Quantification of Acute Skin Toxicities in Breast Cancer Patients Undergoing Adjuvant Proton vs. Photon Radiation Therapy: A single institutional experience
Menée auprès de 86 patientes atteintes d'un cancer du sein traité par lumpectomie ou mastectomie en combinaison avec une radiothérapie adjuvante, cette étude évalue, par rapport à une radiothérapie photonique, la toxicité aiguë cutanée d'une radiothérapie par faisceaux de protons
Background : Acute skin toxicity in the form of radiation dermatitis and/or skin hyperpigmentation is a common problem experienced by patients undergoing breast irradiation. Proton radiation has been thought to deliver higher doses to skin compared to photon radiation due to differences in the physical properties between photons and protons, however, limited literature exists directly comparing toxicity outcomes. Methods : The highest recorded grades of acute radiation dermatitis (RD) and skin hyperpigmentation (SH) were analyzed in 86 patients undergoing adjuvant radiation therapy to the breast with or without regional lymph nodes after lumpectomy (BCS) or mastectomy with either proton pencil-beam scanning (n=39) or photon (n=47) radiotherapy within a single institution to analyze differences in severity of acute skin reactions. For 34/47 photon and 33/39 proton patients, a “skin” contour was retroactively created in our treatment planning systems and multiple dosimetric parameters were calculated to quantify objective radiation doses received by skin. Results : On Chi-Square analysis, the highest reported grade of radiation dermatitis was significantly higher in women undergoing proton radiation compared to photon radiation; ≥ grade 2 RD was present in 69.2% vs 29.8% of patients receiving proton and photon therapy, respectively (p=0.002). Rates of grade 3 RD were 5.1% vs 4.3% for proton vs photon radiation, respectively (p=.848). Overall, there were no significant differences in rates of SH between modalities. There were no grade 4-5 toxicities in either cohort. Conclusions : When compared to patients receiving photon radiation, a significantly higher rate of ≥ Grade 2 RD was observed in patients undergoing proton radiation, with very low rates of grade 3 toxicity in both groups. Rates of skin hyperpigmentation did not differ significantly between modalities. Women should be counseled regarding the possibility of increased grade 2 toxicities, though this may present a dosimetric advantage for physicians when treating patients in the post-mastectomy setting, or when skin was involved on presentation.