Children with a certain type of blood cancer do better following a transplant than chemotherapy, say doctors.
The cells needed for transplant can be harvested from the blood
The Italian team compared the therapies in children with high-risk acute lymphoblastic leukaemia (ALL).
Those who received blood stem cell transplants from a well-matched donor, such as a sibling, were far less likely to relapse than the other children.
The Lancet work suggests the sickest ALL children should be offered transplants whenever possible.
Dr Adriana Balduzzi and colleagues at the University degli Studi di Milano Bicocca followed the outcomes of 357 children with high-risk ALL.
All of the children were somewhat resistant to standard treatment, meaning it had failed to get their leukaemia under adequate control, called remission.
The researchers checked the children's relatives to see if any were a suitable donor.
For 77 of the children, a suitable donor was found and these children received the blood stem cell transplants.
The remaining 280 children were given chemotherapy instead.
Over five years, the death rate was similar among both groups.
However, significantly more children in the transplant group had a disease free life with no relapse than those in the chemotherapy group - 57% compared to 41%, respectively.
The benefits of a transplant over chemotherapy were particularly marked in the children at highest risk of relapse and was obvious after about 18 months of the treatment.
The researchers said their work provided good evidence to guide doctors making treatment decisions.
Ken Campbell, clinical information officer at Leukaemia Research, said: "Previously there has not been a good quality objective study on this strategy.
"The results strongly suggest that children with high-risk ALL are more likely to be cured by a stem cell transplant that chemotherapy."
He pointed out that the findings only applied to a minority of children with leukaemia.
About 85% of children with leukaemia have ALL, and acute myeloid leukaemia (AML) accounts for most of the rest.
Of those with ALL, about 8% will have high-risk ALL. In the study, a suitable donor was found for only a fifth of the children with high-risk ALL.
"For this small proportion of children there is a clear benefit from having a transplant early," he said.