San Antonio Breast Cancer Symposium

San Antonio Breast Cancer Symposium

December 09, 2016
3 min read

Certain menopausal symptoms associated with nonadherence to breast cancer therapy

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SAN ANTONIO — Women who experienced certain menopausal symptoms appeared significantly less likely to adhere to long-term breast cancer therapy, according to data from the IBIS-I study presented at San Antonio Breast Cancer Symposium.

Headache, nausea and vomiting were among the symptoms associated with nonadherence.

“To date, there have been nine randomized trials testing the effectiveness of selective estrogen receptor modulators in the primary prevention setting,” Samuel G. Smith, PhD, Cancer Research U.K. postdoctoral fellow and university academic fellow at University of Leeds in the United Kingdom, said during a press conference. “Data from IBIS-I and other trials indicate that adherence to tamoxifen treatment reduces risk of breast cancer by at least 30%, and that this effect seems to last for at least 20 years.”

However, tamoxifen has been associated with elevated risk for thromboembolic events, endometrial cancer and menopausal side effects.

Smith and colleagues examined the effect of menopausal symptoms on tamoxifen adherence — defined as at least 4.5 years on therapy — in women included in the IBIS-I trial, designed to show whether 5 years of tamoxifen treatment conferred long-term breast cancer preventive benefits to women at elevated risk for the disease.

The current analysis included 3,987 women aged 35 to 70 years. Of this group, 1,987 were assigned tamoxifen and 2,000 were assigned placebo.

Exclusion criteria included death or invasive cancer diagnosis, serious thrombotic event or receipt of prophylactic mastectomy.

The two study groups were comparable with regard to median age (tamoxifen, 49.3 years; placebo, 49.2 years), BMI (25.7 vs. 25.9), family history of breast cancer (one relative, 39.6% vs. 39.1%; two or more relatives, 60.4% vs. 60.9%) and Tyrer-Cuzick 10-year risk score (median, 5.7% in each group).

Menopausal symptoms — including nausea, vomiting, headache, hot flashes and gynecologic symptoms — experienced prior to trial entry or within the first 6 months of treatment were characterized as mild, moderate or severe.

Results showed women assigned placebo were significantly more likely to adhere to treatment for 4.5 years (71.5% vs. 62.1%; P < .0001). Researchers also reported significantly longer mean time on study in the placebo group (4.3 years vs. 3.9 years; P < .0001).

Overall, after 6 months, a small percentage of women reported experiencing nausea/vomiting (5%) or headache (7%). The majority of each were characterized as mild.

Nearly one-third (31.5%) of women experienced hot flashes, more than half of which were mild. About one in five women (20.9%) experienced gynecologic symptoms, most of which were mild.

Analysis showed significantly lower treatment adherence rates among women who experienced nausea/vomiting (53.7% vs. 71.3%; P < .001) and headaches (58.6% vs. 71.3%; P = .01) compared with women who did not experience those symptoms. Hot flashes and gynecological symptoms also appeared associated with lower rates of treatment compliance, but the differences did not reach statistical significance.

Researchers analyzed the association between symptoms and treatment adherence stratified by trial arm. Heterogeneity tests revealed the effects of symptoms on adherence were comparable between trial arms, Smith said.

“Interventions are needed to manage menopausal symptoms,” Smith said. “Drop-out rates were fastest during the first 12 months of therapy, indicating that this is an optimal time in which to deliver such interventions.

“Addressing medication concerns prior to initiating therapy may encourage more realistic expectations ... and prevent them from misattributing symptoms that were naturally occurring to their particular therapy,” Smith added. “Cognitive behavioral therapy has been shown to be effective in the adjuvant setting in terms of managing menopausal symptoms. It would be interesting to test this hypothesis in the primary prevention setting.” – by Jennifer Southall


Smith SG, et al. Abstract S5-03. Presented at: San Antonio Breast Cancer Symposium; Dec. 6-10, 2016; San Antonio.

Disclosure: Cancer Research UK funded this study. Smith reports no relevant financial disclosures. Please see the abstract for a list of all other researchers’ relevant financial disclosures.