Hormone replacement therapy (HRT) for breast cancer survivors doesn't appear to increase the risk of cancer recurrence or death, Danish researchers report.
Although HRT has previously been linked to a raised risk of breast cancer's return, those earlier studies referred to oral HRT and not vaginal estrogen cream. The latest study, however, found no increase in the risk of recurrence or death for women getting either type of HRT.
"These findings should be reassuring that the use of HRT is not related to any major risks in the recurrence of breast cancer or risk of death for most women," said lead researcher Dr. Soren Cold, from the department of oncology at Odense University Hospital.
For women taking aromatase inhibitors to lower estrogen levels, there is a small risk of recurrence, but no increased risk of death, he noted.
Cold added that while the study indicates short-term use of HRT for breast cancer patients appears safe, long-term use may be problematic.
In any case, he advises patients to have a detailed discussion with their doctor about using HRT.
"It's something that you'll have to discuss with your doctor because like all other treatments, there are pros and cons," Cold said. "You cannot say it's prohibited, but you have to discuss it strongly with your doctor."
For the study, Cold and his colleagues collected data on nearly 8,500 women diagnosed with early-stage breast cancer between 1997 and 2004. These women received either no hormone treatment or five years of hormone therapy.
Among the women who didn't receive vaginal estrogen therapy or menopausal hormone therapy before a breast cancer diagnosis, 1,957 used vaginal estrogen therapy and 133 used menopausal hormone therapy after their diagnosis.
Over a median of nearly 10 years of follow-up, 16% had a recurrence of breast cancer. In all, 111 patients who had a recurrence had received vaginal estrogen therapy, 16 had received menopausal hormone therapy, and about 1,200 women did not receive either treatment.
The report was published July 20 in the Journal of the National Cancer Institute.
Despite these findings, Dr. Brittany Zimmerman, a medical breast oncologist at Northwell Health Cancer Institute in Lake Success, N.Y., believes breast cancer survivors need to be cautious when using HRT.
The side effects from estrogen deprivation after breast cancer affect many women and can be a major reason for discontinuing breast cancer treatments, such as tamoxifen and aromatase inhibitors, she said.
"As a medical oncologist, one of my main roles is to help patients manage symptoms of these medications to improve quality of life, and help patients remain on their breast cancer-directed therapies," Zimmerman said.
Many strategies are available to manage these side effects, including hormonal and non-hormonal treatments.
"In general, we avoid estrogen-based hormonal therapies for patients with a prior history of breast cancer based on results of prior studies, which show an increased risk of breast cancer recurrence," Zimmerman said.
This study provides an interesting new observation about the use of vaginal estrogen therapy in patients with a history of breast cancer, she said.
"The study found a slightly increased risk of breast cancer recurrence among patients who used vaginal estrogen therapy and were taking aromatase inhibitors," Zimmerman noted.
Earlier studies have shown that vaginal estrogen is generally safe in breast cancer survivors and had very low estrogen absorption into the body, she said.
"I would, however, recommend patients with vaginal symptoms such as vaginal dryness or burning try non-hormonal therapies before using vaginal estrogen therapy," Zimmerman said.
But "this decision should be made after discussion with the patient's breast medical oncologist," she added.
While the new study suggests there is no increased risk of breast cancer recurrence with oral hormonal therapy, several earlier studies have suggested an increased risk, Zimmerman noted.
"I would encourage all patients to discuss the use of hormonal therapy for hot flashes with their medical oncologist and to limit use while further studies are in process," she said.
For more on HRT and breast cancer, head to the American Cancer Society.
SOURCES: Soren Cold, MD, department of oncology, Odense University Hospital, Odense, Denmark; Brittany Zimmerman, MD, medical breast oncologist, Northwell Health Cancer Institute, Lake Success, N.Y.; Journal of the National Cancer Institute, July 20, 2022