Traditionally, blood cancers like leukemia have been difficult to treat, especially in patients over 50. A host of complications make the chances of a successful marrow or stem-cell transplant unlikely, and the prognosis is typically gloomy. But doctors appear to have found a new way to introduce healthy cells into patients suffering from blood cancers.

There are three major forms of blood cancer -- lymphoma, leukemia and multiple myeloma. Lymphomas account for over half of all new cases, while leukemia accounts for a further 28 per cent. The cancers occur when there is abnormal cell growth in either the bone marrow or the lymphatic tissues. Blood cancers alter the way the body manufactures blood, and affects our overall immunity from other diseases.

Thirty years ago, patients were 50 per cent less likely to survive from these cancers. Recent advances in chemotherapy and radiation treatments have increased survival rates. But no modern advance can match the potential impact of the recent breakthrough announced by doctors at Stanford University.

There are two key requirements when it comes to bone marrow or stem cell transplants. The first is effectively killing as many cancerous cells in the blood cell manufacturing part of the body -- the bone marrow -- as possible. The second is training the recipient's body to accept new cells from their donors. Often, a recipient's body will battle the new cells, killing them off before they can successfully assimilate -- a condition called graft-versus-host disease. A donor and a host's cells living harmoniously, or as clinicians put it, a 'blended' life, is the field's ultimate aim. Usually, this requires strong anti-rejection drugs.