The ORs varied according to oestrogen-receptor status; the OR for a linear trend in IGF1 was significant among oestrogen-receptor positive cases (OR 1·38, 95% CI 1·14–1·68), but not for oestrogen-receptor negative tumours (OR 0·80, 0·57–1·13) and the test for heterogeneity was significant (p=0·007). The gene discussed is IGF1; the disease is neoplasm.