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Published on: February 6, 2019
Comparative Analysis of Acute Skin Reactions After Postmastectomy Photon and Intensity Modulated Proton Therapy
Kimberly R Gergelis1, Arslan Afzal2, Trey C Mullikin3
1Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota; Department of Radiation Oncology, University of Rochester Medical Center, Rochester, New York.
Summary
Intensity modulated proton therapy (IMPT) and photon radiotherapy (XRT) showed comparable skin toxicity after mastectomy. XRT patients reported more skin color changes, emphasizing the need for skin dose constraints in IMPT planning.
Area of Science:
- Oncology
- Radiation Oncology
- Medical Physics
Background:
- Post-mastectomy radiotherapy is crucial for reducing local recurrence in breast cancer patients.
- Intensity modulated proton therapy (IMPT) offers potential advantages in dose distribution compared to traditional photon radiotherapy (XRT).
- Optimizing skin dose is critical to minimize treatment-related toxicity and improve patient outcomes.
Purpose of the Study:
- To compare target coverage, skin dose, physician-assessed adverse events, and patient-reported skin outcomes between IMPT and XRT in post-mastectomy breast cancer patients.
- To evaluate the dosimetric differences in skin dose distribution between IMPT and XRT.
- To assess the incidence and severity of acute dermatitis and long-term skin-related patient-reported outcomes.
Main Methods:
- A cohort of 176 women with unilateral, non-inflammatory breast cancer receiving post-mastectomy radiotherapy (50 Gy RBE) with either IMPT or XRT were analyzed.
- Skin planning objectives were established to ensure adequate coverage while minimizing dose to the skin.
- Acute dermatitis (CTCAE grade ≥2) and patient-reported outcomes (PRO-CTCAE) were compared between the two treatment modalities.
Main Results:
- Median skin doses (D0.01cc, D1cc, D10cc) were slightly higher with XRT compared to IMPT, with differences <3%.
- Acute grade ≥2 dermatitis occurred in 47% (IMPT) and 48% (XRT) (p=0.91), with grade 3 dermatitis in 3% (IMPT) and 7% (XRT) (p=0.22).
- At 12 months post-RT, XRT patients reported significantly more skin color changes (26% vs 6%, p=0.04) than IMPT patients.
Conclusions:
- Patient and provider-reported adverse skin events were mild and comparable between IMPT and XRT.
- IMPT demonstrated favorable skin dosimetry compared to XRT.
- These findings underscore the importance of implementing specific skin dose constraints during IMPT planning to optimize treatment outcomes.
