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

ABSTRACT

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 accurate 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.