Researchers found that omitting cyclophosphamide from a regimen of epirubicin and paclitaxel increased the likelihood of an early return of menses, and there was a trend toward improved disease-free survival.
The phase 3 SPECTRUM trial involved 521 women with estrogen receptor–positive, HER2-negative breast cancer who had undergone definitive surgery at one of eight institutions in China. The average age of the patients was 34 years.
Cyclophosphamide is a standard component of adjuvant chemotherapy, but it’s strongly associated with premature ovarian failure and infertility.
“For the first time, we demonstrate that a cyclophosphamide-free regimen [can] increase the rate of menses recovery without compromising survival,” said the researchers, led by Ke-Da Yu, MD, PhD, of the Fudan University Shanghai (China) Cancer Center.
They also reported that, among the women who tried to conceive at a later date, there was a higher pregnancy success rate among those who did not take cyclophosphamide.
“Our findings can be extrapolated to patients with other subtypes of breast cancer, such as triple-negative or HER2-enriched, because the effect of paclitaxel and cyclophosphamide on menstrual resumption is not subtype specific,” the investigators commented.
The results were published online in the Journal of the National Cancer Institute.
This is the first prospective trial specifically designed to find an adjuvant breast cancer regimen less toxic to the ovaries. The “investigators ... should be applauded,” wrote Matteo Lambertini, MD, PhD, of the University of Genova (Italy), and Ann Partridge, MD, of the Dana-Farber Cancer Institute in Boston, in an accompanying editorial.
Although promising, there are a few caveats, the editorialists wrote. In a past trial of doxorubicin and docetaxel in lieu of a cyclophosphamide regimen, disease outcomes were inferior. There is also a question as to whether the SPECTRUM results apply to non-Asian women.
The editorialists also noted that enrollment in this trial ended in 2016, before it was recommended that ovarian suppression be used in conjunction with adjuvant chemotherapy to prevent premature menopause.
“[It’s] notable that the absolute benefit in reducing [premature ovarian insufficiency] rates with the use of a cyclophosphamide-free regimen is similar to the effect demonstrated with the administration of a gonadotropin-releasing hormone agonist during cyclophosphamide-based chemotherapy,” they commented. It’s possible that combining the two approaches might have an additive effect, but for now the possibility remains unknown.
In addition, the SPECTRUM trial predates the widespread use of genetic testing to guide treatment, the editorialists pointed out.
“Therefore, caution should be taken in adopting wholesale such regimens,” Dr. Lambertini and Dr. Partridge said.
Switch to paclitaxel
The research team was inspired by previous reports that swapping out cyclophosphamide for paclitaxel did not reduce adjuvant efficacy in the general breast cancer population.
The SPECTRUM trial randomly assigned 260 women to receive a cyclophosphamide-free regimen of epirubicin (75 mg/m2) and paclitaxel (175 mg/m2) every 3 weeks for four cycles followed by weekly paclitaxel (80 mg/m2) for 12 weeks.
Another 261 women were randomly assigned to receive cyclophosphamide (600 mg/m2) and epirubicin (75 mg/m2) every 3 weeks for four cycles followed by weekly paclitaxel (80 mg/m2) for 12 weeks. These patients constituted the control group.
A year after completing chemotherapy, 63.1% of the cyclophosphamide-free arm versus 48.3% of the control group, had resumed menses, defined as having two consecutive menstrual cycles or one cycle but with premenopausal levels of estradiol and follicle-stimulating hormone (P < .001).
Another caveat of the study is that assessments of women who resumed menses were conducted at the 1-year point; rates may have been higher in the cyclophosphamide arm had the investigators conducted the assessments at 2 years, the editorialists said.
The 5-year disease-free survival was 84.7% in the cyclophosphamide-free arm versus 78.3% in the control group, an absolute difference of 14.8% (P = .07).
Patients with node-positive disease appeared to benefit the most from cyclophosphamide sparing.
There were no statistically significant differences in overall or distant disease-free survival.