Debate over HRT link to colorectal cancer

DOUBT has been cast on whether abandoning HRT was really the reason for reduced rates of breast cancer in the wake of the Women’s Health Initiative (WHI) study.

The WHI study also found that HRT decreased colorectal cancer (CRC) risk, so rates of CRC should have gone up, researchers claim. However, that wasn’t the case, as incidence rates of colorectal cancer dropped by 5.9% even as oestrogen plus progestogen sales plummeted by 63%, contrary to the predictions of the WHI, they said in a recent paper.

However, Australian experts said their study, which involved re-analysis of WHI and comparison of colorectal cancer estimates against incidence in women older than 50 years in a US database, was methodologically flawed.

Clinical Associate Professor Karen Canfell, of Cancer Council NSW, said the analysis failed to account for effects of colorectal screening.

“Screening was increasing at exactly the same time HRT was decreasing,” she said.

Beyond that, she said, an independent review and meta-analysis by the UK’s drug regulatory authority found no statistically significant protective effect against colorectal cancer anyway.

“The best way to understand the effects is to integrate the data rather than relying on one study,” she said. 

Bond University public health expert Professor Chris Del Mar agreed the analysis omitted confounding factors including screening, and there could have been a delay in the effects of the hormones, he added.

Maturitas 2012; 71:354-59