Marco Tampellini, Alfredo Berruti, Raffaella Bitossi, Gabriella Gorzegno, Irene Alabiso, Alberto Bottini, Antonio Farris, Michela Donadio, Maria Sarobba, Enrica Manzin, Antonio Durando, Enza Defabiani, Andrea De Matteis, Mara Ardine, Federico Castiglione, Saverio Danese, Elena Bertone, Oscar Alabiso, Marco Massobrio, and Luigi Dogliotti
Summary Tumor response to first-line chemotherapy in advanced breast cancer offers prognostic information and may be used as a surrogate marker for evaluating treatment efficacy. With this study we wanted to determine whether changes in circulating serum CA 15-3 levels during chemotherapy provided additional information for prognostic prediction. Serum CA 15-3 was measured at baseline and after 3 and 6 months during anthracycline-based first-line chemotherapy in 526 patients with advanced breast cancer prospectively enrolled in five phase II-III trials. Changes in marker levels were correlated with disease response, time to progression and overall survival. In all, 336 patients attained a disease response. A significant relationship was found between disease response and CA 15-3 variations, although many individual discrepancies were also observed. At the 6-month time point, the median time to progression was 15.3 months in patients with normal marker levels throughout the study, 11.7 months in those with a CA15-3 reduction >25%, 9.6 months in those with elevated baseline CA 15-3 levels which did not change during therapy and 8.6 months in those with increased marker levels (p < 0.001). The median survival was 42.3, 29.7, 28.5, and 24.8 months, respectively (p < 0.002). The prognostic role of changes in CA 15-3 levels was maintained in the patient subset attaining disease response or stabilization to treatment (p < 0.001) and after adjusting for clinical response and major prognostic parameters in the multivariate analysis (p < 0.001). In conclusion, monitoring serum CA 15-3 levels during first-line chemotherapy in advanced breast cancer patients provides prognostic information independently from tumor response. [ABSTRACT FROM AUTHOR]