New Alpha Radiation Therapy Shows Promise for Hard-to-Treat Melanoma

A therapy that delivers targeted alpha radiation directly to melanoma cells shows effectiveness in mice with minimal side effects, potentially offering a powerful option for patients with metastatic skin cancer, according to a new study.

Researchers from several Japanese institutions, led by Hiroyuki Suzuki, M.D., of Chiba University, developed a novel treatment that uses the body's own targeting system to deliver radiation specifically to melanoma cells. The therapy attaches a radioactive element called astatine-211 to a molecule that naturally seeks out melanoma cells by binding to receptors found on their surface. This approach, described in the European Journal of Nuclear Medicine and Molecular Imaging, allows for precise targeting of cancer cells while sparing healthy tissue.

The use of this treatment demonstrated significant slowing of tumor growth in mice compared with untreated animals, with higher doses providing better results. Importantly, the therapy showed minimal side effects, such as no noticeable weight loss in treated animals.

“If successfully translated into human trials, this therapy may emerge as a viable treatment option for patients with advanced melanoma in the coming years,” Suzuki said in a separate news release. “This could provide new therapeutic opportunities for patients with refractory cancer.”

Alpha radiation therapy uses alpha particles, which are high-energy particles that deliver potent radiation over short distances. The short half-life of astatine-211 — just over 7 hours — means it quickly clears from the body. Unlike traditional radiation or chemotherapies, which affect larger areas and cause broader side effects, alpha radiation therapy precisely targets tumor cells, limiting damage to healthy tissue.

The novel therapy’s use of astatine-211 differs from another emerging therapy called Diffusing Alpha-emitters Radiation Therapy (DaRT), recently approved by the FDA for treating recurrent cutaneous squamous cell carcinoma. DaRT involves implanting tiny seeds impregnated with radium-224 directly into tumors.

As radium decays, it releases short-lived alpha particles that diffuse through the tumor, delivering radiation internally. In contrast, the new astatine-211 therapy relies on targeted peptides that seek cancer cells via receptors rather than implanted seeds.

“We treated the mice with different doses of the compound while monitoring the tumor response, body weight, and survival rates over time. We found a dose-dependent inhibitory effect in a melanoma-bearing mouse model, confirming the effectiveness of our approach,” Suzuki said.

Metastatic melanoma, which occurs when skin cancer spreads to other parts of the body, has an extremely poor prognosis, with a five-year survival rate of 35%, compared with 94% of patients with localized cancer, according to the National Cancer Institute. While recent treatments like immune therapies have improved survival for some patients, many still don't respond to available options.