Abstract P1-15-18: Evaluation of separation techniques and dosimetry of the inframammary fold during whole breast radiation therapy
Authors: Guy Jones, Peter Guion, Jason Cheng, Aparna H Kesarwala
Journal: Cancer Research (2015)

Abstract Purpose/Objectives: The majority of patients receiving radiation therapy will experience some form of skin reaction, ranging from localized erythema to moist desquamation. Radiation dermatitis of the inframammary fold (IMF), the most common acute side effect of supine whole breast radiation therapy (WBRT), can be mitigated by separating the breast from the chest wall. The purpose of this analysis was an objective evaluation and comparison of practical and inexpensive separation techniques. Materials/Methods: A breast phantom was created on a human torso phantom using tissue-equivalent bolus material. Four separation techniques were evaluated: 1) taping the inferior aspect of the breast to the shoulder or placing 2) 6" x 2" rolled bubble wrap, 3) a 6" x 1" x 1" styrofoam block, or a 4) 50 mL 2" diameter plastic conical tube in the IMF. For the control setup, the breast was not taped and nothing was placed in the IMF. Written and pictorial simulation instructions recorded by one radiation therapist were independently used by additional therapists to reproduce each setup, with medial and inferior measurements taken for comparison. Dosimetry of identical tangent 100 cGy WBRT fields was evaluated with thermoluminescent dosimeters (TLDs) placed at each of four locations: the ipsilateral IMF, the ipsilateral chest wall 5 cm inferior to the IMF, and 5 cm superior to the nipple of both the ipsilateral and contralateral breasts at the 12:00 position. Measurements and TLD data are reported as mean ± standard error of the mean of 3 separate TLD readings. One-way ANOVA and posthoc analyses were used to determine significance between groups with α for significance set at p ≤0.05. Results: Compared to simulation, the average differences measured medially and inferiorly among the conical tube (10 ± 6 mm medial; 0.6 ± 0.2 mm inferior), styrofoam block (13 ± 8 mm medial; 1.2 ± 0.2 mm inferior), and bubble wrap (18 ± 4 mm medial; 0.6 ± 0.1 mm inferior) setups were not significant. The taping technique (0.2 ± 0.1 mm) was more reproducible inferiorly than the styrofoam block setup (p &amp;lt;0.01), but no different from the conical tube and bubble wrap setups. TLD readings demonstrated that the IMF received less of the prescribed dose with the taping (108 cGy ± 1.4%), styrofoam block (109 cGy ± 0.9%), or bubble wrap (110 cGy ± 0.9%) techniques compared to either the control (120 cGy ± 1.1%) or conical tube (121 cGy ± 0.4%) setups (each p &amp;lt;0.01). TLD readings from the three other locations were not significantly different between any of the setups. Conclusions: The taping, styrofoam block, and bubble wrap setups were most effective in sparing dose to the IMF. The only difference in reproducibility was between the inferior aspects of the taping and styrofoam block setups, but taping had the disadvantage of being more invasive than the other setups. While this unique analysis did not reveal a single superior solution, the taping, styrofoam block, and bubble wrap separation techniques should be considered by radiation oncologists seeking practical, inexpensive, and easily-implemented solutions to mitigate IMF dermatitis in WBRT patients. Citation Format: Guy Jones, Peter Guion, Jason Cheng, Aparna H Kesarwala. Evaluation of separation techniques and dosimetry of the inframammary fold during whole breast radiation therapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-18.