Women with HER2-positive early breast cancer achieved similar disease-free survival when assigned to 6 months of adjuvant trastuzumab as compared with a 12-month duration, and had fewer cardiac side effects, according to the results of the phase III PERSEPHONE trial (abstract 506) presented at a press conference ahead of the 2018 American Society of Clinical Oncology (ASCO) Annual Meeting, to be held June 1–5 in Chicago.
Helena Earl, MBBS, PhD, professor of clinical cancer medicine at the University of Cambridge in the United Kingdom, who presented the results, called them exciting, adding that they are “confident this will mark the first step toward reduction in treatment duration for any woman with HER2-positive breast cancer.”
About 15 out of every 100 women diagnosed with breast cancer have HER2-positive disease. Use of trastuzumab has significantly improved outcomes for these women, Earl said.
Results from pivotal registration trials established a 12-month duration of adjuvant trastuzumab as standard of care for women with HER2-positive early-stage disease. However, no trial to date has demonstrated noninferiority of a shorter duration of adjuvant treatment.
The PERSEPHONE trial tested a 6-month and 12-month duration of trastuzumab in 4,088 women enrolled at 152 UK sites. Women were randomly assigned 1:1 to 6 months or 12 months of trastuzumab and were also treated with chemotherapy: anthracycline-based, taxane-based, or a combination of both.
With a median follow-up of more than 5 years, the 4-year disease-free survival rate was 89.4% for women assigned to 6 months of treatment and 89.8% for women assigned to a 12-month duration—a difference of only 0.4%, Earl noted.
Cardiac events occurred twice as commonly in women assigned to 12 months of trastuzumab as compared with 6 months. Trastuzumab was stopped in 8% of women assigned to the 12-month duration compared with only 4% assigned to the 6-month duration (P < .0001). Cardiac data showed that cardiac function does recover on a 12-month regimen, but does so more quickly in patients assigned to only 6 months (P = .02).
ASCO President Bruce Johnson, MD, said that this was an important study that will help patients to live longer and live better. The noninferiority of the shorter duration should also have an effect on cost, he said.
“We think this is important for the 12% of women with early-stage HER2-positive breast cancer,” Johnson said.