Is age at diagnosis an independent prognostic factor for survival following breast cancer?

Background: Previous studies of patients with breast cancer have examined age at diagnosis as a prognostic factor for survival with contradictory results. The current study examines the effect of age in conjunction with pathological tumour size, lymph node status and histological grade to clarify whether age at diagnosis is an independent factor for overall survival. Methods: This is a population-based study that examines the survival of 393 women with a first diagnosis of breast cancer in 1992 in the Greater Western region of Sydney in New South Wales, Australia. Survival analysis was conducted using the Kaplan-Meier method. Relative risks associated with age at diagnosis, pathological tumour size, and number of positive lymph nodes and histological grade and adjusted for each other were computed using Cox proportional hazard regression. Patients' ages were categorized as 'younger' (< 40 years of age at diagnosis), 'middle-aged' (40-69 years) or 'older age' (> 69 years). Results: The 10-year survival of women < 40 years was 49%, which was significantly lower than 'middle-aged' women (73%). For women with node-negative breast cancer, younger women had a significantly (P = 0.011) poorer survival rate (68%) than middle-aged (90%) or older women (80%). After adjusting for the effects of the pathological tumour size, the lymph node status and histological grade, women < 40 years showed a higher risk of dying than older women. However, young women detected with a small (< 20 mm) node-negative tumour have a good prognosis. Conclusions: Age at diagnosis, tumour size and lymph node status were independent prognostic indicators for survival. Age at diagnosis should be considered as an important factor in making decisions about adjuvant therapy, irrespective of nodal status.