Competing risks analyses for recurrence from primary breast cancer

The effects of prognostic factors on local, regional or distant metastasis are standardly assessed separately. Competing risks analyses may be used to assess simultaneously the effects of factors on different types of first recurrence. Data for a cohort of 678 primary invasive breast cancer patients accrued between 1971 and 1990, updated to 1995, included type of first recurrence (local, regional, distant). We investigated the effects of the traditional factors of age, tumour size, nodal status, ER, PgR, adjuvant therapy (hormones, chemotherapy, radiotherapy) on type of recurrence and time to recurrence for all patients and for those aged ≥ 65. For all ages of patients, there were five factors with significant associations with type or time to first recurrence. Adjuvant radiation was the only factor which had an effect (P ≤ 0.05) on the type of first recurrence: being associated with a reduction in local recurrence. Age, nodal status, tumour size and adjuvant chemotherapy all had significant associations across all types of first recurrence, and in particular with time to recurrence for both local and distant metastasis. This indicates a potential lack of independence in these end-points. For patients ≥ 65 years of age, there were no factors which differentially affected type of recurrence, while only nodal status and tumour size had significant associations with time to recurrence. Analyses were used to assess simultaneously the effects of traditional prognostic factors and treatment options on type of first recurrence and time to first recurrence. The extension to evaluations with newer prognostic factors would expedite the determination and mode of biologic activity for such factors.