A feasibility study of 2-mm bolus for postmastectomy radiation therapy.

PURPOSE: The purpose of this study was to prospectively evaluate the use of daily 2-mm bolus in patients undergoing postmastectomy radiation without reconstruction using optically stimulated luminescence dosimetry and weekly assessment of skin toxicity.

METHODS AND MATERIALS: We prospectively collected data from the first 49 women treated with a daily 2-mm Superflab bolus during their postmastectomy radiation therapy from 2013 to 2016 at The University of Chicago Comprehensive Cancer Center at Silver Cross. Within the first 3 days of starting radiation therapy, we measured the surface dose in vivo at 5 anatomical locations under the 2-mm bolus on the chest wall. We assessed weekly the acute skin toxicity during radiation using the National Cancer Institute Common Toxicity Criteria. Patients with reconstruction before radiation therapy were excluded.

RESULTS: Forty-nine women with a mean age of 54.3 years were treated with daily 2-mm bolus to the chest wall following mastectomy. Median follow-up was 32.7 weeks. The mean percentages of prescribed dose (standard deviation) for the median, central, lateral, superior, and inferior optically stimulated luminescence dosimeters were 100.1% (5.6%), 108.1% (6.7%), 98.1% (6.5%), 102.6% (8.9%), and 106.3% (6.6%), respectively. The majority (71.4%) of women experienced a maximum acute National Cancer Institute Common Toxicity Criteria skin toxicity score of 2, with only 12.2% experiencing a score of 3. There were no grade 4 toxicities. There were no local recurrences during our follow-up period.

CONCLUSIONS: A daily 2-mm bolus is a feasible regimen for chest wall bolus during postmastectomy radiation therapy with acceptable dose buildup and skin toxicity.