Lymphocyte depletion during treatment with intensive chemotherapy for cancer

Recently we have observed an increased incidence of opportunistic infections in patients treated with intensive chemotherapy for cancer. Because T-cell depletion is associated with similar clinical events in human immunodeficiency virus infection and after bone marrow transplantation, we have analyzed peripheral blood lymphocyte populations in a series of patients during treatment with intensive chemotherapy for cancer. Although neutrophil, monocyte, and platelet numbers consistently recovered to greater than 50% of pretreatment values after each sequential cycle of therapy, lymphocyte numbers did not recover within the same time period. B cells decreased rapidly from a mean value of 149 ± 46/mm³ before chemotherapy to 4 ± 1/mm³ during chemotherapy (P = .01). CD4⁺ T cells decreased from a mean of 588 ± 76/mm³ before chemotherapy to 105 ± 28/mm³ during chemotherapy (P = .0002) and CD8⁺ T cells decreased from a mean of 382 ± 41/mm³ before chemotherapy to 150 ± 46/mm³ during chemotherapy (P = .0009). Natural killer cell numbers did not show significant declines (171 ± 30/mm³ before, 114 ± 24/mm³ during, P = .19). Based on the history of opportunistic complications in patients with other disorders who display similar degrees of CD4⁺ T-cell lymphopenia and preliminary observations in this population, immune incompetence could surface as a dose-limiting toxicity for highly dose-intensive chemotherapy regimens.