Factors associated with local control in inflammatory breast cancer.

Abstract

126 Background: Inflammatory breast cancer (IBC) is an aggressive breast cancer variant, with 5-yr overall survival (OS) typically reported at 40-45%. We recently presented our results with once-daily radiotherapy (RT) as a component of trimodality therapy, with 5-yr OS of 64%. Herein we report patient and treatment factors associated with locoregional control (LRC). Methods: With permission of the IRB, review of medical records at the Mayo Clinic in Rochester, MN was performed to identify patients treated with RT for IBC from 2000-2010. Patients with non-metastatic, clinically diagnosed IBC were included. OS, LRC and distant metastasis-free survival (DMFS) were assessed using the Kaplan-Meier method. First recurrence in the chest wall or regional lymph nodes was defined as a locoregional recurrence (LRR). Results: 52 women were included in the analysis. Median age at diagnosis was 54 years (range 23-83). Median follow-up for the population was 3.6 years (range 0.7 – 11.9). All patients were treated with adjuvant RT to the chest wall and draining nodal basins in once-daily fractions of 1.8-2.25 Gy (median 2 Gy), to a median of 50 Gy (range 46-60 Gy). Actuarial 5-yr LRC was 85%. LRR was associated with poorer DMFS and OS (p < 0.01). Factors significantly associated with improved LRC included lack of extracapsular extension (ECE) and use of adjuvant chemotherapy (p < 0.05). Factors associated with a trend towards LRC included use of bolus, absence of boost, node negativity at time of surgery and pathologic complete response (pCR). Daily bolus was employed in 90% of patients and was most commonly (68%) 1 cm in thickness. There was a trend towards improved 5-yr LRC when bolus ≥ 1 cm was employed daily (93% v. 67%, p = 0.06). Patients who received a boost to the mastectomy scar (62% of the population, median of 10 Gy, range 10-16 Gy) had poorer LRC (78% v. 100%, p = 0.08), but superior 5-yr DMFS (78% v. 34%, p = 0.035) and OS (77% v. 34%, p = 0.04). Conclusions: LRC is associated with improved OS in IBC. Lack of ECE and use of adjuvant chemotherapy are associated with improved LRC in women with IBC. Node negativity, pCR and use of daily bolus ≥1 cm in thickness are associated with a trend towards improved LRC. The impact of boost requires further analysis.