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Lapatinib, trastuzumab may be effective as combination therapy in HER+ breast cancer
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33rd Annual San Antonio Breast Cancer Symposium
SAN ANTONIO — Combination therapy with lapatinib and trastuzumab, when added to paclitaxel, was effective in treating women with HER2-positive breast cancer, according to findings presented here.
Jose Baselga, MD, PhD, professor in the Department of Medicine at Harvard Medical School and chief of Hematology/Oncology and Medicine at Massachusetts General Hospital, said that the combination was more effective than when the drugs were delivered as adjuvant monotherapy.
“Pathological complete response was 53.1% in the combination arm, compared with 29.5% in the trastuzumab monotherapy arm and 24.7% in the lapatinib monotherapy arm,” Baselga said. “Both of these comparisons were statistically significant.”
Baselga noted similar efficacy rates by hormone receptor status.
“In HER-positive patients, the pathological complete response rate was 41.6% in the combination arm, 22.7% in the trastuzumab arm and 16.2% in the lapatinib arm,” he said. “For HER-negative, it was 61.3% for the combination, 36.5% for trastuzumab and 33.8% for lapatinib. These comparisons were also statistically significant.”
Baselga added that there were no major cardiac dysfunctions or toxic deaths during the neoadjuvant phase.
“We have been able to achieve our primary objective,” Baselga said. “The take-home message is that dual anti-HER2 blockade is a valuable concept.”
The aim of the NeoALTTO trial was to determine the efficacy of lapatinib, trastuzumab or a combination of those drugs with paclitaxel when administered as neoadjuvant therapy in patients with HER2-positive breast cancer.
The trial was conducted from January 2008 to December 2009 at 99 centers internationally.
There were 154 patients randomly assigned to lapatinib 1,500 mg/d, 149 patients assigned trastuzumab 4 mg/kg IV loading dose followed by 2 mg/kg IV weekly and 152 patients assigned lapatinib 1,000 mg/d with trastuzumab for 6 weeks.
“After this biological window, patients continued on the same targeted therapy plus weekly paclitaxel 80 mg/m² for a further 12 weeks, until definitive surgery, for a total neoadjuvant therapy duration of 18 weeks,” Baselga said.
After surgery, three cycles of adjuvant fluorouracil, epirubicin and cyclophosphamide and then the same targeted therapy as in the biological window of the neoadjuvant phase were given for an additional 34 weeks. “This provided us with a full 52 weeks of anti-HER2 therapy,” Baselga said.
Pathologic complete response — defined as the absence of invasive cancer in the breast at the time of surgery — was the primary outcome measure. Objective response rate, safety, pathologic node-negative status, rate of conversion to breast conservation, DFS and OS were the secondary endpoints.
On day 15 of the biological therapy window, all patients underwent tumor biopsies for comparative pharmacodynamic analysis.
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