Triple-Negative Breast Cancer (Tnbc) Outcomes With Partial Breast Irradiation And Concurrent Chemotherapy (Pbi-Cc) Compared With Whole Breast Irradiation And Sequential Chemotherapy (Wbi-Sc).

115 Background: TNBC (ER/PR/HER2-negative) is associated with worse locoregional recurrence (LRR), disease-free survival (DFS), and overall survival (OS) than non-TNBC. MSKCC/Harvard recently reported a 5-yr local recurrence rate of 33% in TNBC patients treated with PBI (Pashtan et. al. ASTRO 2010). Having completed two prospective trials of PBI-CC, one previously reported (Zellars et al. JCO 2009), we reviewed the outcomes of TNBC patients treated with PBI-CC and compared them to those treated with WBI-SC. Methods: TNBC patients treated on 2 phase I/II PBI-CC protocols were compared to a cohort of TNBC patients treated at our institution with WBI-SC with respect to OS, DFS, LRR and in-breast tumor recurrence (IBTR). KM rates of local and distant recurrence, log-rank test of statistical significance are presented. Results: Between 2004 and 2009, 16 patients were treated with PBI-CC and 32 with WBI-SC. PBI-CC was 40.5 Gy (2.7 Gy x 15 QD) to the lumpectomy bed only with cycle 1 of ddAC (60/600 mg/m2 every 14 days with growth factor support x 4 cycles). WBI-SC patients received a med. dose (+ boost) of 60.7 Gy, (42.5 – 66), 5/32 had nodal irradiation. 28/32 recieved AC, and 4/32 C, Docetaxel. Med. follow-up is 38.4 mo (9.2–65.5) and 40.5 mo (5.6–77.8), respectively. There is no statistically significant difference between groups with respect to T/N stage, median age, and menopausal status. No patients died. All 6 recurrences (1 nodal, 4 IBTR, 1 distant) were in the WBI-SC group. Med. time to recurrence was 14.4 months (0.8–38.6). DFS at 3 yr/5 yr were 100% vs. 84.4% (p=0.10) and 100% vs. 81.3%. (p=0.07) in the PBI-CC and WBI-SC groups respectively. There is a trend towards decreased LRR (0% vs. 15.6%, p=0.12) and IBTR (0% vs. 12.5% , p=0.16), in favor of PBI-CC. Conclusions: Our results differ from earlier reports of a high rate of LRR in TNBC patients treated with PBI. This may be due to our use of concurrent chemotherapy with PBI or to undefined factors in our series of WBI-SC. Our data suggest improved DFS, LRR, and IBTR with PBI-CC when compared to retrospectively reviewed contemporary TNBC patients treated WBI-SC and should be externally confirmed.