Ms. St. Pierre also now qualifies for Medicare, the federal health insurance program, because she is disabled, but her husband’s plan remains her primary source of insurance. Medicare would still leave her with significant medical bills if she lost her husband’s coverage because she has no supplemental insurance.

Without the lifetime cap, Ms. St. Pierre says she can now focus on what treatment makes the most sense rather than gamble that the most aggressive care will cure her and allow her to escape the maximum limits on coverage. “It opens up all sorts of options,” she said, including viewing her cancer as a chronic condition that she can afford to treat for many years.

Cancer patients like Ms. St. Pierre who are concerned about running out of coverage often try to tailor their treatments to see if they can avoid hitting their lifetime caps, said Stephen Finan, senior director of policy at the American Cancer Society. “People have to think about what’s their strategy,” he said.

And while Ms. St. Pierre, who has worked with the cancer society, says she knows she is likely to be able to continue to receive some treatment without insurance, she also knows that it is not likely to be the optimal care. The same is true for any patient who runs out of coverage, Mr. Finan said. “You may well continue to get care, but the quality of care is markedly lower,” he said.

The last time Mr. Ell neared the maximum on his parents’ policies, he had only $77,000 in remaining coverage  about a month’s worth of his clotting medicine. He had been able to switch plans offered by his parents’ employers. He works part time and is not eligible for insurance from his employer.

Among employers, the feelings are mixed about whether the limits should be eliminated, said Andrew Webber, who is the president of the National Business Coalition on Health. One of the coalition’s members, the Midwest Business Group on Health, recently conducted a survey of opinions by employers. About a quarter of those surveyed wanted to repeal the new law’s ban on lifetime and annual limits to coverage. While about half wanted to keep the provisions, some employers object on the grounds that they do not want the government to dictate what benefits they offer their workers. “Employers, for so many years, have had so much flexibility to design and change their policies from year to year,” Mr. Webber said, and the new law changes that.