San Antonio Breast Cancer Symposium

San Antonio Breast Cancer Symposium

Perspective from Hope S. Rugo, MD, FASCO
Source:

Cortes J, et al. Abstract GS1-02. Presented at: San Antonio Breast Cancer Symposium (virtual meeting); Dec. 7-10, 2021.

Disclosures: Merck funded this study. Cortes reports research funding to his institution from, consultant/advisory roles with, honoraria from, stock or other ownership interests in, or travel, accommodations or expenses from AstraZeneca, Bayer, Celgene, Cellestia Biotech, Clovis Oncology, Daiichi Sankyo, Eisai, Eli Lilly, GlaxoSmithKline, Guardant Health, MedSIR, Merck Sharp & Dohme, Novartis, Pfizer, Roche, Seagen, Servier and other pharmaceutical companies. Please see the abstract for all other researchers’ relevant financial disclosures.
December 09, 2021
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Data confirm efficacy of pembrolizumab regimen for certain breast cancer subgroups

Perspective from Hope S. Rugo, MD, FASCO
Source:

Cortes J, et al. Abstract GS1-02. Presented at: San Antonio Breast Cancer Symposium (virtual meeting); Dec. 7-10, 2021.

Disclosures: Merck funded this study. Cortes reports research funding to his institution from, consultant/advisory roles with, honoraria from, stock or other ownership interests in, or travel, accommodations or expenses from AstraZeneca, Bayer, Celgene, Cellestia Biotech, Clovis Oncology, Daiichi Sankyo, Eisai, Eli Lilly, GlaxoSmithKline, Guardant Health, MedSIR, Merck Sharp & Dohme, Novartis, Pfizer, Roche, Seagen, Servier and other pharmaceutical companies. Please see the abstract for all other researchers’ relevant financial disclosures.
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The addition of pembrolizumab to first-line chemotherapy conferred clinically meaningful benefit to patients with inoperable or metastatic triple-negative breast cancer, according to results presented at San Antonio Breast Cancer Symposium.

A final analysis of the randomized phase 3 KEYNOTE-355 trial showed a PD-L1 combined positive score (CPS) of 10 or higher is “a reasonable cutoff” to identify the patient population most likely to derive benefit from the combination, researchers concluded.

“Several clinical trials have shown activity when combining pembrolizumab with chemotherapy among patients with triple-negative metastatic breast cancer,” Javier Cortes, MD, PhD, head of the breast cancer program at IOB Institute of Oncology in Spain, said during a presentation. “KEYNOTE-355 has shown that pembrolizumab plus chemotherapy resulted in a statistically significant improvement in PFS and OS compared with chemotherapy alone in the frontline setting in tumors that expressed PD-L1 and a CPS of 10 or higher.”

As Healio previously reported, part two of the phase 3 KEYNOTE-355 trial included 847 patients (median age, 53 years; 68% white) with previously untreated, locally recurrent inoperable or metastatic disease whose tumors expressed PD-L1.

Javier Cortes, MD, PhD
Javier Cortes

Researchers randomly assigned 566 women to 200 mg pembrolizumab (Keytruda, Merck) every 3 weeks plus investigator’s choice of chemotherapy, including nab-paclitaxel (Abraxane, Celgene), paclitaxel or gemcitabine/carboplatin, for up to 35 administrations. The other 281 patients received chemotherapy alone.

Median follow-up was 44 months in both groups.

In the final analysis, Cortes and colleagues assessed outcomes in subgroups of patients with PD-L1 CPS of less than 1, 1 to 9, 10 to 19, and 20 or higher.

Baseline characteristics appeared well-balanced between treatment groups, Cortes said.

Results showed the improvement in median OS conferred by pembrolizumab increased as PD-L1 expression increased: CPS less than 1 (16.2 months vs. 14.7 months; HR = 0.97; 95% CI, 0.72-1.32); CPS 1 to 9 (13.9 months vs. 15.5 months; HR = 1.09; 95% CI, 0.85-1.4); CPS 10 to 19 (20.3 months vs. 17.6 months; HR = 0.71; 95% CI, 0.46-1.09); and CPS 20 or higher (24 months vs. 15.6 months; HR = 0.72; 95% CI, 0.51-1.01).

The improvement in median PFS with pembrolizumab also increased with higher PD-L1 expression: CPS less than 1 (6.3 months vs. 6.2 months; HR = 1.09; 95% CI, 0.78-1.52); CPS 1 to 9 (5.7 months vs. 5.6 months; HR = 0.85; 95% CI, 0.65-1.11); CPS 10 to 19 (9.9 months vs. 7.6 months; HR = 0.7; 95% CI, 0.44-1.09); and CPS 20 or higher (9.2 months vs. 5.4 months; HR = 0.62; 95% CI, 0.44-0.88).

Researchers reported no new safety signals.

“These results provide further support for pembrolizumab in combination with chemotherapy as a good treatment option and perhaps a new standard of care treatment regimen for certain patients with locally recurrent unresectable or metastatic triple-negative breast cancer whose tumors express PD-L1 with a CPS of 10 or higher,” Cortes said. “We still have so many unanswered questions, and future studies may help us better define the best group of patients who will achieve optimal benefit from the addition of immune checkpoint inhibitors not only in the metastatic disease setting but also in the early-stage setting.”