Hormone replacement therapy, oral bisphosphonates and risk of gastrointestinal cancer


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Jane Green1,Gabriela Czanner1,Gillian Reeves1,Joanna Watson1,Lesley Wise2,Valerie Beral1
1University of Oxford, Oxford, United Kingdom,2Medicines and Healthcare products Regulatory Agency, London, United Kingdom

Background

It has been suggested that use of oral bisphosphonates may increase the risk of cancer of the oesophagus; use of hormone replacement therapy (HRT), on the other hand, has been associated with reduced risk of gastrointestinal cancers, though details remain unclear. Both groups of drugs are in common use and an appreciation of their effects on cancer risk may have implications both for understanding cancer aetiology and for public health.

Method

Case-control study nested within the UK General Practice Research Database, including 2954 men and women with oesophageal cancer, 2018 with gastric cancer and 10,641 with colorectal cancer, diagnosed between 1995 and 2005, and 5 controls per case matched for age, sex, general practice and observation time (mean 7.5 years). Conditional logistic regression was used to estimate relative risks (RRs) and 95% confidence intervals (CIs) for incident cancer in relation to prior prescribing of hormone therapy and of oral bisphosphonates, taking into account potential confounding factors such as smoking, alcohol and body mass index.

Results

Prescribing of hormone replacement therapy was associated with reduced risk of all three gastrointestinal cancers (adjusted RR for any vs no prescribing, 0.68, 95%CI 0.54-0.86, 0.83, 0.63-1.09, and 0.84, 0.76-0.92 for cancers of the oesophagus, stomach and colorectum, respectively). Cancer risks were similar for oestrogen-only and oestrogen-progestagen HRT, for current and past prescribing and by estimated duration of use.

Results in relation to bisphosphonates are currently in press (BMJ) and will be available for presentation.

Conclusion

A reduction in risk associated with prescribing of HRT was seen for cancers along the length of the gastrointestinal tract. The relative lack of variation in risk of these cancers by type or timing of HRT use contrasts with patterns of increased risk seen for cancers of the breast, ovary and endometrium.