No association found between fertility treatment, some types of cancer
Over 8.8 years of follow-up, researchers in Great Britain found no significant increase in risk for uterine cancer, breast cancer overall, or invasive breast cancer in women who had undergone hormone-based assisted reproduction.
Hormone-based assisted reproduction does not appear to be associated with uterine or invasive breast cancer, a new study found.
Researchers performed a population-based study using a national database of all women who had undergone assisted reproduction in Great Britain from 1991 to 2010. Fertility records were linked to records in national cancer registries, and observed first diagnoses of ovarian, breast, and uterine cancer were compared. Standardized incidence ratios (SIRs) were calculated according to age, sex, and period-specific incidence rates nationally. The study results were published July 11 by the BMJ.
Overall, 255,786 women with 2,257,789 person-years of follow-up were included in the study. Average follow-up was 8.8 years, and 41% of women were followed for at least 10 years. Patients' average age at first treatment was 34.5 years. Over 8.8 years of follow-up, the researchers found no significant increase in risk for uterine cancer (SIR, 1.12; 95% CI, 0.95 to 1.30), breast cancer overall (SIR, 0.98; 95% CI, 0.94 to 1.01), or invasive breast cancer (SIR, 0.96, 95% CI, 0.92 to 1.00). An increasing number of fertility treatment cycles was associated with increased risk of in situ breast cancer (SIR, 1.15; 95% CI, 1.02 to 1.29), as well as with an increased risk of invasive and borderline ovarian cancer (SIR, 1.40 [95% CI, 1.24 to 1.58] and 1.36 [95% CI, 1.15 to 1.60], respectively). However, higher risk for ovarian tumors was seen only in women with endometriosis, low parity, or both.
The researchers noted that their results might have differed if follow-up had been longer and that more demographic information on the study participants would have been useful, among other limitations. They concluded that their study found no increased risk of uterine or invasive breast cancer in women who had undergone assisted reproduction but did find an association between risk of in situ breast cancer associated with number of treatment cycles, as well as an association between assisted reproduction and all types of ovarian cancer. For ovarian cancer, however, they noted that the finding was probably due to patient characteristics rather than to the treatment itself and that they “were not able to distinguish between a genuine risk of borderline ovarian tumours and other explanations including surveillance bias.” They called for further studies with longer follow-up in this population.