Effects of antiestrogen and progestin on immune functions in breast cancer patients.

Several immunologic variables were evaluated in 14 patients with untreated primary breast cancer and 20 postmastectomized patients undergoing tamoxifen (TAM) or high-dose medroxyprogesterone acetate (MPA) treatment. Immunologic evaluation in the peripheral blood included lymphocyte count, definition of T-lymphocyte subsets by monoclonal antibodies (OKT3, OKT11, OKT4, and OKT8), and lymphocyte blastogenic response to phytohemagglutinin (PHA) and Concanavalin A (Con A). Moreover, the in vitro effect of TAM and MPA on the blastogenic response of peripheral lymphocytes from normal female subjects was tested. Primary breast cancer patients did not differ from controls in any of the variables tested. Similarly, the immunologic variables of the group treated with TAM were normal, with the exception of a slight reduction of the OKT4+/OKT8+ ratio. In MPA-treated patients, a reduction of the percentage of OKT4+ cells and a decrease of the OKT4+/OKT8+ ratio were observed. Moreover, response to PHA was reduced sharply. However, the addition of interleukin-2 (IL-2) to the culture medium restored PHA response. Likewise, the in vitro addition of MPA to peripheral blood lymphocytes from normal female subjects resulted in a sharp dose-dependent depression of PHA response while TAM was ineffective completely. The inhibitory effect of MPA was not evident when IL-2 was added simultaneously to the culture medium. These results show that the administration of high-dose MPA may alter immunocompetence as defined by T-lymphocyte subsets and response to mitogens. The latter effect may be related to a diminished production of IL-2. In contrast, TAM does not appear to have a significant immunodepressant action either in vitro or in vivo.