The clinical relevance of static disease (no change) category for 6 months on endocrine therapy in patients with breast cancer

This study reports on the clinical relevance of the static disease (SD) category in 255 breast cancer patients on endocrine therapy. All patients had received first- and second-line endocrine therapy and were assessed for response by the International Union Against Cancer (UICC) criteria. We did not include patients who received first-line endocrine therapy but did not or have not yet proceeded to second-line hormone therapy, e.g. died from rapidly progressive disease, started chemotherapy for rapidly progressive disease, remained in long-term remission on first-line endocrine therapy. We analysed survival from initiation of first-line endocrine therapy by the remission criteria, i.e. complete response (CR), partial response (PR), static disease (SD) or progressive disease (PD), achieved on that therapy. Patients were divided into those with metastatic breast cancer (MBC) and non-metastatic disease. There was no significant difference in survival from starting first-line endocrine therapy between patients who obtained CR, PR or SD: all three groups of patients survived significantly longer than patients who showed PD within 6 months (all P < 0.0001 except CR versus PD [MBC] which was P < 0.002). Equally, for second-line endocrine therapy there was no difference in survival between patients who obtained CR, PR or SD: all three groups (CR, PR and SD) survived significantly longer than PD (all P < 0.0003 except for CR versus PD which was P < 0.003 for non-metastatic and P < 0.059 for MBC). Durable SD appears to be a clinically useful criteria of therapeutic remission.