Substantial clinical and epidemiological evidence, including large meta-analyses, demonstrates that hormone replacement therapy can increase the risk of certain cancers, such as breast and ovarian cancers. At the same time, research indicates inverse or neutral associations with other specific cancer types.
The claim states that hormone replacement therapy can cause cancer. Multiple large meta-analyses (e.g., papers 1, 2, 3, 6) support this by establishing statistically significant increases in breast and ovarian cancer risk associated with hormone replacement therapy use. Although other studies find inverse associations with gastric, lung, or kidney cancers, the existence of well-documented oncogenic risks (specifically breast and ovarian cancers) fully supports the broad assertion that HRT 'can cause' cancer.