Immunotherapy, a revolutionary cancer treatment that empowers the immune system to combat malignant cells, has transformed outcomes for numerous cancers once considered untreatable. However, this potent therapy can also trigger severe, persistent side effects as the hyperactive immune system attacks healthy tissues, leaving some patients with lifelong health challenges.
Introduced less than two decades ago, immunotherapy has dramatically improved survival rates for diseases like advanced melanoma, where ten-year survival has increased from less than 5 percent to over half. Similar breakthroughs have been observed in certain lung and kidney cancers, with ongoing research showing promise in other difficult-to-treat tumors.
Despite its successes, the treatment carries significant risks. Patients can develop immune-related adverse events, where their own immune system targets healthy organs. These complications can manifest unpredictably, affecting organs such as the thyroid, lungs, liver, bowel, skin, or heart, and can persist long after treatment concludes.
Kate Harrison, a breast cancer patient, recounted her experience with pembrolizumab, an immunotherapy drug used for triple-negative breast cancer (TNBC). After undergoing chemotherapy and immunotherapy, she experienced severe colitis, an inflammation of the large intestine, and later pneumonitis, an inflammation of the lungs, as her immune system attacked her own body. These side effects necessitated stopping the immunotherapy early and led to prolonged hospitalizations and steroid treatments.
Professor Richard Simcock, chief medical officer at Macmillan Cancer Support, highlighted the unpredictability of immunotherapy toxicity. "We don’t yet have a way of understanding who will be affected, what side effects they may get and, crucially, how long problems may last," he stated, emphasizing the uncertainty patients face.
A large European study involving 545 patients revealed that two-thirds experienced immune-related side effects, with nearly half requiring hospital admissions. The study reported four fatalities, three of which were linked to lung inflammation.
Professor Anna Olsson-Brown, chief executive of the Immuno-Oncology Clinical Network (IOCN), noted that severe or life-threatening toxicity affects a significant portion of patients, ranging from one in five to one in two, depending on the specific treatment. "These toxicities are not a rare complication. They are a routine part of the treatment," she said.
The financial and healthcare system burden of immunotherapy is also substantial. Beyond the drug's list price, which can be nearly £90,000 for a full course, costs are incurred through emergency admissions, specialized drugs, and extended follow-up care. Access to specialist teams that manage these toxicities remains limited.
While immunotherapy is considered a golden age in cancer care, experts emphasize the need for patients to be informed about potential side effects and to advocate for their health. Harrison, despite her challenging experience, stated she would still choose immunotherapy, acknowledging its role in eliminating her cancer while hoping for better management of its long-term consequences.