Women with early-stage, HER2-positive breast cancer who are unable to use trastuzumab may benefit from adjuvant lapatinib treatment, suggest phase III trial findings published in Lancet Oncology.
Although adjuvant lapatinib treatment did not significantly improve disease-free survival in the intention-to-treat population of 3147 women with HER2-positive early breast cancer who had received adjuvant chemotherapy but not trastuzumab, it was effective in the 79% of women whose primary tumor was confirmed as HER2 positive by central fluorescence in situ hybridization.
These women had a significantly lower rate of locoregional or distant recurrence, contralateral breast cancer, other tumors, or all-cause death without another cancer event following lapatinib treatment, compared with placebo.
During a follow up of 47.4 months, disease-free survival events occurred in 13% of the 1571 HER2-positive women randomly assigned to receive lapatinib and in 17% of the 1576 women randomly assigned to receive placebo.
This gave a nonsignificant hazard ratio (HR) of 0.83, report Paul Goss (Massachusetts General Hospital, Boston, USA) and co-workers. However, the rate of disease-free survival events in women with confirmed HER2-positive breast cancer was 13% among women taking lapatinib versus 17% among those taking placebo, which gave a significant HR of 0.82.
When the researchers compared efficacy data for women entering the trial within a year of breast cancer surgery and those who began treatment at a later point, they found that lapatinib offered significant benefit for disease-free survival only in patients treated early after surgery.
The overall rate of serious adverse events did not significantly differ between lapatinib- and placebo-treated patients (6 and 5%, respectively), although lapatinib was associated with a higher risk for grade 3-4 diarrhea (6 vs <1%), rash (5 vs <1%), and hepatobiliary disorders (2 vs <1%).
The study was performed between 2006 and 2008 when trastuzumab was either not routinely used or may not have been available due to medical, legal, or financial concerns, explains Per Eystein Lønning (University of Bergen, Norway) in an accompanying commentary.
"Although lapatinib monotherapy might not be more efficacious than trastuzumab, Goss and coworkers' results show that lapatinib given less than 1 year after primary surgery improves disease-free survival," he writes.
"Thus, lapatinib can be offered to the few patients in whom trastuzumab might be contraindicated."
Lønning concludes that it remains to be seen whether lapatinib plus trastuzumab or other anti-HER2 agents improve survival in early breast cancer.
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