Background Locally advanced breast cancer (LABC) represents a heterogeneous subgroup of breast cancer with an often dismal outcome. Identifying prognostic factors has acquired great significance for the selection of optimal treatment in individual patients. Methods Between January 1993 and December 1997, 103 patients were treated in our institution with multimodality treatment consisting of neoadjuvant chemotherapy followed by surgery, adjuvant chemotherapy and radiotherapy; tamoxifen was added in hormone receptor-positive cases. In the search for prognostic factors well-established parameters (clinical, pathological and treatment-related) as well as new features with potential value (c-erbB-2, baseline serum levels of CA 15.3 and CEA) were included in the univariate and multivariate analysis. Results At a median follow-up of 92 months (range, 8-130), the estimated five-year cancer-specific overall survival (OS) and disease-free survival (DFS) were 71.34% and 57.7%, respectively. Among the 22 different variables studied, only 10 were significantly correlated with OS and DFS. In multivariate analysis five retained independent prognostic value for both OS and DFS: tumor grade, serum markers, features of inflammatory breast cancer (IBC), response to neoadjuvant chemotherapy and lymph node status. With cutoff values of 35 U/mL for CA 15.3 and 5 ng/mL for CEA, the probability of five-year OS (Cox hazard ratio 3.91, P = 0.0009) and DFS (Cox hazard ratio 2.40, P = 0.02) decreased from 78% to 52% and from 68% to 47%, respectively, when at least one of these markers was abnormal. Conclusions Baseline serum levels of CEA and CA 15.3 emerged from this study as strong independent predictors of outcome in LABC, whose value adds to other established prognostic factors such as postoperative nodal status, IBC, histological grade and response to neoadjuvant chemotherapy.