Early Toxicity in Patients Treated With Postoperative Proton Therapy for Locally Advanced Breast Cancer

Abstract

Purpose To report dosimetry and early toxicity data in breast cancer patients treated with postoperative proton radiation therapy. Methods and Materials From March 2013 to April 2014, 30 patients with nonmetastatic breast cancer and no history of prior radiation were treated with proton therapy at a single proton center. Patient characteristics and dosimetry were obtained through chart review. Patients were seen weekly while on treatment, at 1 month after radiation therapy completion, and at 3- to 6-month intervals thereafter. Toxicity was scored using Common Terminology Criteria for Adverse Events version 4.0. Frequencies of toxicities were tabulated. Results Median dose delivered was 50.4 Gy (relative biological equivalent [RBE]) in 5 weeks. Target volumes included the breast/chest wall and regional lymph nodes including the internal mammary lymph nodes (in 93%). No patients required a treatment break. Among patients with >3 months of follow-up (n = 28), grade 2 dermatitis occurred in 20 patients (71.4%), with 8 (28.6%) experiencing moist desquamation. Grade 2 esophagitis occurred in 8 patients (28.6%). Grade 3 reconstructive complications occurred in 1 patient. The median planning target volume V95 was 96.43% (range, 79.39%-99.60%). The median mean heart dose was 0.88 Gy (RBE) [range, 0.01–3.20 Gy (RBE)] for all patients, and 1.00 Gy (RBE) among patients with left-sided tumors. The median V20 of the ipsilateral lung was 16.50% (range, 6.1%–30.3%). The median contralateral lung V5 was 0.34% (range, 0%–5.30%). The median maximal point dose to the esophagus was 45.65 Gy (RBE) [range, 0–65.4 Gy (RBE)]. The median contralateral breast mean dose was 0.29 Gy (RBE) [range, 0.03–3.50 Gy (RBE)]. Conclusions Postoperative proton therapy is well tolerated, with acceptable rates of skin toxicity. Proton therapy favorably spares normal tissue without compromising target coverage. Further follow-up is necessary to assess for clinical outcomes and cardiopulmonary toxicities.

Radiotherapy induced dermatitis is a strong predictor for late fibrosis in head and neck cancer. The development of a predictive model for late fibrosis

“…There is some evidence that silver sulfadiazine cream can reduce dermatitis score [14]. Another possibility to limit the incidence of early radiodermatitis besides topical products is the use of new RT techniques such as proton RT [15] or adaptation of the treatment, in order to limit the dose to the neck as much as possible, when patients experience more than average early symptoms [11]. This can be done by using adaptive replanning or by changing to other treatment modalities such as proton planning where available in case of more than average early toxicity [11].…”

Proton Therapy for Breast Cancer: Progress & Pitfalls

“…The rates of acute grade 1, 2 and 3 esophagitis were 31, 33 and 0%, respectively. Like others the authors noted that their PBT delivery techniques were optimized over the course of the study period, suggesting that outcomes will only continue to improve as the field gains experience with PBT [65,68]. In summary, these promising reports suggest that the acute toxicity profile of PBT compares favorably compares with photons.…”

“…Of note, the authors modified their target volumes around the esophagus after the first five patients to minimize overlap, and this appeared to reduce the esophagitis risk. With 9 months of follow-up, there were no rib fractures or reported chest wall toxicity [65].…”

“…Whole breast/chest wall & RNI A small number of patients treated with whole breast plus RNI have been reported in the literature [65]. However, due to the small numbers and short follow-up, no clear conclusions can be made regarding toxicity, long-term cosmesis or optimal techniques for delivery.…”

Proton radiotherapy for treating the most common carcinomas

“…Proton radiotherapy, as compared with the photon counterpart, allows a more homogeneous irradiation with a high dose target volume with limited doses delivered to the heart, lung and the opposite breast which is a particular advantage of IMPT [70][71][72][73]. This is particularly relevant for clinical situations where irradiation of regional lymph nodes is required.…”