PEOPLE WITH A RARE soft tissue cancer can receive immunotherapy for more than two years without long-term side effects, according to a study presented April 18 at the American Association for Cancer Research (AACR) Annual Meeting 2026 in San Diego. (The AACR publishes Cancer Today.)

Alveolar soft part sarcoma (ASPS) develops in soft tissues like fat, muscles and nerves. Fewer than 100 people in the U.S. each year are diagnosed with this slow-growing cancer, which primarily impacts people ages 15 to 35. Some patients undergo surgery to remove the cancer. But not all cases can be treated surgically, and because the disease does not respond to chemotherapy, people who cannot undergo surgery have limited treatment options.

In December 2022, the Food and Drug Administration approved the immune checkpoint inhibitor Tecentriq (atezolizumab) for people ages 2 and older with unresectable or metastatic ASPS. The approval was based on results of a phase II clinical trial involving 52 people with ASPS who received Tecentriq. During a median follow-up of 13.2 months, one person’s cancer disappeared, 18 had their tumors shrink, and 28 had no disease progression. At the time of the analysis, people who responded to Tecentriq had a median response duration of just more than two years.

As participants continued to have extended responses, researchers wondered if it was safe for them to continue receiving Tecentriq. Some oncologists recommend that people stop taking immune checkpoint inhibitors after two years since long-term use of these drugs can cause side effects, such as joint inflammation, thyroid problems and secondary cancers.

“For some patients, the antitumor response is a slow, ongoing process, and the best time to stop therapy is not clear,” Alice P. Chen, the study’s lead author and the head of the Developmental Therapeutics Clinic at the National Cancer Institute, told Cancer Today via email.

Researchers analyzed data for 17 people who participated in the clinical trial that led to Tecentriq’s approval and had received the drug for more than two years. Five of those patients also took the targeted therapy drug Avastin (bevacizumab) after their disease progressed while on Tecentriq.

The study, which was simultaneously published in the Journal of Clinical Oncology, found participants experienced no life-threatening side effects or secondary cancers, and none stopped treatment because of side effects. “I was pleasantly surprised and happy that these young patients had the opportunity to make independent choices regarding [taking a] drug holiday or continuing treatment,” Chen said. Researchers noted patients did not experience the long-term side effects seen in people who take immunotherapy for long periods, which may be due to the biology of ASPS or because the patients were young, with a median age of 29.

Of the 17 participants, three reported moderate-to-severe treatment-related side effects that did not require hospitalization. One person had elevated levels of an enzyme called aspartate aminotransferase, which may indicate liver damage. Another patient reported itchy skin, while a third had high blood pressure and high levels of protein in their urine, which may indicate kidney damage. Oncologists addressed these side effects by either lowering the treatment dose or prescribing additional medications.

Researchers said the results are encouraging for people with ASPS, particularly those who face a potentially lengthy treatment period. “These results provide information for patients and their oncologist regarding the options for managing treatment at the two-year mark,” Chen said.

Thomas Celona is a senior editor at Cancer Today.