V. Gunaseelan

Higher Chest Wall Dose Results in Improved Locoregional Outcome in Patients Receiving Postmastectomy Radiation

PURPOSE Randomized trials demonstrating decreased locoregional recurrence (LRR) and improved overall survival (OS) in women receiving postmastectomy radiation therapy (PMRT) used up to 50 Gy to the chest wall (CW), but in practice, many centers boost the CW dose to ≥60 Gy, despite lack of data supporting this approach. We evaluated the relationship between CW dose and clinical outcome. METHODS AND MATERIALS We retrospectively reviewed medical records of 582 consecutively treated patients who received PMRT between January 1999 and December 2009. We collected data on patient, disease, treatment characteristics, and outcomes of LRR, progression-free survival (PFS) and OS. RESULTS Median follow-up from the date of diagnosis was 44.7 months. The cumulative 5-year incidence of LRR as first site of failure was 6.2%. CW dose for 7% (43 patients) was ≤50.4 Gy (range, 41.4-50.4 Gy) and 93% received >50.4 Gy (range, 52.4-74.4 Gy). A CW dose of >50.4 Gy vs. ≤50.4 Gy was associated with lower incidence of LRR, a 60-month rate of 5.7% (95% confidence interval [CI], 3.7-8.2) vs. 12.7% (95% CI, 4.5-25.3; p = 0.054). Multivariate hazard ratio (HR) for LRR controlling for race, receptor status, and stage was 2.62 (95% CI, 1.02-7.13; p = 0.042). All LRR in the low-dose group occurred in patients receiving 50 to 50.4 Gy. Lower CW dose was associated with worse PFS (multivariate HR, 2.73; 95% CI, 1.64-4.56; p < 0.001) and OS (multivariate HR, 3.88; 95% CI, 2.16-6.99; p < 0.001). CONCLUSIONS The addition of a CW boost above 50.4 Gy resulted in improved locoregional control and survival in this cohort patients treated with PMRT for stage II-III breast cancer. The addition of a CW boost to standard-dose PMRT is likely to benefit selected high-risk patients. The optimal technique, target volume, and patient selection criteria are unknown. The use of a CW boost should be studied prospectively, as has been done in the setting of breast conservation.