Radiotherapy-induced lymphocytopenia: changes in total lymphocyte count and in lymphocyte subpopulations under pelvic irradiation in gynecologic neoplasms.

Lymphocytopenia is one of the most negative biological prognostic factors in cancer patients. Lymphocytopenia may depend on tumor progression, or on various anticancer therapies. In particular, radiotherapy (RT) may induce direct lymphocyte damage. The present study was carried out to evaluate the influence of pelvic irradiation on lymphocyte number and lymphocyte subpopulations in patients with gynecologic tumors. The study included 40 patients affected by locally limited or advanced uterine tumors, who underwent pelvic irradiation for a total dose of 50.4 Gy. RT induced a significant decline in total lymphocyte number, with values lower than 500/mm3 in 29/40 (73%) patients and with a mean decrease of 71 +/- 4%. In the same way, T lymphocyte, CD4, CD8 and NK cell mean numbers significantly decreased under RT. The decline in NK and CD8 cells was limited to the first 2-3 weeks of irradiation, whereas that involving T lymphocytes and CD4 cells was progressive and persistent until the end of RT. Finally, the decline in total lymphocyte number was significantly greater in patients who had no tumor regression in response to RT. This study confirms that pelvic RT may induce severe lymphocytopenia which could negatively influence the efficacy of RT itself.