CANTO skin: Evaluation of skin toxicity risk factors in patients treated for breast cancer.

Skin reaction is a common toxicity during oncology management, especially followed during the radiotherapy. Its assessment and understanding of the factors influencing its occurrence, is a major issue in the management of patients treated for an early breast cancer (BC). We evaluated 8561 patients during their overall management for a BC. We focus on specific skin toxicities: erythema, fibrosis, telangiectasia and changes of skin colour. These toxicities were assessed at the baseline defined as 0-3-6 (M0), 12 (M12), 36 (M36) and 60 (M60) months. The prevalence of toxicities of interest varied over time, so at M0, 30.4% of patients had erythema while 17.7% of patients had fibrosis. At M60, the prevalence of erythema was 2%, while fibrosis remained stable at about 19%. After adjustments, at M0, there was a significant association between the onset of cutaneous erythema and obesity, the presence of axillary dissection, the type of surgery and the tumour phenotype RH+/HER2+. Concerning fibrosis, a significant association was found, at M12, with the age of the patient, obesity, Charlson score and type of surgery. Concerning the modification of skin colour at M12, we find a link between the age of the patient, obesity, tobacco consumption and alcohol consumption. The prevention of this toxicity is a major issue for the quality of life. Our results allow us to understand the risk of developing skin toxicity in a patient, depending on her intrinsic, tumour or therapeutic characteristics and to implement adapted means of prevention and monitoring.

CANTO-RT: Skin toxicities evaluation of a multicentre large prospective cohort of irradiated patients for early-stage breast cancer.

Skin damage is the most common and most important toxicity during and after radiation therapy (RT). Its assessment and understanding of the factors influencing its occurrence, is a major issue in the management of patients irradiated for an early breast cancer. CANTO is a prospective clinical cohort study of 10 150 patients with stage I-III BC treated from 2012 to 2017 in 26 cancer centres. In our study, we used CANTO-RT, a subcohort of CANTO, including 3480 patients who received RT. We are focus on specific skin toxicities: erythema, fibrosis, telangiectasia and cutaneous pigmentation. The prevalence of toxicities of interest varied over time, so at baseline for early toxicity Month (M) 0-3-6, 41.1% of patients had erythema while 24.8% of patients had fibrosis. At M12 and M36, the prevalence of erythema decreased, respectively, while fibrosis remains stable. The prevalence of telangiectasia increases from 1% to 7.1% from M0-3-6 to M36. After adjustments, we showed an association between the occurrence of skin erythema and obesity; the type of surgery; the presence of axillary dissection; the use of taxane-based CT and the 3D vs IMRT irradiation technique. Regarding fibrosis, an association is found, at M0-3-6, with age at diagnosis, obesity, tobacco and the use of boost. Only obesity and the type of surgery received by the patient remained statistically significant at M12 and M36. In our study we identified several risk factors for acute and late skin reactions. The use of a boost was mainly related to the occurrence of fibrosis while the use of IMRT-type technique decreased the occurrence of skin erythema.