DURHAM, N.C. — When colorectal cancer goes unchecked, it can spread to different organs of the body. One couple took part in a clinical trial at Duke that may have added precious months or even years to their life together.

David Lassiter has colon cancer. Three years ago, the news from his doctor was like a death sentence.

"The doctor said, 'You've got about six months to live. You won't make it to Christmas.' This was in June," he said.

Lassiter is optimistic by nature.

"If you think you don't have a way to go, it's hard to build up optimism. Somebody else can't really give it to you. But you can find it some place," he said.

Lassiter found optimism with Catherine Burrows.

"She says, 'Well, I guess I'll marry you so I can take care of you. I don't know how often you hear that, but you don't turn that offer down," Lassiter said.

After his first diagnosis, doctors removed the cancerous section of his colon, but the cancer came back and it had spread to the liver and lungs. That's when Lassiter joined a clinical trial for drug therapy that includes Avastin.

The trial was before the Food and Drug Administration approved it for general use. Previous trials showed dramatic results for patients with advanced stage colon cancer, like Lassiter.

"The main idea is that for a weed to grow, it needs roots. For a tumor to grow, it needs a special blood supply," said Duke oncologist Dr. Herman Hurwitz.

Avastin targets the blood supply to stop tumor growth and possibly cause it to shrink. Lassiter is still on the drug therapy -- 60 treatments over 2½ years. He has taken at least 70 trips between Boone and Durham over the 2½-year period.

"All the nurses, we know them by name," Lassiter said.

The therapy seems to be working.

"It's working fine. It's kept it stable. It's not going to go away," Lassiter said.

The Internet is their link to fundraising efforts back home. With others going through the same struggle with cancer, many go it alone. Lassiter said he cannot imagine how.

"I wouldn't have made it without her. I probably wouldn't have tried and I couldn't have made it," he said.

In a previous trial, with Avastin in combination with standard chemotherapy, patients with advanced colorectal cancer survived an average of five months longer than patients who received standard chemotherapy alone.