PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s):Proton therapy has been shown to have higher skin dose compared to photon therapy due to physical property differences between photon and proton energy deposition. We sought to analyze rates of acute radiation dermatitis (RD) and skin hyperpigmentation (SH) in patients undergoing adjuvant radiation therapy (RT) to the breast after lumpectomy (BCS) or mastectomy in locally advanced breast cancer (LABC).
Materials/Methods:A retrospective database was constructed of consecutive patients diagnosed with LABC treated with either proton or photon radiation between September 2015 and December 2017. Patients were excluded based on receipt of hypofractionation, re-RT, or lack of recorded acute toxicity data. Skin toxicity was scored using CTCAE v 4.0 criteria on a weekly basis during on-treatment visits. This highest recorded RD and HP toxicity was analyzed for each patient, and chi-square analysis and logistic regression were performed. Results: Eighty-six patients (39 proton, 47 photon) met inclusion criteria and were available for analysis. Median age was 53 y (range, 24-78y), median RT dose was 60 Gy (range, 45-80 Gy), RT fraction size ranged 1.8-2.0 Gy per fraction. An imbalance between race existed on chi-square, with more black patients receiving photon radiation. Body mass index, smoking status, ECOG PS, diabetes mellitus, stage, radiation dose, use of concurrent or neoadjuvant chemotherapy and boost radiation were equivalent between groups. On chi-square analysis, ≥ grade 2 RD was present in 69.2% vs 29.8% of patients receiving proton and photon therapy, respectively (p=0.002, Table 1). Rates of grade 3 RD were 5.1% vs 4.3% for proton vs photon radiation, respectively. In white patients where erythema is more prominent, the rate of ≥ grade 2 RD was 55% vs 34% in black patients where hyperpigmentation is more prominent (p=0.056). There were no significant differences in rates of SH between modalities. There were no grade 4-5 toxicities. Conclusion: When compared with patients receiving photon therapy, a higher rate ≥ grade 2 dermatitis was seen in patients undergoing proton therapy. Rates of grade 3 toxicity were very low in both groups. This transient increased acute toxicity is managed conservatively and did not result in treatment breaks or increased healthcare expenditures. Women should be counseled regarding the possibility of increased grade 2 toxicities; however this does not outweigh the dosimetric heart and lung benefits seen in proton therapy. Table 1: Highest recorded acute skin toxicities by modality
|Photon (n=47)||Proton (n=39)|
|Highest CTCAE Grade||0-1||≥2||0-1||≥2||p-value|
|Radiation Dermatitis||33 (70.2%)||14 (29.8%)||12 (30.8%)||27 (69.2%)||p=0.002|
|Skin Hyperpigmentation||41 (87.2%)||6 (12.8%)||36 (92.3%)||3 (7.7%)||p=0.41|
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