Hormone replacement therapy (HRT) has been associated with increased risk of breast cancer and denser breast tissue, which makes it harder to detect breast tumors on mammograms. In contrast, new research in the September 2002 Archives of Surgery points to some possible benefits of HRT for women who are diagnosed with breast cancer. Among women who developed breast cancer, those taking HRT were actually more likely to have their breast cancer detected via mammogram than those not taking HRT. And , women taking HRT had a better six-year survival rate than women not taking HRT.

About the Study

Researchers at Oregon Health Sciences University (OHSU) in Oregon and Akron General Medical Center in Ohio reviewed the medical records of all 292 postmenopausal women diagnosed with breast cancer at OHSU between March 1994 and January 2002. One hundred forty-four of these women had taken HRT before or at the time of diagnosis, and 148 had never taken HRT.

The researchers reviewed the following information in the women’s medical records:

  • Age at diagnosis
  • Method of breast cancer detection - mammogram versus palpation (feeling the tumor during physical examination of the breasts)
  • Tumor size
  • Stage of cancer (how advanced it was at the time of diagnosis)
  • Frequency of mammograms

After following each woman for an average of two years from diagnosis, the researchers compared the method of cancer detection and survival rate of HRT users with nonusers.

The Findings

Among the 144 HRT users, breast cancer was detected by mammography in 84 women and by palpation in 60 women. In contrast, among the 148 nonusers, breast cancer was detected by mammography in 63 women and by palpation in 85 women. Surprisingly, these results suggest that detection via mammography is actually higher in HRT users than in nonusers, even though HRT users did not have mammograms any more often than nonusers. Breast tumors detected via mammography are generally smaller and less advanced than those that are large enough to be detected on physical exam.

Overall, women with tumors detected by mammography had a 94% six-year survival rate compared with 78% among those with tumors detected by palpation. But for HRT users with tumors detected by mammography, the six-year breast cancer survival rate was 100% compared with a survival rate of 87% for nonusers whose tumors were detected by mammography. Among women whose tumors were detected by palpation, survival rates were similar in both groups (about 76% to 79%).

Although these results suggest that women taking HRT who get breast cancer are more likely to survive than nonusers of HRT, the study has its limitations. This study focused on how breast cancer was detected among users and nonusers of HRT, as well as the survival rates in these groups. The study did not, however, account for genetic, lifestyle, environmental, or other hormonal factors that may contribute to the development of a breast tumor, the speed of tumor growth, or how aggressively it spreads. Furthermore, while the study suggested that HRT is associated with earlier detection of tumors via mammography and better survival odds, it did not establish a causal relationship between HRT use and these apparent benefits. Other factors may be responsible for the association, such as closer monitoring by physicians in the HRT group. Finally, the researchers did not differentiate between use of estrogen-only hormone therapy and estrogen-progestin therapy.

How Does This Affect You?

These findings are the latest addition to the contradictory mountain of research on the safety and effectiveness of HRT. In May 2002, researchers halted the Women’s Health Initiative (WHI) study of estrogen-progestin HRT in women with an intact uterus, because the risks of breast cancer, heart attack, and stroke appeared to outweigh the benefits of HRT—reduced risk of osteoporosis and colorectal cancer. This finding flew in the face of conventional thinking that HRT reduces risk of heart disease and stroke. On the other hand, the finding supported the conventional thinking that HRT might increase breast cancer risk. Now, this latest study suggests that HRT may actually increase the chances that a woman’s breast cancer will be detected early and improve her chances of survival. But it’s important to remember that everyone in this study had breast cancer, so the findings tell us nothing about risk of developing breast cancer.

Should you start taking HRT to improve your chances of survival in the event that you do get breast cancer? Absolutely not! It’s still not clear exactly how HRT affects breast cancer risk and the progression of existing breast cancer. In addition, the long-term use of estrogen-progestin HRT for disease prevention is being re-evaluated in light of the multiple adverse events in the WHI study. And don’t forget that estrogen-only (ERT), which is given only to women who’ve had a hysterectomy, must be evaluated separately from estrogen-progestin HRT, which is given to women who’ve not had their uteruses removed.

If you’re taking HRT for the relief of unpleasant menopausal symptoms, such as hot flashes, insomnia, and vaginal dryness, talk with your doctor about your personal risks and benefits of continuing to take HRT.