By medical standards, Margaret Divine was doing everything right to reduce her risk of colorectal cancer.

She made sure to get a colonoscopy every three to five years, which is generally recommended for people age 50 and older. But when she was tested in April, doctors detected a precancerous polyp. If it was left untreated it would have developed into colorectal cancer.

Since Mrs. Divine belonged to Anne Arundel County Department of Health's LifeScreen program, she was able to get the surgery for free. Out of pocket, those services would cost at least $1,200, officials said.

"The main thing that scared me was the word...