Interaction of tamoxifen with concurrent cytotoxic adjuvant treatment affects lymphocytes and lymphocyte subsets counts in breast cancer patients

The effects and interaction of endocrine and cytotoxic adjuvant treatment o n measures of cellular immunity were assessed in 41 stage I-II breast cance r patients from International Breast Cancer Study Group trials, Counts of l ymphocytes and lymphocyte subsets [(T, T4, T8, B, natural killer (NK) and a ctivated T (AT) cells] were assessed by flow cytometry immediately before a djuvant therapy at baseline and on day 1 of the 3rd cycle. Twenty-two patie nts received cyclophosphamide, methotrexate and 5-fluorouracil (CMF), 7 CMF and tamoxifen (TAM), and 12 TAM alone. On day 1 of the 3rd cycle the count s of total lymphocytes (P=0.003) and all lymphocyte subsets (P<0.05) except AT cells were significantly lower than baseline in the CMF treatment group . There was no significant change in the CMF+TAM or in the TAM treatment gr oup. The combination of CMF and TAM resulted in less pronounced decrease in lymphocyte and subset counts from baseline to day 1 of the 3rd cycle. It s eems possible that there is an interaction between TAM with CMF that affect s lymphocyte and lymphocyte subset counts during cytotoxic treatment.