Cancer morbidity in a cohort of 9175 Finnish women treated for infertility

BACKGROUND: Results of earlier studies on cancer risk in infertile women are inconsistent for many cancer types. Our goal was to study cancer incidence among a cohort of women treated with IVF, including ICSI and frozen embryo transfer (FET), compared with that of a control population. METHODS: A cohort of women who purchased drugs for IVF (including ICSI and FET treatments, n= 9175) in the period 1996-1998 in Finland (later called IVF women) and their age and residence-matched controls further adjusted for socio-economic position and marital status were linked to the Finnish Cancer Registry 1996-2004. RESULTS: The overall cancer incidence and combined incidence of hormonal-related breast, uterine and invasive ovarian cancers were similar among IVF women and controls. IVF women had statistically significantly less cervical cancer odds ratio (OR): 0.51, 95% confidence interval (CI): 0.30-0.85, but more skin cancers other than melanoma (OR: 3.11, 95% CI: 1.02-9.6). IVF women had three times more invasive ovarian cancers than controls, but this difference was not statistically significant, possibly due to the small number of cases. IVF women had slightly fewer breast cancers but difference was likewise not statistically significant. All cases of pulmonary cancer were diagnosed among controls (P= 0.03). CONCLUSIONS: General cancer risk or risk of hormonal-related cancers in women was not increased by IVF. The differences in certain cancers suggest a healthy patient effect or may be partly caused by residual socio-economic differences. More large studies and reanalysis of existing studies are needed to evaluate cancer risk among infertile women by subgroups regarding the cause of infertility. When evaluating risk of cancer after drug exposure, dosage and the use of different medicaments should be taken into consideration.