A pilot program from the Centers for Medicare & Medicaid Services that allows seniors to receive hospice care while continuing curative treatment doesn’t allow enough patients to enroll, according to hospice provider groups.

In a letter to CMS Principal Deputy Administrator and Chief Medical Officer Patrick Conway M.D., the National Hospice and Palliative Care Organization said the pilot was “constructed too narrowly” and managed so closely that not enough patients are able to participate.

The program, which was announced in 2014, pays a select group of hospice providers $400 in Medicare funds per beneficiary per month for palliative services, while also allowing providers to bill Medicare for curative services.

“There has been genuine excitement about the program, and immediate identification of patients who could benefit from the extra support,” wrote NHPCO President and CEO Don Schumacher. “At this time, enrollment is dangerously low. Surely this is not what Congress intended when it authorized this program, nor is it instructive to CMS or policymakers on how they can better coordinate curative and palliative care for individuals with advanced illness and at the end of life.”

The pilot’s 14 requirements for participation, including limits to how long patients have been in Medicare, or whether they were only in the hospital on observation status, are barriers to participation, Schumacher noted.

He recommended CMS’ Innovation Center, which runs the pilot, to revisit its participation criteria and ensure that a “steady pipeline” of patients have the opportunity to test the model.