The types of breast tumors that occur after combination hormone replacement therapy in women going through menopause and in post-menopausal women tend to have a better prognosis than those that occur after estrogen-only replacement therapy, Swedish researchers report.
A team at Malmo University Hospital conducted a study involving 12,583 peri- or post-menopausal women whose medical records were linked to national cancer registries. Of the group, 513 had a history of breast cancer prior to enrollment.
During an average of 4.5 years of follow-up, 332 cases of breast cancer were diagnosed, lead investigator Dr. Signe Borgquist and colleagues report in the International Journal of Cancer.
Tumor samples from 283 breast cancers were analyzed for tumor type, grade, estrogen and progesterone receptor status, expression of tumor suppressor genes and other factors.
Among the 2,369 current users of hormone replacement therapy, 1,347 used combined therapy and 984 used estrogen-only therapy; 38 women reported using progestin-only therapy. The incidence of breast cancer was higher in combination hormone replacement users than in non-users, and the estrogen replacement only users did not have a significantly increased risk of breast cancer.
The risk profile of breast cancers developing after combination hormone replacement therapy was more favorable than tumors that occurred in women who received estrogen replacement therapy alone.
Specifically, combination therapy was associated with more grade 1 tumors and more tumors that divided slowly than tumors that recurred after estrogen-only hormone replacement therapy.
Borgquist and colleagues conclude, “These findings correspond well with the image of combination hormone replacement therapy as related to tumors with a favorable prognosis.”
“To date,” they add, “no other study has reported on the association between combination hormone replacement therapy and cell cycle regulators.”