Two centers have special circumstances. The best known is St. Jude's Children's Research Hospital in Memphis, Tenn. Treatment there is free as long as children have a referral.
For the remaining 13, the gaps are evident.
In Buffalo, N.Y., Roswell Park Cancer Institute is included by five of seven insurers in its region. But statewide, the picture is much different: Roswell Park is not included by 11 of 16 insurers. Dr. Willie Underwood, associate professor of surgical oncology at the teaching hospital, says that's a problem.
"Overall, when you look at the Affordable Care Act, it improves access to cancer care," Underwood said. "When it comes down to the exchanges, there are some concerns that we have. That is not being critical, that is being intelligent. There are some things we should talk about ... before they start becoming a problem."
Melanie Lapidus, vice president for managed care at Barnes-Jewish Hospital in St. Louis, home to Siteman Cancer Center, said she doesn't think patients realize the exchanges offer a more restrictive kind of private insurance.
Lapidus cited Anthem Blue Cross and Blue Shield, which includes Siteman in many of its plans outside the Missouri exchange, but none within the exchange.
"We have had many people say to us, 'I picked Anthem because you guys are always in their products, and I assumed you would be in their exchange products,'" Lapidus said. "It's still hard to tell who is in network and who is not."
In a statement, Anthem said its network was based on research involving thousands of consumers and businesses. "What we learned was that people are willing to make trade-offs in order to have access to affordable health care," the company said. "Our provider networks reflect this."
Huntsman Cancer Institute in Salt Lake City is included by five of six Utah insurers, but Mark Zenger, who manages the center's negotiations with insurance companies, said he's concerned about getting left out by Humana, a major carrier.