Treatment for thousands of Long Islanders battling cancer at Memorial Sloan Kettering Cancer Center could no longer be covered by UnitedHealthcare by the end of June.

UnitedHealthcare (UHC) and Memorial Sloan Kettering Cancer Center (MSK) are currently in talks for contract negotiations.

Patients received letters from UHC notifying them that MSK could no longer be in-network by July 1, depending on their plan.

Lee Kassler, of Plainview, was shocked to read the letter he received on Saturday.

"This is a matter of life or death,” he said.

Kassler was diagnosed with a rare form of gastric cancer almost three years ago. He gets chemotherapy every two weeks at MSK.

"My caregivers, I consider them part of my extended family,” said Kassler. "They know me, they know what's going on. They have answers to some of my questions before I need to ask."

In a statement to News 12, an MSK spokesperson wrote, "We put patients at the center of everything we do and are working to ensure that they can continue their cancer care without interruption."

A UHC spokesperson told News 12, "We are committed to utilizing the remaining time on our contract to reach an agreement that is affordable for the people and employers we serve while providing continued, uninterrupted network access to MSK."

Kassler, a new grandfather, says he can't imagine battling cancer with another group of caregivers.

"That would make me feel as devastated as hearing the doctor tell me, 'Lee, you have cancer,'” he said.

MSK released a full statement with more details here.

Check with UHC for more specifics on when in-network coverage ends based on the plan.

More details from UHC can be found here.