Young patients with cancer and blood diseases will receive care under one roof at a new children’s hospital in a plan announced Thursday to unify services now provided separately by Kaleida Health and Roswell Park Cancer Institute.

Officials from the two institutions signed a memorandum of understanding that dedicates a floor of a new children’s hospital to Roswell Park’s pediatric hematology-oncology program.

Ground-breaking for the recently renamed John R. Oishei Children’s Hospital, a replacement for the Women & Children’s Hospital campus on Bryant Street, is expected next spring on the downtown Buffalo Niagara Medical Campus.

Roswell Park and Women & Children’s have collaborated in the care of young cancer patients for nearly 40 years and, together, treat more than 80 percent of the children in Western New York with cancer and blood disorders, officials said.

Many of the patients receive specialty services at Roswell Park and complementary care at the children’s hospital. In 2011, this amounted to 618 hospital admissions and more than 5,300 clinic visits.

However, the institutions provide the care at separate facilities, requiring patients, families and staff to work in a system that has been an impediment to providing optimal treatment.

“It’s not the most efficient setup,” said Dr. Martin Brecher, chief of hematology oncology at Women & Children’s and chairman of pediatrics at Roswell Park. “This is a step forward and puts us in the forefront of providing care to these children.”

The $200 million new hospital will go up at the corner of Ellicott and High streets, across from and connected by a walkway to Buffalo General Medical Center. Completion is scheduled for early 2016.

The Kaleida Health hospital system operates the children’s hospital, which plans to submit a certificate of need application today with the New York State Health Department. The state reviews and approves projects and major equipment purchases under the certificate of need process.

Roswell Park anticipates seeking a review for the proposed pediatric hematology-oncology center by the end of the year, officials said.

James R. Kaskie, chief executive officer of Kaleida Health, characterized the plan as another milestone in efforts to encourage collaboration among the key health care providers in the Buffalo area, where for many years the health care landscape was defined by intense competition and fragmented care among hospitals.

“Timing is everything,” Kaskie said. “It shows that when you focus on the right thing – the children – things can happen.”

Similarly, Dr. Donald L. Trump, chief executive officer of the cancer center, talked about the alignment as a “terrific opportunity.”

“Management of cancer is best provided in facilities where hospital inpatient beds and outpatient facilities are in close proximity,” he said.

It is anticipated that Roswell Park, a National Cancer Institute comprehensive cancer center, will hold a long-term lease for the proposed center and will operate it.

Currently, Women & Children’s Hospital provides such services as surgery, anesthesia, intensive care and diagnostic imaging. Roswell Park provides leadership in cancer treatment and such services as radiation therapy, highly specialized diagnostic tests, blood and marrow transplants, and clinical cancer trials.

The proposed center will incorporate inpatient beds, an outpatient clinic, isolation beds for blood and bone marrow transplant/high-dose therapy patients, and infusion facilities for chemotherapy and blood products, all in a protected environment on the top floor of the new hospital.

The consolidation of care at one site will improve services and boost research, doctors said. For instance, bone marrow transplant patients under age 4 – there are about five a year in the region – now must receive treatment elsewhere because of the safety issues surrounding their highly specialized care when split between two sites. That would change in a unified program.

In addition, one pediatric cancer care site could spark research opportunities now impossible because of the impracticality of replicating expensive and complex equipment and services in two places, such as tissue sampling for studies into the genetic sources of cancer.

“The [project] emphasizes that patients and families are the highest priority,” said Dr. Lorna Fitzpatrick, a pediatric oncology-hematology specialist. “The best medicine is practiced in multidisciplinary teams.”

The memorandum of understanding represents a start to what will likely be a complicated process. Among other things, the institutions must arrange funding for the center and solve labor issues. Roswell Park operates as a public-benefit corporation with major support from the state and public employee unions. Kaleida Health is a private, not-for-profit hospital with workers represented by multiple unions.

An official of the Service Employees International Union, which represents workers at Women & Children’s, could not be reached to comment.

Trump said officials at the institutions believe the collaboration will attract more patients, creating a situation that benefits all the players involved in the new center.

The children’s hospital, after lengthy study by its physicians, decided in 2010 in favor of a move to the downtown medical center rather than an attempt to reconstruct its current campus. Physicians see benefits in a smaller, more efficient and modern facility close to an adult hospital on the medical campus.