Purpose: Radiotherapy is essential for the treatment of breast cancer (BC). However, adverse effects may occur in healthy tissue, during treatment and even after several months. Although it is known that this clinical radiosensitivity is multifactorial, the factors involved are unknown yet. In this study, we evaluated the effect of these factors on the development of radiodermatitis in patients undergoing radiotherapy. Materials and Methods: Demographic and lifestyle data collected during face-to-face interviews of 122 BC patients and data from clinical records were investigated. Most patients underwent conventional three-dimensional radiotherapy treatment. A total dose of 50 Gy was administered (2 Gy/day), followed by a boost in a tumor bed with a total dose of 18 Gy (2 Gy/day). Radiotoxicity was evaluated weekly using the Radiation Therapy Oncology Group classification system (range, 0 to 4, according to the severity). Results: In the present study, 75.4% of patients presented acute skin toxic effects with different degrees of severity. In 25% of cases, these effects manifested at the end of the fourth week at a cumulative dose of 40 Gy. The association of grade ≥2 acute skin reactions with body mass index (BMI) and breast size and between grade 3–4 and age was positive compared with controls. However, the role of the other factors could not be confirmed. Conclusion Analysis of the factors related to individual radiosensitivity suggests that age, BMI and breast size play an important role in the development of acute skin toxicity during treatment. Particular attention to patients who present these characteristics would help to control treatment effectiveness and therefore optimize their quality of life.

PURPOSE: Reactive oxygen species (ROS) are generated as an indirect product of radiation therapy (RT). Genetic variation in genes related to ROS metabolism may influence the level of RT-induced adverse effects. We evaluated the potential association of single nucleotide polymorphism (SNP)-related response to radiotherapy injury in breast cancer patients undergoing RT. MATERIALS AND METHODS: Eighty patients receiving conventional RT were included. Acute effects were evaluated according to the Radiation Therapy Oncology Group (RTOG) scores. DNA was extracted from blood and buccal swab samples. SNPs were genotyped for GSTP1, GSTA1, SOD2, and NOS3 genes by polymerase chain reaction-based restriction fragment length polymorphism. Univariate analysis (odds ratios [ORs] and 95% confidence interval [CI]) and principal component analysis were used for correlation of SNPs and factors related to risk of developing ≥ grade 2 acute effects. RESULTS: Sixty-five patients (81.2%) showed side effects, 32 (40%) presented moderate to severe acute skin toxicity, and 33 (41.2%) manifested minimal acute skin reactions by the end of treatment. In both univariate and multivariate analyses, nominally significant associations were found among body mass index (OR, 3.14; 95% CI, 8.5338 to 1.1274; p=0.022), breast size (OR, 5.11; 95% CI, 17.04 to 1.54; p=0.004), and grade ≥ 2 acute radiation skin toxicity. A significant association was also observed between NOS3 G894T polymorphism (OR, 9.8; 95% CI, 211.6 to 0.45; p=0.041) and grade ≥ 2 acute radiation skin toxicity in patients with neo-adjuvant chemotherapy treatment. CONCLUSION: The analysis of the factors involved in individual radiosensitivity contributed to the understanding of the mechanisms underlying this trait.
Body Mass Index ; Breast Neoplasms* ; Breast* ; DNA ; Drug Therapy ; Genetic Variation ; Humans ; Metabolism ; Multivariate Analysis ; Oxidative Stress* ; Polymorphism, Restriction Fragment Length ; Polymorphism, Single Nucleotide ; Principal Component Analysis ; Radiation Tolerance ; Radiotherapy* ; Reactive Oxygen Species ; Skin