Pembrolizumab May Benefit Selected Patients With Incurable Metastatic Breast Cancer

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Metastatic TN and hormone receptor–positive disease is incurable and new therapy options are badly needed.
Metastatic TN and hormone receptor–positive disease is incurable and new therapy options are badly needed.
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 pembrolizumab to doxorubicin or an aromatase inhibitor (AI) may benefit some patients with triple-negative (TN) or hormone receptor–positive metastatic breast cancer (MBC), according to a poster being presented at the 2017 San Antonio Breast Cancer Symposium.1

Metastatic TN and hormone receptor–positive disease is incurable and new therapy options are badly needed.

For this phase 1/2 trial, researchers assigned patients with PD-L1-positive disease to 1 of 2 cohorts. In the dose-finding Cohort 1, 3 patients with TN MBC received escalating doses of doxorubicin 50 mg or 60 mg concurrently with pembrolizumab 200 mg every 3 weeks for 2 years. In Cohort 2, 20 patients with hormone receptor–positive disease were treated with pembrolizumab 200 mg every 3 weeks along with an AI.

Among patients in Cohort 1 receiving doxorubicin 50 mg, there was 1 partial response (PR), 1 unconfirmed PR, and 1 patient who did not progress for 7 cycles. No dose-limiting toxicities were reported.

Among patients in Cohort 2, researchers observed 1 unconfirmed PR (evaluation ongoing after 3 cycles) and 1 case of stable disease (progressed after 12 cycles), with 3 patients still undergoing treatment. Fourteen patients had disease progression within 4 cycles; 1 patient discontinued treatment because of liver toxicity.

Grade 3 adverse events (AEs) included liver function abnormalities, rash, and lymphocytopenia. Grade 2 AEs included fatigue, cough, ankle edema, insomnia, arthralgia, hypertension, hot flashes, headaches, and rash.

The authors concluded that “[e]arly proliferation of peripheral blood T cell subsets may be a potential on-treatment biomarker to identify the MBC subset that will benefit from the [addition] of pembrolizumab and a full analysis of correlative studies is underway in the TN cohort to better guide effective and efficient cancer immunotherapy.”

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. Somlo G, Yuan Y, Waisman J, et al. Phase I-II trial of pembrolizumab and either doxorubicin (Dox) or an aromatase inhibitor (AI) for triple negative (TN) or hormone receptor positive (HR+) metastatic breast cancer (MBC). Poster presented at: 2017 San Antonio Breast Cancer Symposium (SABCS); December 5-9, 2017; San Antonio, TX.

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