The efficacy of CEA and CA15-3 tumor markers in monitoring breast cancer was evaluated in 1365 patients with either benign (n = 534) or malignant (n = 831) breast diseases. Thirty-nine breast cancer patients were monitored before and after neoadjuvant chemotherapy. Three hundred forty-nine patients were monitored during post-surgical follow-up for either a minimum of 5 years or until time of recurrence. Twenty-one patients with metastases were also monitored during chemotherapy. Elevated CA 15-3 and TPS levels were found in 28.6% and 30.0% of patients. CA 15-3 and TPS sensitivities rose to 71.9% and 66.3% in metastatic patients, respectively. The addition of TPS to CA 15-3 increased the sensitivity up to 44.4% in the overall population, and to 87.6% in patients with metastases. During post-surgical follow-up CA 15-3 was elevated in 65.7% and TPS in 61.3% of patients with recurrence. The combination of TPS and CA 15-3 increased the overall sensitivity by 12.7%. Longitudinal monitoring of metastatic patients undergoing chemotherapy demonstrated that, when positive, both CA 15-3 and TPS paralleled response to treatment. TPS monitoring may provide additional value when used in combination with CA15-3 during post-surgical follow-up of breast cancer patients.