Original ResearchMenopausal hormone therapy and cancer risk: An overestimated risk?

•Menopausal hormone therapy (MHT) is the single most effective treatment for menopause-related symptoms.•Its use declined after 2002 because of a reported elevated breast cancer risk. Little is known on the overall cancer risk or other cancer types.•This contemporary MHT study showed a 9% increased cancer risk, with a decreased risk of all gastrointestinal cancer.•The cancer risk was more limited than expected, with variations for MHT types, formulations and regimens.

AimWe aimed to assess the overall cancer risk among contemporary menopausal hormone therapy (MHT) users in Sweden and the risk for different cancer types.MethodsA nationwide Swedish population-based cohort study including all 290,186 women aged ≥ 40 years having used systemic MHT during the study period (July 2005 and December 2012), compared with the Swedish female background population. MHT ever-use (all MHT, oestrogen-only MHT [E-MHT] and oestrogen plus progestin MHT [EP-MHT]) was based on the nationwide Prescribed Drug Registry. Cancer diagnoses were grouped into 16 different anatomical locations, for which standardised incidence ratios (SIRs) and 95% confidence intervals (CIs) were calculated.ResultsThe SIR of any cancer was 1.09 (95% CI: 1.07-1.11) following ever MHT, 1.04 (95% CI: 1.01-1.06) for E-MHT and 1.14 (95% CI: 1.12-1.17) for EP-MHT. The highest SIR was found for EP-MHT among users aged ≥70 years (SIR = 1.33, 95% CI: 1.26-1.40). The risk for invasive breast, endometrial or ovarian cancer combined was increased for any MHT (SIR = 1.31, 95% CI: 1.28-1.34). The risk of invasive breast cancer was increased following MHT and increased with age for EP-MHT users. The risk of gastrointestinal cancers combined was decreased (SIR = 0.90, 95% CI: 0.86-0.94), particularly the oesophagus (SIR = 0.81, 95% CI: 0.64-1.00), liver (SIR = 0.81, 95% CI: 0.65-0.99) and colon (SIR = 0.90, 95% CI: 0.84-0.95).ConclusionsMHT, notably EP-MHT, was associated with a limited increase in overall cancer risk. The increased risk of female reproductive organ cancers was almost balanced by a decreased risk of gastrointestinal cancers.