Lymph nodes in the irradiated field influence the yield of radiation-induced chromosomal aberrations in lymphocytes from breast cancer patients

Purpose: To measure chromosomal aberrations in blood lymphocytes from breast cancer patients treated with radiotherapy after quadrantectomy or tumorectomy. Methods and Materials: Twenty-two breast cancer patients treated with breast-conserving surgery and radiation were evaluated. Adjuvant chemotherapy was also given to 9 patients. Blood samples were obtained before radiotherapy, after about one-half of the fractions, and at the end of the treatment of the whole breast (50 Gy). Chromosome aberrations in peripheral blood lymphocytes were measured using chemical-induced premature chromosome condensation combined with fluorescence in situ hybridization. Results: Radiation treatment produced a significant increase in the yield of chromosomal aberrations. A large interindividual variability was observed. The variability was not related to field size, previous chemotherapy, or treatment morbidity. Chromosome aberrations in lymphocytes at the end of the treatment were significantly higher in the group of patients with no lymph nodes surgically removed before the treatment than in the group of patients with more than 10 lymph nodes removed. Conclusions: The number of lymph nodes within the radiation field is an important factor affecting the yield of radiation-induced chromosomal aberrations in breast cancer patients.