Dosimetric effect of silicone-based gel on skin surface during volumetric modulated arc therapy for breast cancer

This study aims to quantify and compare the dosimetric effects of varying thicknesses of StrataXRT, a silicone-based gel, and other topical agents on the skin surface during volumetric modulated arc therapy (VMAT) for breast cancer.

A VMAT plan was created for breast cancer treatment using a female RANDO phantom with a prescription dose of 50 Gy in 25 fractions. The planning target volume (PTV) encompassed the left breast and the regional lymph nodes. Irradiation was performed using a 6 MV photon beam. Three topical agents (StrataXRT, Hirudoid Soft Ointment, and RINDERON-Vs Ointment) having eight thicknesses (0.0-1.5 mm) were evaluated. Dosimetry was conducted using Gafchromic EBT4 films at three anatomical locations-subclavicular, medial, and lateral aspects of the left breast.

Mean dose enhancement ratios (DERs) of 102%-116% were observed in VMAT for topical agent thicknesses of 0.1-0.5 mm, increasing to 116%-126% at 1.0 and 1.5 mm. Among the evaluated agents, StrataXRT consistently exhibited the lowest DER, with a statistically significant difference (p < 0.05).

This study demonstrated that StrataXRT exhibited the lowest DER among the evaluated topical agents in VMAT for breast cancer. Thicknesses exceeding 0.5 mm potentially exceeded the threshold dose for acute skin reactions.