Cancer patients relieved that they can get insurance coverage because of the new healthcare law may be disappointed to learn that some the nation’s best cancer hospitals are off-limits.

An Associated Press survey found examples coast to coast. Seattle Cancer Care Alliance is excluded by five out of eight insurers in Washington state’s insurance exchange. MD Anderson Cancer Center says it’s in less than half of the plans in the Houston area. Memorial Sloan-Kettering is included by two of nine insurers in New York City and has out-of-network agreements with two more.

Doctors and administrators say they’re concerned. So are some state insurance regulators.

In all, only four of 19 nationally recognized comprehensive cancer centers that responded to AP’s survey said patients have access through all the insurance companies in their state exchange.

Not too long ago, insurance companies would have been vying to offer access to renowned cancer centers, said Dan Mendelson, CEO of the market research firm Avalere Health. Now the focus is on costs.

“This is a marked deterioration of access to the premier cancer centers for people who are signing up for these plans,” Mendelson said.

Those patients may not be able get the most advanced treatment, including clinical trials of new medications.

And there’s another problem: It’s not easy for consumers shopping online in the new insurance markets to tell whether top-level institutions are included in a plan. That takes additional digging by the people applying.

“The challenges of this are going to become evident … as cancer cases start to arrive,” Norman Hubbard, executive vice president of Seattle Cancer Care Alliance, said.

Advocates for cancer patients are in a quandary.

Before President Barack Obama’s healthcare law, a cancer diagnosis could make you uninsurable. Now, insurers can’t turn away people with health problems or charge them more. Lifetime dollar limits on policies, once a financial trapdoor for cancer patients, are also banned.

“Patients may have fewer choices of doctors and hospitals in some exchange plans than others … but the rules for such plans go a long way toward remedying the most severe problems that existed for decades,” said Steve Weiss, spokesman for the American Cancer Society Cancer Action Network.

The new obstacles are more subtle.

To keep premiums low, insurers have designed narrow networks of hospitals and doctors. The government-subsidized private plans on the exchanges typically offer less choice than Medicare or employer plans.

By not including a top cancer center an insurer can cut costs. It may also shield itself from risk, delivering an implicit message to cancer survivors or people with a strong family history of the disease that they should look elsewhere.

For now, the issue seems to be limited to the new insurance exchanges. But it could become a concern for Americans with job-based coverage too if employers turn to narrow networks.

The AP surveyed 23 institutions around the country that are part of the National Comprehensive Cancer Network. Two additional institutions that joined this week were not included in the survey.

Cancer network members are leading hospitals that combine the latest clinical research and knowledge with a multidisciplinary approach to patient care. They say that patients in their care have better-than-average survival rates. The unique role of cancer centers is recognized under Medicare. Several are exempt from its hospital payment system, instituted to control costs.

The AP asked the centers how many insurance companies in their state’s exchange included them as a network provider.

Of the 19 that responded, four reported access through all insurers: the Kimmel Comprehensive Cancer Center at Johns Hopkins in Baltimore; Fox Chase Cancer Center in Philadelphia; Duke Cancer Institute in Durham, N.C.; and Vanderbilt-Ingram Cancer Center in Nashville, Tenn. One caveat: Some insurers did not include these cancer centers on certain low-cost plans.

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 healthcare,” 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.

“We are worried about the potential to have these Humana exchange members seek treatment and have no other option,” Zenger said.

Humana spokesman Tom Noland said patients can have access to Huntsman for complex procedures, on a case-by-case basis.

Some state insurance regulators see a problem.

“I want insurers to be able to innovate and come up with new product designs,” said Mike Kreidler, insurance commissioner for Washington state. “At the same time, there is a requirement for regulators like myself to be vigilant to make sure there aren’t unreasonable compromises.”

The Obama administration says it has notified insurers that their networks will get closer scrutiny for next year in the 36 states served by the federal exchange. Cancer care will be a priority, it says.

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Associated Press writers Sheila Burke in Nashville, Tenn., Kim Chandler in Montgomery, Ala., Emery Dalesio in Raleigh, N.C., Jeff Karoub in Detroit, Brady McCombs in Salt Lake City, Christine Scalora in Lincoln, Neb., and Christopher Weber in Los Angeles contributed to this report.