Checkpoint inhibitor immunotherapy drugs have generated excitement and hope over the past few years, as those taking them have incredibly enabled their own immune systems to attack their cancer cells.
But while the benefit can be miraculous (some have begun referring to these drugs a “revolution” in cancer treatment), their potential side effectswhich oncologists call immune-related adverse events, or "IrAEs"can be difficult to tolerate. About half of patients treated with these drugs will experience rashes, diarrhea, muscle aches, flu-like symptoms, and fatigue.
Read MoreThe condition is marked by high blood glucose levels, resulting from an inability to produce insulin. It requires patients to carefully monitor their blood glucose levels throughout the day and self-administer insulin shots accordingly.
Immunotherapy hasn't been around for all that long, relative to other treatments, so the exact reason why the drugs can cause some patients to develop diabetes is still a mystery.
"We are not yet sure why insulin-dependent diabetes develops following checkpoint inhibition," Dr. Cheryl Selinsky, vice president of Research Operations at the Parker Institute for Cancer Immunotherapy, told SurvivorNet. "But what we do know is that checkpoint inhibitor therapies are designed to release the brakes on the immune system, prompting it to attack tumor cells. In the rare case of cancer immunotherapy patients who develop insulin-dependent diabetes, the body appears to begin attacking the insulin-producing cells of the body in the pancreas following treatment."
The Parker Institute for Cancer Immunotherapy, where Dr. Selinsky works, has just launched an extensive research collaboration in an effort to get to the bottom of the mysterious adverse effect. In addition to figuring out exactly why this happens, the researchers are trying to pinpoint which patients, if any, might be more prone than others to developing diabetes after treatment.
"As part of our extensive research, we will be looking for clues such as biomarkers that would indicate if a person is more likely to develop diabetes as a result of immunotherapy," Dr. Selinsky said. Questions the researchers are hoping to answer include whether the timing or dose of immunotherapy correlates to specific outcomes, and why some patients develop disorders weeks after their treatment, while others may go many months before developing any symptoms at all.
The potential for developing diabetes can seem alarming. It is, after all, an irreversible condition that can be fatal if managed improperly. But because the effect is so rareand the potential benefits of immunotherapy so greatit's probably not worth losing sleep over.
"Only about 1 percent of patients will develop this form of diabetes following checkpoint inhibitor treatment," Dr. Selinsky said. "For most cancer patients, the potential upside of immunotherapy is greater than the risk."
And while it's important to note that that potential upsidethat is, a complete cancer responsehas only been seen in 12 percent of patients, and only 43 percent of patients with cancer are eligible for the drugs to begin with, those numbers are on the rise.
"For the first time, we're getting truly curative therapies in many kinds of diseases," Dr. Jim Allison, 2018 recipient of the Nobel Prize for Physiology or Medicine and Chair of the MD Anderson Cancer Center Department of Immunology, recently told SurvivorNet. "And not just in melanoma but in lung cancer, kidney cancer, bladder cancer, Hodgkin's lymphoma, Merkel cell cancer, head and neck cancer. It goes on and on."
Dr. Geoffrey Oxnard, a thoracic oncologist at Dana-Farber Cancer Institute noted to SurvivorNet, "I have patients where the immune system has cleaned out the cancer, and they remain cancer-free."
That possibility, to many people dealing with difficult cancer diagnoses, can make a one percent chance of having to inject themselves with insulin every day seem like an ok tradeoff.
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