Dosimetric and On-treatment Clinical Results of a Volumetric-based Skin-sparing Planning Technique for Patients Treated to the Breast and Chest Wall With Pencil-Beam Scanning Proton Therapy

Overview

Journal Adv Radiat Oncol

Date 2025 Jan 13

PMID 39802863

Authors

Avani D Rao

Alexander Goughenour

Betelehem Kebede

Caroline Bamberger

Grayden MacLennan

Jackeline Castro

Lisa Stephenson

Amanuel Negussie

Sydney Seracino

Hongkun Wang

Stella Hetelekidis

Sarah J Gao

Lonika Majithia

Ashish Chawla

Ashkan Parniani

Peng Wang

Jiajin Fan

Affiliations

Soon will be listed here.

Abstract

Purpose: This study evaluates the hypothesis that a volumetric skin-sparing planning technique (SSPT) will reduce acute dermatitis in patients treated to the breast or chest wall (CW) with proton pencil-beam scanning (PBS).

Methods And Materials: In January 2022, our center incorporated volumetric-based skin-sparing objectives in addition to skin hot spot evaluation as an SSPT. The SSPT incorporated an objective to limit the volume of a skin evaluation structure (skin-eval) receiving 95% of the prescription dose or more (V95%Rx) to ideally < 50%. We compared target coverage, robustness, skin-eval dosimetry, and acute on-treatment skin toxicity in patients treated with and without incorporation of this SSPT. Patients with skin/dermal lymphatic invasion or inflammatory breast cancer were excluded.

Results: A total of 84 patients who received breast/CW PBS were included (43 planned without and 41 with the SSPT). There was no difference in percentages of patients treated with intact breast/CW/immediate CW reconstruction between groups. Mean skin-evalV95%Rx was 72% vs 30%, < .0001, for those treated without versus with an SSPT. Maximum %Rx to the skin-eval volume of 0.03, 0.3, and 1 cc was higher in patients treated without versus with an SSPT (103.1% vs 101.5%; 101.3% vs 100.4%; and 101.8% vs 99.7% [all ≤ .0001]), respectively. There was a small difference in the mean clinical target volume V97.5%Rx in patients treated without versus with the SSPT (97.8% vs 96.5%, = .0003). Patients planned using the SSPT demonstrated reduced rates of grade 1 breast pain at week 2 (12% vs 33%, = .0424) and grades 2 and 3 dermatitis at weeks 4 and 5 (week 4 dermatitis ≥ grade 2, 18% vs 43%, = .0224; week 5 dermatitis ≥ grade 2, 45% vs 69%, = .0006). There were numerically more patients requiring a treatment break or not completing the full intended prescription (4 vs 1) in the pre-SSPT cohort.

Conclusions: The use of an SSPT may reduce acute skin toxicity in patients with breast cancer treated with PBS.

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