ESTRO 36 Abstract Book

S339 ESTRO 36 _______________________________________________________________________________________________

primary treatment for most of patients. Of those older patients, 37 patients were treated with radiotherapy alone, 17 patients with radiotherapy combined with chemotherapy, 3 patients with chemotherapy alone and one patient with anti-inflammation therapy. Survivals were estimated using the Kaplan-Meier method. Propensity Score Matching (PSM) was applied for 544 patients with ratio 1:2, and covariates included sex, B symptoms, lactate dehydrogenase (LDH), ECOG Performance Status, primary location, Ann Arbor stage and primary tumor invasion. 116 patients with age≤60 were eventually matched by PSM. Results Median follow-up time was 39 months (range, 2-174 months) for 58 older patients and 30 months (range, 1-435 months) for 116 matched patients. Well-balanced pairs of different covariates were established by PSM (p<0.05). After matching, overall survival (OS), cancer-specific survival (CSS), progressive free survival (PFS) and local- reginal control (LRC) were no significant difference between patients with age>60 and with age≤60. 5-year OS were 61.4% and 68.9% ( p =0.326), 5-year CSS were 69.1% and 71.4% (p=0.902), 5-year PFS were 61.3% and 63.9% (p=0.594), and 5-year LRC were 87.2% and 88.1% (p=0.628), respectively. Conclusion Older patients with early stage UADT-NKTCL have good prognosis after radiotherapy is the primary treatment. Age>60 is not unfavorable prognostic factor for early stage UADT-NKTCL. The patients with age>60 have similar survivals with the patients with age≤60. PO-0649 Locoregional Treatment of the Primary Tumor Shows Survival Benefit in De Novo Stage IV Breast Cancer S.H. Choi 1 , W.J. Rhee 1 , J.W. Kim 1 , C.O. Suh 1 , K.C. Keum 1 , Y.B. Kim 1 , I.J. Lee 1 1 Yonsei University, Radiation Oncology, SEOUL, Korea Republic of Purpose or Objective Although systemic therapy is a mainstay of treatment for metastatic breast cancer, the role of locoregional treatment (LRT) of the primary tumor for an overall survival advantage is still unclear. The aim of this study was to assess the clinical outcomes of patients with de novo stage IV breast cancer after undergoing LRT of the primary site. Material and Methods From January 2006 to November 2013, a total of 245 patients diagnosed with de novo stage IV breast cancer at Yonsei University Health System were included. Among them, LRT of primary tumor (+ systemic therapy) was performed in 86 patients (35%) (Surgery only : n = 28, surgery + radiotherapy (RT) : n = 47, RT only : n = 11). The remaining 155 patients (63%) received systemic therapies (chemotherapy and/or hormone therapy), while 4 patients (2%) received no treatment. For surgery type, 87% (n = 66) received mastectomy, and 12% (n = 9) received breast- conserving surgery (BCS). Local recurrence-free survival (LRFS) and overall survival (OS) were investigated, and propensity score matching method was used to balance The median follow-up duration was 40 months (Range, 13 days to 124 months). The 5-year LRFS and OS rates were 27% and 50%, respectively. Total of 188 patients (77%) experienced recurrence, while local recurrence rate was 45% (LRT group 12% vs. no LRT group 47%, p <0.001) and systemic recurrence rate was 95% (LRT group 69% vs. no LRT group 76%, p=0.248). Advanced T stage (T4), liver or groups. Results Poster: Clinical track: Breast

brain metastasis, ≥5 metastatic sites, no hormone therapy, and LRT(-) were considered significant adverse factors for LRFS, while T4 stage, no hormone therapy, and LRT(-) were considered significant for OS. LRT group demonstrated favorable outcome (5-year LRFS: 55% and 5- year OS: 71%), especially when surgery was performed. Even after matching the baseline characteristics, survival rates were still significantly higher in LRT group than no LRT group (5-year LRFS 55% vs. 22%, p<0.001, 5-year OS 71% vs. 43%, p<0.001). Furthermore, LRT (especially surgery) was an important good prognostic factor in patients with