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More Evidence Links HRT to Breast Cancer

Feb 5, 2009 | Parker Waichman Alonso LLP

Studies have long been pointing to the link between Hormone Replacement Therapy (HRT) drugs like Prempro and an increase in some cancers.  Now, emerging evidence has more clearly linked the medication protocol to breast cancer, reports BBC News.

The BBC said the study found that the risk of breast cancer dropped significantly when HRT was stopped, according to New England Journal of Medicine research.  Also, an expert in the United Kingdom concluded that a 50 percent drop in HRT use likely prevented about 1,000 annual cases of breast cancer, said the BBC.

Up until now, said the BBC, findings from 2002’s broad Woman’s Health Initiative (WHI) study that said the combination of two hormones—oestrogen and progestin—were linked to an increase in breast cancer; however, experts have been unable to agree on this finding.  Frightening, because the estrogen-progestin combination is the most popularly prescribed HRT in the United Kingdom, said the BBC.  The United States stopped, for the most part, prescribing the combo HRT protocol in 2002.

The team said their research ends the questions, especially since the number of American breast cancer cases saw a steep decline following the end to combined HRT in 2002, further cementing the breast cancer-HRT link, reported the BBC.

The research followed 15,000 women who took part in the original WHI study and who ceased HRT in 2002, revealing heightened breast cancer incidences in the five years prior to 2002, but a stark drop to 28 percent in the 12 months after HRT was discontinued, said the BBC.  The team also reviewed data on women not involved in the study and who had also not been told to stop HRT and found that the 50 percent decline in those who opted to stop HRT also saw a 43 percent decline in breast cancer rates between 2002 and 2003, alone, said the BBC.  Women in this second group who continued HRT saw an increased breast cancer risk, with a doubling seen each year following the first five years. "This is very strong evidence that oestrogen plus progestin causes breast cancer.  You start women on hormones and within five years their risk of breast cancer is clearly elevated.  You stop the hormones and within one year their risk is essentially back to normal.  It's reasonably convincing cause-and-effect data, Dr. Marcia Stef
anik, from Stanford University said, quoted the BBC.

The Press Association noted that the findings present “powerful new evidence” linking breast cancer risks to post-menopausal women on long-term HRT.  The WHI trial established links between not only breast cancer and HRT, but also between HRT and blood clots and strokes, with results so convincing that the WHI was stopped three years earlier than planned, said the Press Association.  Following release of WHI trail data, HRT use declined rapidly—from 60 million to 20 million prescription from 2001 to 2005.  At the same time, breast cancer rates saw a sharp decline, which led many experts to believe there was a link between the drugs and cancer.  Some critics argued that the decline was due to an increase in mammography screenings; however, this new evidence points to an HRT link, said the Press Association.

Reuters noted that this study data presents the “strongest case yet” of the HRT and breast cancer link adding that most of the women involved in the WHI had been prescribed Wyeth’s Prempro, a combination estrogen-progesterone HRT pill.