- Pembrolizumab received accelerated approval by the FDA for locally recurrent unresectable or metastatic triple-negative breast cancer (TNBC).
- Tumors must express the protein PD-L1 using an FDA-approved test.
- Approval was based on the KEYNOTE-355 trial showing that the pembrolizumab+chemo group lived an additional 4.1 months.
Why this matters
- TNBC has the highest mortality among breast cancer subtypes.
- Pembrolizumab is 1 of the first immunotherapies approved for any breast cancer subtype.
- Tumors expressing PD-L1 must have a combined positive score ≥10.
- Pembrolizumab must be given in combination with chemotherapy.
- Pembrolizumab's recommended dose is 200 mg every 3 weeks or 400 mg every 6 weeks before chemotherapy until disease progression or unacceptable toxicity or up to 24 months.
- Chemotherapy must be 1 of 3 regimens: paclitaxel protein-bound, paclitaxel, or gemcitabine by intravenous infusion.
- Highlights of KEYNOTE-355:
- Multicenter, double-blind, randomized, placebo-controlled trial in locally recurrent unresectable or metastatic TNBC not already treated with chemotherapy.
- Primary outcome:
- PFS was 9.7 months in the pembrolizumab+chemo group vs 5.6 months in the placebo+chemo group.
- HR, 0.65 (one-sided P=.0012).
- Most common adverse events (incidence ≥20%) with pembrolizumab+chemo group were fatigue, nausea, diarrhea, constipation, vomiting, alopecia, among others.
- Most common laboratory abnormalities were anemia, leukopenia, neutropenia, among others.