The skyrocketing cost of new cancer treatments is putting advances in fighting the deadly disease out of reach for a growing number of Americans, Reuters and MSNBC.com reported.

Cancer patients are abandoning medical care because the costs are simply too high and medical bills — even among the insured — are unmanageable, studies show.

“There’s a growing awareness that the cost of cancer treatment is unsustainable,” said Dr. Lee Schwartzberg, an oncologist who did a study examining the factors that contributed to patients quitting their oral cancer drugs.

Cancer is one of the most expensive diseases to treat, with costs topping $124 billion in 2010 in the United States, according to the National Cancer Institute. That cost is expected to reach $158 billion by 2020.

“When it’s an expensive drug, we have to have the hard discussion about a very substantial out-of-pocket payment. I ask: ‘Do you want to spend this money for an average improvement of just a few months of life?’ I’m very uncomfortable having those discussions because I want to focus on the patient getting better,” Schwartzberg, medical director of the West Clinic in Memphis, Tenn., said in an interview.

Schwartzberg’s and other cost studies presented at the American Society of Clinical Oncology annual meeting come as U.S. lawmakers battle over ways to reduce the national debt, including cuts in health-care funding.

Until recently, almost all cancer drugs were administered intravenously. Today, about a quarter of them can be given orally, which means fewer visits to the doctor.

But pills are often more expensive, have higher co-payments, and are reimbursed by insurers at lower rates than IV drugs, said Dr. Michael Link, president of the oncologists’ association.

Using a database of pharmacy claims paid by private insurers and Medicare, he found  that those with higher co-payments quit their drugs more often.

Patients with co-payments of more than $500 were four times more likely to abandon treatment than those with co-payments of $100 or less, Schwartzberg said.

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