IMPACT OF CHRONOMODULATED RADIOTHERAPY ON ACUTE SKIN TOXICITY IN CHEST WALL IRRADIATED BREAST CANCER PATIENTS – A SINGLE INSTITUTION ANALYSIS.

Abstract: We explored the possible association between the timing of delivery of radiation and the grade of skin reaction that develops in breast cancer patients receiving chest wall irradiation as adjuvant treatment after modified radical mastectomy. Invasive breast cancer patients, registered during the period of January 2013 – December 2014, who had undergone modified radical mastectomy followed by chest wall irradiation, were eligible for inclusion to the study. All the patients received chest wall external beam radiotherapy (EBRT) to a dose of 50 Gy in 25 fractions, one fraction a day, five days a week, delivered as tangential opposed pair, from a Cobalt 60 teletherapy source. Patients were stratified based on whether they received EBRT in the morning (between 8 am – 11 am) or in the evening between (5 pm – 8 pm). The clinicopathological characteristics of patients in both the arms were relatively well balanced.

The incidence of higher grade of skin reaction (grade 3 or 4) was 22.5 % compared to 35.7 % in the morning and evening arms respectively, which was statistically significant (p = 0.039). The time to development of Grade 3 or 4 toxicity was 4.44 weeks compared to 4.11 weeks in the morning and evening arms respectively, suggesting that higher toxicity developed earlier in the patients receiving EBRT in the evening, though not statistically significant (p = 0.29).