The new findings also show that women with low baseline anti-Müllerian hormone (AMH) of less than 10 pg/mL do not benefit from chemotherapy. In fact, AMH levels were a better predictor of chemotherapy benefit than self-reported premenopausal status, age, and other hormone levels.
“We may be overtreating some of our patients” with invasive breast cancer and low AMH levels, Kevin Kalinsky, MD, of the Winship Cancer Institute of Emory University, Atlanta, said in a presentation at the annual meeting of the American Society of Clinical Oncology (ASCO).
The potential implication of the study is that clinicians may be able to stop giving chemotherapy to a subset of breast cancer patients who will not benefit from it, he said in the presentation.
New Analysis Singles Out AMH Levels
In a new analysis of data from the RxPONDER trial, Dr. Kalinsky shared data from 1,016 patients who were younger than 55 years of age and self-reported as premenopausal.
The original RxPONDER trial (also known as SWOG S1007) was a randomized, phase 3 trial designed to evaluate the benefit of endocrine therapy (ET) alone vs. ET plus chemotherapy in patients with hormone receptor positive and human epidermal growth factor receptor 2 negative (HR+/HER2-) invasive breast cancer and low recurrence scores (25 or less with genomic testing by Oncotype DX), Dr. Kalinsky said in his presentation.
The researchers found no improvement in invasive disease-free survival (IDFS) with the addition of chemotherapy to ET overall, but significant IDFS improvement occurred with added chemotherapy to ET in the subgroup of self-reported premenopausal women (hazard ratio 0.60).
To better identify the impact of menopausal status on patients who would benefit or not benefit from chemotherapy in the new analysis, the researchers assessed baseline serum samples of serum estradiol, progesterone, follicular stimulating hormone(FSH), luteinizing hormone, AMH, and inhibin B.
The primary outcomes were associations of these markers (continuous and dichotomized) with IDFS and distant relapse-free survival with prognosis and prediction of chemotherapy benefit, based on Cox regression analysis.
Of the six markers analyzed, only AMH showed an association with chemotherapy benefits. “AMH is more stable and reliable during the menstrual cycle” compared to other hormones such as FSH and estradiol. Also, AMH levels ≥ 10 pg/mL are considered a standard cutoff to define normal ovarian reserve, Dr. Kalinsky said in his presentation.
A total of 209 patients (21%) had low AMH (less than 10 pg/mL) and were considered postmenopausal, and 806 (79%) were considered premenopausal, with AMH levels of 10 pg/mL or higher.
Chemotherapy plus ET was significantly more beneficial than ET alone in the premenopausal patients with AMH levels ≥ 10 pg/mL (hazard ratio 0.48), Dr. Kalinsky said. By contrast, no chemotherapy benefit was seen in the patients deemed postmenopausal, with low AMH levels (HR 1.21).
In the patients with AMH of 10 pg/mL or higher, the absolute 5-year IDFS benefit of chemotherapy was 7.8%, compared to no notable difference for those with low AMH levels.
Similarly, 5-year DRFS with chemotherapy in patients with AMH of 10 pg/mL or higher was 4.4% (HR 0.41), with no benefit for those with low AMH (HR 1.50).
The findings were limited by the post hoc design and lack of longitudinal data, Dr. Kalinsky said.
During the question-and-answer session, Dr. Kalinsky said that he hoped the data could be incorporated into a clinical model “to further refine patients who need chemotherapy or don’t.” The results suggest that the reproductive hormone AMH can be used to identify premenopausal women with HR+/HER2- invasive breast cancer and intermediate risk based on oncotype scores who would likely benefit from chemotherapy, while those with lower AMH who could forgo it, Dr. Kalinsky concluded.