The importance of surgery and accurate axillary staging for survival in breast cancer.

Aims. The purpose of this study was to investigate, within the context of the Danish Breast Cancer Cooperative Group (DBCG) programmes, whether a dedicated surgical approach had a significant bearing on the outcome of breast cancer treatment. Methods. From 1 January 1980 to 31 December 1990, patients below 70 years of age with operable breast cancer from, Odense University Hospital ( n = 743) were compared with those from the rest of Denmark (denoted rest-DK) ( n = 15,419). All patients were treated according to nationwide DBCG guidelines and reported to the DBCG Data Centre. The potential median observation time was 11.2 years (range 6.0–16.9). Patients underwent mastectomy or breast conserving therapy, and high risk lymph-node positive patients had adjuvant systemic therapy with or without radiotherapy. Results. Comparing total patients series, overall survival (OS) was significantly superior in patients from Odense compared with rest-DK ( P = 0.02), with 10-year OSs of 62% (95% CI: 58–65%) and 56% (55–57%), respectively. In subgroups, the OS of low-risk node negative patients (protocol A) in Odense compared with rest-DK was significantly better ( P = 0.02); 10-year OS was 78% (73–84%) versus 72% (70–73%). Among the high-risk pre-menopausal patients (protocol B), the OS was significantly better in Odense ( P = 0.009); 10-year OS was 67% (60–75%) versus 53% (51–55%) in rest-DK. Post-menopausal high-risk patients (protocol C) did not differ significantly in OS between Odense and rest-DK ( P = 0.61). Locoregional control in the Odense series was superior compared with rest-DK. More lymph nodes were recovered and examined from the axilla in the Odense series than in rest-DK, a median of 10 vs. 6 nodes. In the Odense series, a significantly higher proportion of pre-menopausal patients had positive lymph nodes, predominantly one to three positive nodes, and subsequently a lower proportion of pre-menopausal patients had negative lymph nodes compared with rest-DK ( P = 0.02), indicating a more accurate staging in Odense vs. rest-DK. The survival benefit among the patients from Odense cannot be explained by stage migration alone, but seems to represent a true survival advantage. Overall mortality was significantly lower in the Odense series compared with rest-DK. Whether or not this difference could be explained by lower background mortality in the Odense series or was caused by superior treatment is discussed. Conclusions. The extent of surgery seems important for locoregional tumour control and acurate axillary lymph-node staging. In combination, these might lead to superior recurrence-free and overall survival, although differences in background mortality cannot be ignored. Surgery, therefore, might represent a risk factor by itself.