Stony Brook University said Tuesday that Southampton Hospital has officially joined the Stony Brook Medicine health system, after a process that has lasted nearly five years.

The hospital has been renamed Stony Brook Southampton Hospital.

Stony Brook Medicine and the 125-bed hospital announced a letter of intent to merge back in October 2012. The deal required multiple state regulatory approvals.

Stony Brook Southampton Hospital expects to construct a new hospital on Stony Brook University’s Southampton campus. The new facility, which could take up as much as 14 of the campus’s 88 acres, would replace its existing hospital at 240 Meeting House Lane in Southampton.

Stony Brook Southampton Hospital didn’t say how much it needs to raise in order to make the move.

“I’m optimistic this will happen in a reasonable amount of time,” said Samuel L. Stanley, the president at Stony Brook University, who added the move would be paid for privately.

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Separately, Stony Brook also plans to open the Phillips Family Cancer Center on County Road 39 in Southampton by the end of next year.

“When you look at cancer care, people want it close to them,” Stanley said. “At the same time, it needs to be the best care, and we will be able to provide this.”

Other health systems are also expanding cancer care in Long Island communities. For example, Northwell Health opened its first cancer care center in Suffolk County last year. And Memorial Sloan Kettering Cancer Center in Manhattan officially expanded its Commack clinic last year.

MSK has also started work on a $140 million, 140,000-square-foot outpatient treatment and research building on the southwest corner of the Nassau Coliseum property in Uniondale. That facility is expected to open in late 2019.