D.C. health officials postponed making a recommendation Thursday on two competing hospital proposals to establish a controversial cancer treatment.

MedStar Georgetown University Hospital and Sibley Memorial Hospital, part of Johns Hopkins Medicine, are both vying to offer proton beam therapy, a cutting-edge radiation treatment that hospital executives say is more precise in targeting tumors and safer for healthy tissue than conventional X-rays.

Sibley is proposing a $130 million facility that would open in 2017, taking up one-third the size of a football field. MedStar Georgetown says its slimmer $32 million center could begin operating next year at its Lombardi Cancer Center. Neither project can move forward without the go-ahead from the D.C. State Health Planning and Development Agency.

Members of an agency advisory committee said Thursday that they wanted more information from the hospitals about cancer screening and treatment programs they have promised in underserved parts of the District, which has some of the highest cancer rates in the country. The screenings and treatments are a condition D.C. officials have asked for as part of the proton approval.

The committee also wants more details about Sibley’s proposed partnerships with three other hospitals — Children’s National Medical Center, Howard University Hospital and United Medical Center — which is a key part of their proton proposal.

Proton centers in the U.S.

The competition between two of the region’s largest hospital systems is part of what critics say is a nationwide medical arms race to invest millions of dollars in technology that has not been proved to be better than cheaper alternatives for some cancers.

Hospital executives and experts generally agree that the treatment has the most potential to benefit children, particularly those with brain and eye tumors. The therapy can be administered at higher doses than conventional radiation and causes fewer long-term side effects.

But they also acknowledge that research has yet to demonstrate that the treatment, which is more expensive than conventional radiation, is better than conventional therapy for other cancers, such as prostate cancer, even though many hospitals want to use proton therapy to treat that disease.

Hospitals using proton technology get higher Medicare reimbursements than those using conventional radiation, studies have shown.

Today, 11 proton facilities operate in the United States, and at least 17 are under construction or in development, including one at the University of Maryland in Baltimore set to open in two years, according to the National Association for Proton Therapy.

A preliminary report by the health planning agency found that both hospitals had demonstrated a need for proton services in the District.

At two public hearings, hospital executives argued over who is best positioned to serve poorer residents, the type of beam technology they planned to use and other issues.

In conventional radiation therapy, X-rays deliver radiation as they enter and exit healthy organs. Proton therapy uses a beam of protons, which are positively charged subatomic particles. Unlike X-rays, which have no mass, protons deliver a very low entrance dose, and when they arrive at their target — the tumor — they deliver the dose and stop. There’s no exit dose, and healthy tissue is spared.

Another advisory council is set to vote on the proposals next month. Its recommendation will go to health planning agency director Amha Selassie, who makes the final decision.