Use of hormone replacement therapy improves the prognosis in patients with colorectal cancer: A population-based study in Sweden.

The association between hormone therapy (estrogen, with or without progesterone) and colorectal cancer (CRC) has received considerable scientific interest but previous research has generated inconsistent results. We aimed to examine whether post-diagnostic use of hormone therapy might protect against CRC mortality and all-cause mortality. Women diagnosed with CRC between January 2007 and December 2012 were identified from the Swedish Cancer Registry and linked to the Swedish Prescribed Drug Register to retrieve hormone therapy users after CRC diagnosis. A total of 1,109 patients were diagnosed with CRC and used hormone therapy post-CRC diagnosis. Time-dependent Cox regression with 1-year lag was used to calculate the hazard ratio (HR) of CRC mortality and all-cause mortality associated with post-diagnostic use of hormone therapy. Use of hormone therapy after CRC diagnosis was associated with a 26% risk reduction in CRC mortality (HR = 0.67, 95%CI 0.56-0.79) and a 30% risk reduction in all-cause mortality (HR = 0.68, 95%CI 0.59-0.77). The risk reduction was even stronger if women also used hormone therapy before the diagnosis of CRC and for women with higher cumulative doses of hormone therapy. The risk reduction was largely consistent irrespective of CRC severity. Our data suggests that use of hormone therapy after CRC diagnosis is associated with a decreased risk of cancer-related mortality and all-cause mortality.