PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s):Previous retrospective studies showed that dose escalation of post-mastectomy radiation therapy (PMRT) improved locoregional control for IBC patients. However, modern multi-modality therapy for IBC has broadly improved outcomes, and most previous retrospective studies included patients not treated with anthracycline/taxane based chemotherapy. The purpose of this study was to determine locoregional recurrence rates following modern multi-modality treatment including PMRT for non-metastatic IBC. Secondary objectives were to identify predictors of locoregional relapse which could be used to identify candidates for dose-escalated radiotherapy, and to assess the impact of hypofractionation.
Materials/Methods:All patients diagnosed with non-metastatic IBC (T4d, M0 at diagnosis) at four institutions in a large Canadian province between 2000 and 2011 were identified from the provincial cancer registry. Patients treated with triple modality therapy (chemotherapy, surgery, and PMRT) were included in the analysis. Actuarial 5-year outcomes were calculated, and survival distributions were compared with the log-rank test. α = 0.05.
Results:168 patients met eligibility criteria, all of whom received anthracycline and/or taxane based chemotherapy. Median follow-up was 58 months. At 5 years, overall survival was 55%, locoregional control was 70%, and distant metastasis–free survival was 49%. 80 patients received hypofractionated RT (HypoF; 40-45 Gy in 16-20 fractions), 61 patients received conventionally fractionated RT (CF, 50 Gy in 25 fractions), and 27 patients received other regimens. Outcomes were not statistically different between HypoF and CF regimens, including 5-year overall survival (51% vs 60%, p = 0.896), 5-year locoregional control (74% vs 67%, p = 0.108), and 5-year distant-metastasis free survival (48% vs 52%, p = 0.649) for HypoF vs CF, respectively. Among the 81 patients who recurred, first sites of failure were locoregional (47%) or distant (46%), with 7% being simultaneous. Patients with triple-negative (TN) disease more frequently first failed locoregionally (77% vs 43% in all other patients, p = 0.016), and 5-year locoregional control was significantly inferior for TN patients (53% vs 73% in others, p = 0.015). In contrast, patients with hormone receptor positive, HER2-negative disease were less likely to first fail locoregionally (35% vs 58% in other patients, p = 0.067).
Conclusion:Patients with IBC who completed triple-modality therapy in the past decade still had poor local control and frequently first failed locoregionally, but outcomes were independent of fractionation among the regimens used. Escalation of PMRT dose may still be of benefit in this high-risk population in the era of modern chemotherapy, especially for TN patients.
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