Influence of tumor location on breast cancer prognosis

A clinical series from the Milan National Cancer Institute,1 as well as the large database of the Danish Breast Cancer Cooperation Group (DBCG)2 indicated that breast cancer localized in the upper lateral quadrant had better prognosis than those located elsewhere in the breast. Nodular status, tumor size, histological grading and patients' age were unable to explain the difference in survival. Because the differences were relatively limited (of the order of 20%), although of potential clinical relevance, independent confirmation from other population-based series would be of importance. We have therefore considered the influence of tumor location on breast cancer survival using data from the Swiss Cancer Registry of Vaud. The catchment population of the Vaud Cancer Registry numbered 602,000 in 1990. Population-based incidence data have been available since 1974. The registry is tumor-based and multiple primary malignancies found in the same person are entered separately. The basic information available for each comprises socio-demographic characteristics of the patient (age, gender), the primary site and histological type of the tumor according to the standard International Classification of Diseases for Oncology, Ninth Revision, (ICD-O. 9)3 and the date of the diagnosis.4 The present series includes 4,562 patients with breast cancer diagnosed between 1989 and 1999. These women's records were actively followed-up through to the end of 1999 to check for emigration or death.5 The product limit (maximum likelihood) method was used to obtain survival rates. Moreover, multivariate hazard ratios, as estimators of relative risk (RR), (and corresponding 95% confidence intervals [CI]) of death are given. Included in the proportional hazard models were terms for nodal status, tumor size (<2, 2 to ≤5, >5 cm), histological grading (I, II + III, other or unknown), age at diagnosis (in years) and year of diagnosis. Table I gives the distribution of 4,562 incident breast cancer cases according to location and selected tumors' characteristics. Tumors located in the lateral quadrant were more frequently nodal positive than medial ones, whereas no difference was observed with reference to tumours' size and histological grading. Five-year crude survival was 78% for neoplasms in the upper lateral quadrant, 79% for those in the lower lateral, 77% in the upper medial and 70% in the lower medial. The difference was statistically significant (p = 0.018). Table II gives the fully adjusted relative risk of dying of breast cancer according to tumor quadrant location. As compared to tumors located in the upper lateral quadrant, the RR was 1.23 (95% CI = 1.07–1.43) for other locations. The RR was 1.20 for lower lateral, 1.02 for upper medial and 1.55 for lower medial. A tendency for lower survival in lower and medial quadrants was also observed across strata of nodular status, although the random variation was greater due to small absolute numbers, The present, population-based dataset therefore confirms that, although crude survival is not consistently related to quadrant location, breast cancer prognosis is more favorable for neoplasms in the upper lateral quadrant than for other locations, when allowance is made for nodal status and other tumor characteristics. This may be related to differences in lymphatic drainage, incomplete removal of tumor tissue in women with tumors distant from the axilla, or to other factors of prognostic importance.2 The confirmed observation of these prognostic differences indicates that tumor location should be included in any multivariate model as an additional factor in breast cancer management and treatment. Yours sincerely, The contribution of the Vaud Cancer Registry's staff is gratefully acknowledged. Fabio Levi, Lalao Randimbison, Van-Cong Te, Carlo La Vecchia