In addition to the physical and mental toll her disease takes on her, it's also very difficult for her financially. Though she says she's fortunate to have COBRA insurance, her out-of-pocket costs are steep.

"COBRA is really expensive, and I still have out-of-pocket costs at the beginning of the year. Plus, every time I go in for a test or to see the doctor, there's a $30 co-pay," said Gaines, who is 56. "Last year, my out-of-pocket cost was $10,000."

Gaines knows she isn't alone, that there are many other cancer patients who are uninsured and have to foot enormous bills on their own.

Those costs, according to a new study by the National Cancer Institute (NCI), are expected to soar to $158 billion by the year 2020.

Researchers led by Angela Mariotto, a statistician in the NCI's Division of Cancer Control and Population Sciences in Bethesda, Md., analyzed available data on the number of new cancer cases, survival rates after diagnosis and costs of care, and projected a staggering 27 percent increase in the cost of cancer care over the next decade.

The most expensive cancers are breast cancer, colon cancer, lymphoma, lung cancer and prostate cancer.

"This number is a bit higher than we expected," said Mariotto.

She said the data are estimates that assume the number of new cancer cases remains the same over time, treatment-related costs remain the same and the population ages at the rate projected by the U.S. Census Bureau.

The NCI study also estimated that if costs in the early and late stages of cancer treatment rise by two percent a year, which is consistent with current trends, the projected cost of cancer could be as high as $173 billion a year.

Experts said the increase has a number of causes, including increased cancer survival, a growing number of older Americans, treatment advances and the desire to offer and receive the best and most care.

One of the main reasons for the skyrocketing cancer price tag is the growing number of Americans who are getting older.