Immunotherapy has revolutionized melanoma treatment, with some patients achieving durable remissions that would have been unthinkable 15 years ago. But as these powerful immune-boosting drugs expand to treat cancers across more than 10 organ systems, doctors are racing to understand and prevent the serious complications they can cause.

How Have Immunotherapy Drugs Changed Melanoma Survival?

The transformation has been dramatic. When Douglas Johnson, M.D., started his fellowship in hematology-oncology at Vanderbilt in 2011, the first checkpoint inhibitor had just been approved for melanoma. "I remember seeing patients during my fellowship who had been treated for melanoma in the first trials in the mid-2000s and were still alive more than five years later at that point," Johnson explained. "The historical survival for metastatic melanoma had been about six to nine months on average, and we were seeing these amazing responses, with tumors melting away and patients living for years after their original treatment".

Today, five checkpoint inhibitors are on the market, targeting different molecular "brakes" that cancer cells use to hide from the immune system. These drugs work by releasing those brakes, allowing the body's immune cells to attack cancer. For melanoma, anti-PD1 and anti-PDL1 drugs achieve response rates of about 45 percent when used alone, and nearly 60 percent when combined with ipilimumab, a drug targeting a different checkpoint called CTLA4.

What Serious Side Effects Can Immunotherapy Cause?

The challenge is that unleashing the immune system against cancer can also cause it to attack healthy tissues. Javid Moslehi, M.D., assistant professor of Medicine and director of the Cardio-Oncology Program at Vanderbilt-Ingram Cancer Center, emphasized the stakes: "Even one death is too many. We are working hard with our oncology colleagues to find ways to give these drugs more safely".

The side effects vary widely in type and severity. When checkpoint inhibitors are combined, the risks increase substantially. Common complications include:

• Colitis: Inflammation of the colon, the most frequently reported side effect in melanoma patients receiving combination therapy
• Pneumonitis: Inflammation of the lungs that can develop during or after treatment
• Endocrine dysfunction: Damage to hormone-producing glands, affecting metabolism and other vital functions
• Liver inflammation: Elevated liver enzymes and hepatitis-like symptoms requiring close monitoring
• Cardiac and neurological inflammation: Rare but potentially life-threatening inflammation of the heart or nervous system

"Almost any organ can be affected by inflammation," Johnson noted. These complications can emerge weeks or even months into treatment, requiring oncologists and other specialists to work together to manage them.

How Are Doctors Working to Prevent These Complications?

Vanderbilt investigators and their colleagues are taking a systematic approach to improve safety. They are carefully monitoring patients during and after therapy, creating databases of patient information, and collecting blood and tissue samples to search for biomarkers that predict who will respond to treatment and who is at risk for toxicity.

"These drugs have now shown activity in cancers that arise in over 10 different organ systems, so they're going to be used in many more patients going forward," Johnson explained. "That means we will see more of the side effects, and we would really like to prevent them if we can".

One promising approach combines immunotherapy with cancer vaccines. A recent study presented at the American Society of Clinical Oncology annual meeting found that intismeran, a therapeutic cancer vaccine, plus pembrolizumab (a checkpoint inhibitor) significantly improved outcomes in patients with high-risk melanoma. The combination reduced the risk of cancer recurrence by about 49 percent and the risk of distant metastasis by about 59 percent compared with pembrolizumab alone. The vaccine works by stimulating the immune system in a targeted way, potentially enhancing the checkpoint inhibitor's effectiveness while the safety profile remained manageable.

What Does This Mean for Melanoma Patients Today?

The story of Buddy Boane illustrates both the promise and the peril. In 2015, the retired police officer and martial arts instructor discovered a small spot on his heel that he initially thought was a runner's sore. It turned out to be an aggressive melanoma. After surgery removed the tumor and surrounding tissue, new spots appeared, and Boane chose combination immunotherapy as his best option.

The treatment worked initially. After two infusions, the spots began shrinking. But after four infusions, Boane ended up in critical condition in the intensive care unit with severe liver inflammation. His blood work revealed concerning numbers, and he required intensive medical management to survive the complication.

Boane's experience underscores why close monitoring is essential. Patients receiving checkpoint inhibitors need regular blood tests, imaging, and symptom assessments. Any new symptoms, fever, or unusual fatigue should prompt immediate medical evaluation. Oncologists increasingly work with cardiologists, pulmonologists, gastroenterologists, and endocrinologists to catch and manage complications early.

The good news is that when side effects are caught and treated promptly, many patients can continue their cancer treatment successfully. The expanding toolkit of immunotherapy options, including combination approaches with cancer vaccines, offers patients more choices and better chances of long-term survival than ever before. But that progress depends on informed patients and vigilant medical teams working together to balance the life-saving benefits against the real risks.