Local failure and acute radiodermatological toxicity in patients undergoing radiation therapy with and without postmastectomy chest wall bolus: Is bolus ever necessary?

PURPOSE: Postmastectomy chest wall radiation therapy has historically used bolus to increase dose at the skin surface. Despite the theoretical benefits of bolus, the clinical implications of locoregional tumor control, cosmesis, and the incidence of radiodermatitis are less well characterized. We hypothesized that treatment in the presence or absence of bolus results in equivalent chest wall recurrence rates, but its presence results in more severe acute dermatologic toxicity.

METHODS AND MATERIALS: Locally advanced breast cancer patients undergoing chest wall radiation therapy were retrospectively reviewed from 2005 to 2015 (n = 106; 53 with bolus, 53 without). Outcomes including local failure, acute skin toxicity, and treatment interruptions were recorded. Median age was 59 years (range, 28-91) and median follow-up was 34 months. Histology was invasive ductal carcinoma (73%), invasive lobular carcinoma (20%), inflammatory (6%), and neuroendocrine (1%). Fifty-nine percent were T3/T4 primary tumors and 29.2% had clinical/pathologic skin involvement. Node-positive patients accounted for 80.2%. Chemotherapy was administered in 84.0%. All patients had 3-dimensional conformal radiation therapy and received a median dose of 61Gy (range, 50-63 Gy).

RESULTS: Local failure was 6.6% (n = 7) overall, with 4 failures in the bolus group and 3 in the no bolus group. No pathological factors were associated with local failure. Acute grade 2 and 3 skin toxicities (37 vs 22) and treatment interruptions (20 vs 3) were more common in the bolus group (P < .05). Mean treatment interruption (14.5 vs 5 days) was longer for patients receiving bolus. Patients undergoing treatment interruption were more likely to fail locally than patients not requiring a treatment interruption (17.4% vs 3.6%, P = .0322).

CONCLUSIONS: Bolus omission in adjuvant chest wall radiation therapy may be a reasonable approach to avoid acute skin toxicity and treatment interruptions while preserving local control; however, further study will be needed to reach a definitive conclusion.