Dose-volume predictors of radiation dermatitis in patients undergoing radiotherapy after radical mastectomy for breast cancer

Abstract

Abstract Purpose To analyze incidence and dose-volume predictors of acute radiation dermatitis (ARD) in patients with breast cancer who undergo regional nodal irradiation. Methods and materials: Patients treated with Intensity-modulated radiation therapy (IMRT) in the chest wall, supraclavicular/subclavicular fossa, secondary axilla, and/or intramammary link after mastectomy were included. The prescribed dose was 50 Gy in 25 fractions. ARD was evaluated and graded once during radiotherapy(RT), 1 week after RT, and at the 1 month follow-up. Grading was performed according to the National Cancer Institute Common Toxicity Criteria for Adverse Events version 3.0. Total skin volume, mean dose, maximum dose, relative volume (RV5-RV45) and absolute volume (AV5-AV45) in patients receiving at least 5 to 45 Gy in 5 Gy increments were assessed. Univariate and multivariate logistic regression analyses were performed to identify risk factors for ARD and to obtain ROC curves. Thresholds for skin dosimetry parameters were determined. Results A total of 134 patients with breast cancer who received recruited RT were included in this analysis. Among all patients the incidence of ≥ 2 ARD was 33.58% (45/134), of which the incidence of grade 2 ARD was 32.09% (43/134), and the incidence of grade 3 RD was 1.49% (2/134). No grade 4 or 5 ARD was observed. After univariate and multivariate analyses, age, BMI, BSA, sex, tumor laterality, vascular cancer embolus, nerve invasion, adjuvant chemotherapy were not significantly associated with the risk of grade ≥ 2 ARD. Internal mammary nodal irradiation (IMNI) (P = 0.049) and targeted therapy (P = 0.005) were independent risk factors for ARD. AV35 (P = 0.030) and AV40 (P = 0.025)of the skin were significantly associated with the risk of grade ≥ 2 RD. According to the ROC curves, the optimum thresholds were 199 mL for AV35 and 181.8 mL for AV40, respectively. Conclusion The receipt of targeted therapy during radiation therapy and IMNI are risk factors for the development of grade 2 ARD. Maintaining AV35 on the upper skin at < 199 mL and AV40 at < 181.8 mL may decrease the risk of ARD.