The August 9, 2022 edition of the National Cancer Institute’s Cancer Currents blog announced the findings of the clinical trial KEYNOTE-355 that examined the benefits of using the immunotherapy drug pembrolizumab (Keytruda) in conjunction with chemotherapy in treating advanced triple-negative breast cancer (TNBC).
The results, published in the New England Journal of Medicine (Cortes et al., 2022), revealed that pembrolizumab in conjunction with chemotherapy was effective in extending the lives of TNBC patients with advanced disease as compared to chemotherapy alone, and the difference was striking. Those who received the drug lived a median of 23 months compared to 16.1 months for the chemo-only group.
Of course, cancer differs among patients and not all TNBC tumors are the same. The life-prolonging benefits of pembrolizumab were limited to those patients with PD-L1 scores of at least 10; PD-L1 is an immune checkpoint protein, and the score denotes the level of this protein found in cancer tumor cells.
And it’s important to note that while the drug extended life expectancy, it was not yet a cure, which is what we’re all still waiting for.
So there are asterisks associated with these findings, which might be disappointing for those with advanced cancers of this type. But the researchers stressed that this is a very promising outcome.
Consider the advances that have been made. TNBC used to be treated with untargeted therapies, kind of like throwing everything you’ve got at the tumor and hoping that something “sticks”. On the other hand, pembrolizumab is a targeted therapy for this specific subset of TNBC, and that makes a huge difference.
There has been a push to address the complexities of TNBC and large strides have been made in understanding what makes it tick. New therapies are being approved and they are making researches optimistic about eventually being able to cure the disease.
As an example, in April 2021, the FDA approved the use of sacituzumab govitecan (Trodelvy) for the treatment of certain types of TNBC (after conditional approval had been granted in April 2020). As noted in the May 12, 2021 edition of the Cancer Currents blog, sacituzumab is comprised of an “antibody coupled to a more potent form of the chemotherapy drug irinotecan (Camptosar). The antibody binds to breast cancer cells, delivering the chemotherapy directly to those cells.”
Notably, patients receiving sacituzumab lived a median of 11.8 months longer compared to 6.9 months for those patients receiving the chemotherapy alone. Positive results were also obtained for patients with brain metastases, where the cancer has spread to the brain, who tend to have worse outcomes when treated only with chemotherapy.
There is still so much more to learn. Cancer is a puzzle and researchers have known for some time that the pieces do not yet fit together cleanly. But each one of these advances brings us more effective treatments for TNBC, addressing more specific targets on the tumors. Lifespans are increasing and for many, cancer is taking the form of a chronic disease, not a death sentence.
Cancer Currents Blogs
Sacituzumab Govitecan Approved for Metastatic Triple-Negative Breast Cancer, Cancer Currents, May 28, 2020: https://www.cancer.gov/news-events/cancer-currents-blog/2020/fda-sacituzumab-govitecan-triple-negative-breast-cancer
Sacituzumab Govitecan Earns Full Approval for Triple-Negative Breast Cancer, Cancer Currents, May 12, 2021: https://www.cancer.gov/news-events/cancer-currents-blog/2021/sacituzumab-govitecan-tnbc-regular-approval
Pembrolizumab Improves Survival in Advanced Triple-Negative Breast Cancer, Cancer Currents, August 9, 2022: https://www.cancer.gov/news-events/cancer-currents-blog/2022/pembrolizumab-triple-negative-breast-cancer-improves-survival
KEYNOTE-355 Clinical Trial
(as of this posting, the full article is not yet available to non-subscribers)
Cortes et al. (2022) Pembrolizumab plus Chemotherapy in Advanced Triple-Negative Breast Cancer. New Engl J Med, 387, 217-226. 10.1056/NEJMoa2202809