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Immunotherapy trials shift breast cancer research closer to ‘Holy Grail’
Immunotherapy is an area that has been a Holy Grail, if you will, in the field of breast cancer.
We have long wondered whether the immune system could be harnessed to fight breast cancer cells.
As we have learned more about how the immune system is controlled, there have been clear innovations in therapy that have made a big difference in melanoma, a type of cancer that naturally stimulates the immune system to a greater extent than breast cancer does.
Debu Tripathy
The PD-1/PD-L1 signaling system is meant to dampen the immune system so it does not become overactive. However, in the case of cancer, we want to block these “checkpoints” at pathways to make the immune system as active as it can be against breast cancer.
One of the key drugs that blocks PD-1, pembrolizumab (Keytruda, Merck), already has been approved in melanoma. A study testing this drug in breast cancer was reported at the San Antonio Breast Cancer Symposium (Nanda R. Abstract #S1-09).
The study included patients with triple-negative breast cancers, one of the hardest types of cancers to treat. These are cancers that do not make the hormone receptor or the HER-2 receptor, and our only current treatment is chemotherapy. But, it is also is a type of cancer that has more mutations. The cell proteins are altered more and it tends to stimulate the immune system more than other types of breast cancer, so this is a perfect setting in which to test these drugs.
The results of a very early study that included patients with advanced triple-negative breast cancer — many of whom had received multiple lines of chemotherapy — were presented, and about one-fifth of the patients responded. That is not a dramatic impact, but it is a start.
We are very encouraged by this because we believe we can build on this as we understand more about the immune system, develop better drugs and, perhaps, better ways to select patients who are most likely to respond. Also, it is possible that the immune system can be overwhelmed by a large number of cancer cells that you might see in someone with advanced breast cancer, so it may be in early-stage breast cancer where the attempt to lower the risk for recurrence may be more successful.
Those kinds of trials are being designed, and going forward, I think we are going to hear much more about the immune system and other drugs that can affect it.
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Debu Tripathy, MD, is chair of breast medical oncology at The University of Texas MD Anderson Cancer Center. He also is a HemOnc Today Editorial Board member. He can be reached at The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030.
Disclosure: Tripathy reports no relevant financial disclosures.