A week before Anissa Ayala turned 16 she was diagnosed with myelogenous leukemia, a particularly aggressive form of the disease. Her only hope was a bone marrow transplant, but no one in her immediate family, including her brother, was a match. Unless a donor could be found — a 1 in 20,000 chance — the young woman who had just celebrated her “sweet 16th” had just a few years left to live.

Anissa was told she had only a couple of years to live. But now she has been cancer free for 20 years thanks to her sister’s donated cells.

Anissa’s family turned to the National Marrow Donor Program. No match was found.

Her parents then made a daring decision. They conceived a baby in hopes that the child might be a match — a lifesaver — for their daughter.

"It was a crazy idea,” Anissa later recalled to People magazine. “My mother was 42, my father had a vasectomy and the odds for a match were less than 25 percent.”

Despite great odds, the Ayala family welcomed a baby girl and she was a perfect match. The later cell transplant was a success; Anissa’s sister saved her life.

Today, 20 years later, Anissa is still free of cancer. Her sister, Marissa, is now 21 and in her third year of college. And the sisters work together to support and promote a variety of cancer-related causes.