Immunotherapy’s promise as a cancer therapy is undeniable, yet current treatments only work for some types of cancers. What’s more, it works in only about 20% of patients. But if the results of a new study translate into viable treatments, those statistics may soon change.

When cancer strikes, our immune systems produce T-cells that recognize neoantigens—molecules on the surface of tumor cells—and attack anything in sight that carries them. Drugs that target specific mutations can boost this response, but the surface of cancer cells can vary greatly, even within the same tumor. While drugs might be able to eliminate some harmful cells, they’re not going to catch all of them. The hit-and-miss nature of immunotherapy has been vexing to both cancer researchers and clinicians, and it often leaves patients with remnants of the tumors they had hoped to eliminate.

But in a study published yesterday in the journal Science, Sergio Quezada of University College London and Charles Swanton of the Crick Institute report that, in 150 lung cancer cases, patients had better survival rates if their tumors had many older neoantigens which are the result of so-called trunk mutations that occur early in a tumor’s existence. Because these types of neoantigens are more prevalent than newer neoantigens, they are prioritized by the immune system. It’s a discovery that could help them improve treatments and increase cancer patients’ longevity.

Here’s Ed Yong, reporting for The Atlantic: