Tucatinib in Combination with Trastuzumab and Capecitabine in HER2-Positive Metastatic Breast Cancer - Episode 3

Updated Results from HER2CLIMB and Tucatinib Use in Patient Subgroups

Combination therapy with tucatinib, trastuzumab, and capecitabine shows efficacy in all patient populations studied.

Sara A. Hurvitz, MD: In the HER2CLIMB study, the protocol specified that another analysis of overall survival would be done approximately 2 years after the last patient was randomized. These updated survival data were presented at ASCO [the American Society of Clinical Oncology annual meeting] this year. Interestingly, the overall survival differences, in spite of the fact that patients crossed over from the placebo arm to the tucatinib arm, continued to favor patients who were originally assigned to the tucatinib arm. The hazard ratio was 0.73, which is statistically significant. The median overall survival for patients in the tucatinib arm was 24.7 months, compared to 19.2 months in the placebo arm. So there was about a 5.5-month benefit with the use of tucatinib in this particular clinical trial. A nice separation of the curves is easily seen on the Kaplan-Meier analysis. Prespecified subgroups, an exploratory analysis, was also presented, and interestingly, the survival improvements appeared to be seen with tucatinib regardless of patient age, race, hormone receptor status, and in patients who have baseline brain metastases, you’re seeing a significant improvement in overall survival, with a trend toward one in patients without brain metastases. There wasn’t a subgroup that wouldn’t tend to benefit from the use of tucatinib.

A lot has been made about choosing agents that are particularly active if a patient has visceral metastasis and the need for getting a dramatic response. I think it’s important that the investigators did an exploratory analysis looking at outcomes for patients based on whether they have visceral metastasis. Over 450 patients had visceral metastases on this clinical trial. The hazard ratio was 0.70 for them, which was statistically significant at 0.004. The median overall survival was about 21.6 months for those treated with tucatinib vs 16.9 months for those not. For those without visceral metastases, again, a smaller number of patients, the trend was toward the favor of tucatinib, with a hazard ratio 0.80. This wasn’t statistically significant. This wouldn’t discourage me from using tucatinib in patients without visceral metastases. However, it gives me reassurance that using tucatinib in patients with visceral metastasis is a safe thing to do.

Transcript Edited for Clarity