated at the breast centre of LMU and Redcross hospital of Munich were retrospectively evaluated. Patients were sub-stratified based on the addition of adjuvant RT. Data on overall survival, disease-free survival, local recurrence-free survival and distant metastasis-free survival were estimated with the Kaplan-Meier method and compared by log-rank testing.