SAN ANTONIO — Breast cancer patients who used menopausal hormone therapy before their diagnosis had a reduced breast cancer mortality, compared with never-users of hormone therapy, in the large epidemiologic California Teachers Study.
Users of estrogen plus progestin hormone therapy who developed breast cancer had an unadjusted 63% relative risk reduction in breast cancer-specific mortality, compared with HT never-users with the malignancy. The fully adjusted reduction in the risk of breast cancer mortality in patients with a history of estrogen-progestin HT was 47%, compared with HT never-users, Sarah F. Marshall reported at the San Antonio Breast Cancer Symposium.
In breast cancer patients with a history of estrogen-only HT use, the unadjusted relative risk reduction in mortality due to breast cancer was 36%, compared with HT never-users. However, upon fully adjusting for race, lymph node status, comorbidities, type of treatment, smoking, body mass index, and physical activity, as well as tumor stage, size, grade, and estrogen-receptor status, the relative risk reduction shrank to 18%, which was no longer statistically significant, according to Ms. Marshall of the University of California, Irvine.
The California Teachers Study is an ongoing epidemiologic study involving 133,479 female teachers and administrators. Ms. Marshall reported on 2,783 postmenopausal participants diagnosed with breast cancer during 1995-2005. Their mean age at diagnosis was 68 years.
During a mean 5 years of follow-up, 13% of the breast cancer patients died of any cause, and 5.7% died of breast cancer. The breast cancer mortality rate was 9% in HT never-users, 6% in women who had used estrogen-only HT, and 4% in those who took estrogen-progestin. Statistical adjustment for potential confounders was necessary because HT users were as a group leaner, got more exercise, had fewer comorbidities, and their tumors were smaller, lower grade, and less aggressive.
This was the first study ever to adjust for a full range of tumor characteristics, including estrogen-receptor status, Ms. Marshall said.
HT is known to increase breast cancer risk. Ms. Marshall speculated that HT may sensitize the tumors to hormones, making them more responsive to treatment involving hormonal deprivation.
“Use of these hormones appears to be a benefit in terms of protecting against risk of cancer death,” she observed. “This may allow women who have used hormones and who are worried about future breast cancer risk—or even their prognosis if they currently have cancer—to breathe a little easier.”
But Dr. Susan Love, who wasn't involved in the study, had a different take on the results.
“HT causes more cancers; it's just that they're, quote, 'good' cancers. But those 'good' cancers still need surgery, radiation, aromatase inhibitors, maybe chemotherapy. So I think, as a woman, there is no such thing as a 'good' cancer if it's in you. You don't know it's a good cancer until you die at 95 of a stroke,” observed Dr. Love of the University of California, Los Angeles, and president of the Dr. Susan Love Research Foundation.
Moreover, it's controversial whether breast cancer in women who have used HT is associated with improved survival. It was reported elsewhere at the San Antonio meeting that 5-year mortality in roughly 2,000 breast cancer patients in the Women's Health Initiative Observational Study was virtually identical, regardless of whether they had used estrogen-progestin HT or were HT never-users.
'Use of these hormones appears to be a benefit in terms of protecting against risk of cancer death.' MS. MARSHALL