CELL-PROLIFERATION AS A PREDICTOR OF RESPONSE TO CHEMOTHERAPY IN METASTATIC BREAST-CANCER - A PROSPECTIVE-STUDY

Many biologic prognostic markers are available for patients with breas t cancer, and considerable interest has been devoted to confirm prelim inary evidence of their role as indicators of treatment response. It r emains to be assessed whether such markers are predictors of response only to first-line or also to successive therapies. Proliferative acti vity, defined by the H-3-thymidine labeling index (TLI), was determine d on the primary lesion from 76 patients at time of first diagnosis. A t relapse, patients underwent chemotherapy as absolute (48 cases) or r elative (28 cases) first-line treatment, and their clinical response w as analyzed in relation to the TLI of the primary lesion. The objectiv e clinical response was significantly higher for rapidly (47%; CL, 33- 61%) than for slowly proliferating tumors (15%; CL, 1-29%). These find ings held true also when adjusted for metastatic site, previous treatm ent, chemotherapy regimen administered, and hormone receptor status. H owever, the direct relation between cell proliferation and benefit fro m chemotherapy held true only when such a treatment was used as an abs olute first-line approach. Cell proliferation of primary lesions repre sents a consistent indicator of response to chemotherapy over time. Pr eviously administered regimens, at least hormone therapy, could alter the proliferation-related chemosensitivity profile of individual tumor s.