A groundbreaking study shows that a personalized mRNA vaccine, when combined with immunotherapy, can reduce the risk of melanoma returning by 49% and significantly improve survival rates. After five years of follow-up, nearly 69% of patients receiving the combination therapy remained cancer-free, compared to 49% of those on immunotherapy alone.

How Does This Personalized Vaccine Actually Work?

Unlike the COVID-19 vaccine that everyone received, this melanoma vaccine is custom-made for each patient. Here's the process: after surgeons remove a patient's melanoma tumor, researchers sequence the cancer cells to identify up to 34 unique molecular fingerprints called neoantigens. These are abnormal proteins that only exist on that specific person's cancer cells. Scientists then encode these neoantigens into a messenger RNA (mRNA) vaccine tailored to that individual.

When the vaccine is injected, it trains the body's immune cells, called T cells, to recognize and attack those specific cancer markers. Meanwhile, the immunotherapy drug Keytruda (pembrolizumab) works by removing the "don't attack me" shield that cancer cells use to hide from the immune system. Together, they create a one-two punch: the vaccine teaches the immune system what to look for, and the immunotherapy removes cancer's camouflage.

What Do the Five-Year Results Actually Show?

The study, called KEYNOTE-942, followed 157 melanoma patients in Australia and the United States who had surgery to remove their tumors. Researchers randomly assigned them to receive either the personalized vaccine plus Keytruda, or Keytruda alone. The results were striking:

• Cancer-Free Survival: 68.8% of patients on combination therapy remained cancer-free at five years, versus 49.1% on immunotherapy alone, representing a 49% reduction in recurrence risk
• Overall Survival: 92.2% of the combination therapy group were alive at the five-year mark, compared to 71.3% of the immunotherapy-only group
• Spread Prevention: The combination therapy reduced the risk of cancer spreading to distant parts of the body, such as the lungs, liver, or brain, by 59%

The results were presented at the American Society of Clinical Oncology conference and published in the Journal of Clinical Oncology.

"This is an incredibly interesting trial because the approach is just so unique. It is a personalized immunotherapy strategy tailored to each patient's tumor," said Dr. Janice Mehnert, a melanoma specialist and researcher at NYU Langone Health.

Dr. Janice Mehnert, Professor in the Department of Medicine at NYU Grossman School of Medicine

Why Does Prevention Matter More Than Treatment After Recurrence?

Melanoma is the deadliest form of skin cancer, with approximately 112,000 cases diagnosed annually in the United States and about 8,500 deaths. While early detection and surgery can be effective, predicting when melanoma will return is difficult. Sometimes recurrence can be treated with surgery or radiation, but when cancer spreads to the lungs, liver, or brain, treatment becomes far more challenging.

That's why researchers focused on prevention rather than waiting for cancer to come back. By using the vaccine early in a patient's disease course, doctors aim to harness the immune system's power before any hidden cancer cells can grow and spread.

"We're trying to harness the power of the immune system early in a patient's disease course to optimize their outcomes," explained Dr. Mehnert.

Dr. Janice Mehnert, Director of Melanoma Medical Oncology at Perlmutter Cancer Center

What About Side Effects and Safety?

In the trial, side effects were mild and manageable. Patients reported fatigue, minor pain at injection sites, and chills. No serious safety concerns emerged during the five-year follow-up period, making the vaccine a well-tolerated addition to standard immunotherapy.

What's Next for This Technology?

The vaccine, called intismeran, was developed by Moderna in collaboration with Merck, the maker of Keytruda. A Phase 3 trial involving nearly 1,000 patients is now underway to confirm these results and test whether the vaccine works as a first-line treatment for melanoma. Researchers are also studying whether mRNA vaccines can prevent recurrence of other cancers, including lung cancer.

Once Phase 3 results are analyzed in the coming months, the goal is to seek FDA approval for the vaccine. For patients like Connie Franciosi, an 80-year-old who participated in the original trial, the results speak for themselves. She remains cancer-free five years after her diagnosis and recently celebrated her 80th birthday, spending her days gardening, volunteering at her local library, and playing golf with friends.

"I am cancer-free. Life is good," said Franciosi, reflecting on her experience in the trial.

Connie Franciosi, Clinical Trial Participant

This personalized vaccine approach represents a significant shift in how doctors think about treating high-risk melanoma. Rather than waiting for cancer to return and then fighting it, this strategy trains the immune system to prevent recurrence from the start.