Bone marrow transplants can save lives. The researchers -- who included Donna Forrest, MD, of the British Columbia Cancer Agency -- aren't arguing against those transplants.
Instead, Forrest's team says scientists need to do more work to understand whether cancer risk rises after bone marrow transplantation.
The study appears in Cancer's online "Early View" edition.
Data came from 926 patients who got bone marrow transplants at Vancouver General Hospital, the British Columbia Cancer Agency, or the British Columbia Children's Hospital between 1985 and 2003.
The patients were 12-65 years old (average age: 39). Most were adults; only 20 were younger than 18.
Most patients had leukemia. Their bone marrow transplants came from their siblings or unrelated donors.
The patients got yearly checkups that included physical exams and blood tests.
The patients were followed for up to 10 years. During that time, the vast majority of patients didn't get a second cancer.
However, 28 patients developed another cancer. Those cancers developed seven years, on average, after bone marrow transplantation.
The data don't prove that those cancers were tied to the bone marrow transplants. Doctors often can't explain exactly why cancers develop.
Patients who got bone marrow transplants were 85% more likely to develop a second solid cancer than the general public in British Columbia, the researchers note.
That figure doesn't include the chance of getting nonmelanoma skin cancer or carcinoma in situ of the cervix (the earliest stage of cervical cancer).
Further analysis showed that patients were more likely to develop another cancer if they were at least 40 years old when they got their bone marrow transplant.
Cancer risk rises with age. The researchers don't know whether the higher cancer risk in patients aged 40 and older was due to aging or other factors.
The study also shows that patients were more likely to get another cancer if their bone marrow donor was a woman.
That finding was "unexpected" and its explanation is "uncertain," the researchers write.
They call for "extended follow-up" to gauge the chances of getting cancer after bone marrow transplants.
SOURCES: Gallagher, G. Cancer, Nov. 27, 2006; online "Early View" edition. News release, John Wiley & Sons Inc.
By Miranda Hitti
Reviewed by Louise Chang