The operation - the first of its kind involving an unrelated donor - was a success, allowing Mark to live to 24.

The remaining 70 percent must rely on the generosity of an unrelated donor to save their lives.

A transplant from an unrelated donor is more likely to cause problems.

It can take 4 months or longer to find a match from an unrelated donor.

So, he said: "A number of centers did limited trials with living unrelated donors.

About a year ago, he arranged for a bone marrow transplant from an unrelated donor.

As of 2006, more than 7,000 transplants from unrelated donors have been conducted on patients worldwide.

It established the future use of unrelated donors to patients, so far for over 10,000 people.

From matched unrelated donors 91% survived over 100 days.

A nationwide search for an unrelated donor found none.