Background

Improving outcomes for patients with human epidermal growth factor 2-positive (HER2+) central nervous system (CNS) metastases remains an unmet clinical need. This trial evaluated a novel combination of everolimus, lapatinib and capecitabine for this disease.

Methods

Patients with trastuzumab-pretreated, HER2+ breast cancer brain metastasis without prior therapy with a mammalian target of rapamycin (mTOR) inhibitor were eligible. Patients received lapatinib and everolimus daily (continuously) and capecitabine twice daily (d1-14) in 21-d cycles. The primary endpoint was the 12-week CNS objective response rate (ORR). Secondary endpoints included safety, progression-free survival (PFS), overall survival (OS), best CNS ORR and extra-CNS ORR.

Results

A total of 19 participants were enrolled and treated with ⩾1 dose of the study drug. The median age was 58.5 years, the median number of therapies for metastatic breast cancer was 2.5 (0-11). Pretrial, 74% of participants had received prior lapatinib, capecitabine or both. A total of 63% had received previous CNS radiation or surgical resection and CNS radiation. The maximum tolerated doses were lapatinib at 1000 mg, everolimus at 10 mg, and capecitabine at 1000 mg/m². Phase II proceeded with capecitabine at 750 mg/m² due to better tolerability. The most common grade 3/4 adverse events were mucositis (16%), diarrhea, fatigue, and hypokalemia (11% each). Of 11 participants evaluable for 12-week CNS ORR, 3 (27%) had partial response and 7 (64%) had stable disease. The best CNS ORR in eligible participants was 28% (5/18). The median PFS and OS were 6.2 and 24.2 months, respectively.

Conclusions

This novel triplet combination of lapatinib, everolimus, and capecitabine is well tolerated and yielded a 27% response rate in the CNS at 12 weeks in heavily pretreated participants. Larger studies are warranted to further evaluate this regimen.

Trial registration

ClinicalTrials.gov: NCT01783756. Registered 05 February 2013, https://clinicaltrials.gov/ct2/show/NCT01783756.

In this multicenter, open-label, randomized phase II investigator-sponsored neoadjuvant trial with funding provided by Sanofi and GlaxoSmithKline (TRIO-US B07, Clinical Trials NCT00769470), participants with early-stage HER2-positive breast cancer (N = 128) were recruited from 13 United States oncology centers throughout the Translational Research in Oncology network. Participants were randomized to receive trastuzumab (T; N = 34), lapatinib (L; N = 36), or both (TL; N = 58) as HER2-targeted therapy, with each participant given one cycle of this designated anti-HER2 therapy alone followed by six cycles of standard combination chemotherapy with the same anti-HER2 therapy. The primary objective was to estimate the rate of pathologic complete response (pCR) at the time of surgery in each of the three arms. In the intent-to-treat population, we observed similar pCR rates between T (47%, 95% confidence interval [CI] 30-65%) and TL (52%, 95% CI 38-65%), and a lower pCR rate with L (25%, 95% CI 13-43%). In the T arm, 100% of participants completed all protocol-specified treatment prior to surgery, as compared to 69% in the L arm and 74% in the TL arm. Tumor or tumor bed tissue was collected whenever possible pre-treatment (N = 110), after one cycle of HER2-targeted therapy alone (N = 89), and at time of surgery (N = 59). Higher-level amplification of HER2 and hormone receptor (HR)-negative status were associated with a higher pCR rate. Large shifts in the tumor, immune, and stromal gene expression occurred after one cycle of HER2-targeted therapy. In contrast to pCR rates, the L-containing arms exhibited greater proliferation reduction than T at this timepoint. Immune expression signatures increased in all arms after one cycle of HER2-targeted therapy, decreasing again by the time of surgery. Our results inform approaches to early assessment of sensitivity to anti-HER2 therapy and shed light on the role of the immune microenvironment in response to HER2-targeted agents.