PURPOSE/OBJECTIVE(S): To compare acute skin toxicity following post-mastectomy photon (XRT) and skin-sparing proton radiotherapy (PRT). MATERIALS/METHODS: 179 consecutive women with unilateral, non-inflammatory breast cancer were treated with conventionally fractionated post-mastectomy radiotherapy (PMRT) between 2015 and 2019. Prescription was 50 Gy (RBE) in 25 fractions to the chest wall and regional lymph nodes. PRT was administered with a median of two multi-field optimized fields (intensity modulated proton therapy). The chest wall skin was defined as the first 3 mm from the external body surface. XRT and PRT planning objectives with respect to skin were to achieve microscopic disease target coverage while limiting surface hot spots. For XRT 3-5 mm daily bolus was most commonly employed to achieve these objectives. PRT planning objectives were V90% > 90% and D1cc < 102%. Dermatitis was evaluated by physicians using CTCAE version 4.0, and patient reported outcomes (PROs) regarding skin burn severity were prospectively collected. RESULTS: Treatment was PRT in 96 and XRT in 83 (95% 3D conformal radiotherapy with a wide tangent technique, 5% intensity modulated radiotherapy). There was no significant difference between the two groups with respect to age, stage, receipt of chemotherapy, immediate breast reconstruction, diabetes mellitus, body mass index (BMI), or current or former smoking history. 65% PRT and 61% XRT pts had immediate breast reconstruction. Median follow-up was 25 months. There was no significant difference in grade ≥2 or grade 3 dermatitis between PRT and XRT at 47% vs 48%, P = 0.86 and 3% vs 7%, P = 0.22, respectively. There was a trend for higher grade ≥2 dermatitis in current or former smokers vs never smokers (60% vs 43%, P = 0.06). BMI (P = 0.11), diabetes (P = 0.41), and breast reconstruction (P = 0.63) were also not associated with grade ≥2 dermatitis. Dosimetric parameters including the skin dose to 1 cc (P < 0.0001) and 10 cc (P < 0.0001), skin V105% (P < 0.0001), and the mean skin dose (P = 0.0009) were significantly associated with grade ≥2 dermatitis. In multivariable analysis, former or current tobacco use was the only variable significantly associated grade ≥2 dermatitis (OR 2.02 [1.01-4.06], P = 0.05). Silver sulfadiazine was prescribed in 30% of PRT and 42% of XRT pts (P = 0.1). There was no difference in moderate or more severe patient-reported skin burns between PRT and XRT (40% vs 40%, P = 1.0). CONCLUSION: Post-mastectomy PRT administered with our skin-sparing technique is not associated with higher rates of acute dermatitis than XRT.
|Original language||English (US)|
|Journal||International journal of radiation oncology, biology, physics|
|State||Published - Nov 1 2021|
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging
- Cancer Research