A systemic effect of localized postmastectomy radiation upon the lymphocyte is described. Total lymphocytes were determined in 103 women preoperatively and two or more years after mastectomy. The total lymphocyte count of those not radiated was unchanged, but in the radiated patients it decreased. At time of recurrence, the count of those not radiated was unchanged and of those radiated showed a decrease. Low counts may persist for more than ten years after radiation. The failure of radiation to improve survival after mastectomy may be a consequence of an induced defect in cellular immunity, as reflected in the decrease of lymphocytes, that negates the tumor destructive effect of radiation. The reported reduction in responsiveness of breast cancer metastases to hormone therapy may be a consequence of the widespread use of postmastectomy radiation.
Meyer KK. Radiation-Induced Lymphocyte-Immune DeficiencyA Factor in the Increased Visceral Metastases and Decreased Hormonal Responsiveness of Breast Cancer. Arch Surg. 1970;101(2):114-121. doi:10.1001/archsurg.1970.01340260018003