Breakthroughs in cancer treatment are often prematurely celebrated, but optimism from recent trials on a relatively new type of therapy may be justified.

Hailed as a “revolution,” scientists have reported “unprecedented” success with a type of personalized treatment called immunotherapy, in which a patient’s own cells are turned into tumor-killing agents. In one trial, where chemotherapy had previously failed, a staggering 94 percent went into remission, the Guardian reports. A paper on the results is pending review.

Announced at the 2016 meeting of the American Association for the Advancement of Science in Washington DC this week, the treatment focuses on components of the immune system called T cells. While these naturally spend their days scouting the body for threats, killing any invaders or cancerous cells they come across, their activity diminishes with some chronic diseases and often they’re not potent or persistent enough to be able to cope with rapidly dividing cancer cells on their own.

But with advances in genetic engineering, scientists realized they could potentially harness and exploit these cells, boosting their innate detective skills so that they specifically target tumors. In this case, researchers headed by Stanley Riddell of the Fred Hutchinson Cancer Research Center engineered T cells to make a receptor that recognizes a molecule called CD19. As this is almost exclusively found on another type of white blood cell called a B cell, this confers the ability to recognize and potently destroy tumors originating from these cells, such as certain lymphomas and leukemias.

After a patient’s T cells are removed, the gene for this synthetic receptor is added in and just two weeks later, the modified cells are ready to be reinfused back into the patient. Importantly, the scientists used a specific subset of T cells that show high regenerative capacity, meaning they linger in the body for extended periods of time after transplantation. This has the added bonus of offering long-term protection against B cell cancers as it gives the immune system a lasting memory that can be called upon should the cancer reappear.

While trials of the therapy have so far only been small, the results have been encouraging and warrant further study. The most impressive results came from a group of 35 patients with a white blood cell cancer called acute lymphoblastic leukemia, in which 94 percent went into remission. And in more than 40 individuals with lymphoma, greater than 50 percent also had their cancer symptoms disappear. Considering other treatments had failed in these patients, and many were only given months to live, these results are even more impressive.

It’s important to note, however, that some patients experienced severe side-effects, including neurological problems and decreases in blood pressure, which the researchers are now working towards reducing. In addition, longer follow-up studies are needed to determine whether the anticancer effects are lasting. But if positive results keep pouring in, and the researchers can successfully tweak this therapy to address other cancers, then we may have a very effective treatment on our hands.