91 LONG TERM OUTCOMES AND RECURRENCE PATTERN FOLLOWING ACCELERATED PARTIAL BREAST IRRADIATION USING MAMMOSITE

Abstract

Purpose/Objective: To evaluate: 1. The incidence of locoregional recurrence in early breast cancer treated by APBI using the MammoSite device in patients grouped according to ASTRO consensus panel 'suitable 'and 'cautionary' category. 2. The recurrence pattern in patients with 'triple negative tumor' (TN) (negative Estrogen, Progesterone receptor and Human Epidermal Growth factor (HER-2)) and the association and outcomes of African American, Hispanic ethnicity and ER negative tumor. Materials and Methods: Between June 2003 and December 2009, 83 post-menopausal patients:76 invasive ductal carcinoma (IDC), 7 ductal carcinoma in situ (DCIS), with diagnosis of early stage breast cancer and node negative status met our inclusion criteria for APBI using the single lumen MammoSite balloon catheter. Following a CT scan based 3D plan a dose of 3400cGy was prescribed in 10 fractions at distance of 1 cm from surface of balloon delivered twice daily, 6 hours apart using the high dose rate system. Patients were categorized as 4 groups: ASTRO consensus 'suitable', 'cautionary', TN and TN plus Her-2 positive ('High Risk'). Data on treatment outcome with for ipsilateral breast tumor recurrence (IBTR), tumor bed area failure (TBF), elsewhere failure in the same breast (EF), ipsilateral axilla failure (IAF) was analyzed. Results: There were 42/83 (51%) patients in the 'suitable' and 41/83 (49%) in the 'cautionary' group. TN was 11% (8/76) and 'High risk' was 24% (18/76) of invasive cancer patients. Mean age of invasive cancer patients was 72 years. Median follow-up for all 83 patients was 61 months; 'cautionary' group= 61 months; triple negative= 59; 'suitable' group=61 and 'High risk'= 59. Adjuvant chemotherapy was given in 18% (14/76) and hormones in 85% ER+ IDC patients. The locoregional control was 98.6%. IBTR that was EF occurred in 2/83 (2.4%) patients; one from the 'cautionary' group (ER-, HER2+) and another from the 'suitable' group (ER+, HER2-). IAF was seen in the first patient. There was a significant association between tumor grade and ethnicity with grade 3 tumors seen more in Hispanic and black women as compared to others (31% vs. 8%; p=0.03) in the invasive group. There was a higher proportion of ER-negative tumors seen among African American and Hispanics compared to other ethnicities (56.25% vs. 8.33%; p<.0001)