ORAL-CONTRACEPTIVES AND PROGNOSIS IN BREAST-CANCER - EFFECTS OF DURATION, LATENCY, RECENCY, AGE AT FIRST USE AND RELATION TO PARITY AND BODY-MASS INDEX IN YOUNG-WOMEN WITH BREAST-CANCER

The aim of this study was to examine associations between oral contrac eptive (OC) use, body mass index (BMI = weight/height(2)) and prognosi s in invasive breast cancer diagnosed before the age of 45. Survival a nalyses of a consecutive sample of breast cancer patients were underta ken. The cases were initially registered in a nationwide case-control study of OC use and risk of premenopausal breast cancer in Sweden and Norway. All 422 cases were under 45 years of age at diagnosis, and rec ruited from the reports to cancer registries (Sweden) or from surgical departments (Norway) during May 1984 through May 1985. Detailed infor mation about OC exposure was obtained in the initial face-to-face inte rview. With Cox's proportional hazards analyses, a significantly lower hazard rate [relative hazard (RH) = 0.54; 0.31-0.94] was seen in shor t-term users (<4 years)-but not in longterm (greater than or equal to 4 years) users-than in never-users of OC. Non-significant estimates fo r RHs lower than 1.0, i.e. better prognosis, with long recency (>5 yea rs) and latency (greater than or equal to 10 years) of OC use were not ed. Prognosis was not influenced by age at first OC use or of its timi ng in relation to the first pregnancy. A higher BMI was associated wit h a poorer prognosis, RH 5.9 (2.0-17.8) for BMI greater than or equal to 29 versus BMI < 19, but BMI was not a confounder or an effect modif ier of the association between OC use and prognosis. This study does n ot indicate that OC use prior to the diagnosis of breast cancer has an y adverse effect on the prognosis, at least not in women under 45 year s of age at diagnosis.