The following article features coverage from the San Antonio Breast Cancer Symposium (SABCS) 2017 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Adding lapatinib to a trastuzumab/taxane regimen was associated with significantly improved event-free survival (EFS) among women with HER2-positive (HER2+) breast cancer, according to findings from the randomized phase 3 CALGB 40601 trial presented at the 2017 San Antonio Breast Cancer Symposium.1

“Overall survival was also increased, but the number of events was very small,” noted coauthor author Ian E. Krop, MD, PhD, of the Dana-Farber Cancer Institute in Boston, Massachusetts.

EFS benefit was primarily seen in patients with Luminal A tumors.

Previous research has shown that trastuzumab and lapatinib are synergistic, potently inhibiting HER2 signaling in preclinical trials, and that the combination is active in both untreated and heavily pretreated HER2+ advanced breast cancer, Dr Krop said.

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Between December 2008 and February 2012, 305 patients with stage II to III HER2+ breast cancer underwent tumor biopsy and were then randomly assigned to receive paclitaxel plus trastuzumab alone (TH) or with lapatinib (THL) for 16 weeks before surgery.

Evaluable EFS and RNA-sequencing gene expression information was available for 265 patients. At a median follow-up of 5.4 years, 39 EFS events were recorded (THL, 7 events; TH, 19 events; TL, 13 events).

EFS was significantly longer in the THL arm than for standard TH (hazard ratio, 0.35; 95% CI: 0.15-0.84; P = .013).

pCR had “quite a marked effect” on EFS, Dr Krop said. “Those who did not achieve pCR had substantial risk of recurrence.”

Patients with HER2-enriched disease who had a pCR had significantly better EFS than those who did not reach pCR (hazard ratio, 0.14; 95% CI: 0.04-0.44; P < .0001).

According to Dr Krop, the data need to be validated and should be treated only as hypothesis-generating at this point. “A better understanding of the clinical and molecular features in HER2+ breast cancer is likely to be key in rationally escalating and de-escalating therapy,” he concluded.

Read more of Cancer Therapy Advisor‘s coverage of the San Antonio Breast Cancer Symposium (SABCS) 2017 meeting by visiting the conference page.

Reference

  1. Krop IE, Hillman D, Polley MY, et al. Invasive disease-free survival and gene expression signatures in CALGB (Alliance) 40601, a randomized phase III neoadjuvant trial of dual HER2-targeting with lapatinib added to chemotherapy plus trastuzumab. Oral presentation at: 2017 San Antonio Breast Cancer Symposium; December 5-9, 2017; San Antonio, TX.