Stem Cell Transplants Pose Long-Term Cancer Risk

Cancer patients treated with hematopoietic stem cell transplants (HSCTs) have a significant long-term risk for developing a second cancer, especially if they were older at the time of transplant or were treated with stem cells from a female donor, a new study has found.

The study revealed that within 10 years of an allogeneic HSCT, the relative risk of a second, solid cancer is almost twice that of the general population. Furthermore, this cancer risk almost quadruples for those patients who were over 40 at the time of transplant or for patients who received stem cells from a female donor. The study was conducted by Genevieve Gallagher, M.D., and Donna L. Forrest, M.D., from the University of British Columbia (Vancouver, Canada and the BC Cancer Agency (also in Vancouver). The findings were published in the online November 27, 2006, issue of Cancer.

Myeloablative, allogeneic HSCT is an effective standard therapy for specific life-threatening diseases such as leukemia or myelodysplastic syndrome, for which blood cell lineages are abnormal. Destroying the patient's own unhealthy stem cells in the bone marrow and replacing them with a compatible donor's stem cells offers the chance of cure for a disease that otherwise has a high mortality rate with non-transplant therapies. It is also associated with a number of short-term side effects.

Drs. Gallagher and Forrest reviewed the medical records of 926 patients treated with myeloablative stem cell transplants over an 18-year period. They found that at their institution the 10-year incidence of second cancers in these patients was 3.1%. When non-melanoma skin cancer and carcinoma in situ of the cervix were excluded, the incidence was 2.3%, which was 1.85 times that of the general population. The median time to diagnosis was almost seven years after transplant. The most commonly reported second cancers were cancers of the skin, lung, oral cavity, and colon.

Furthermore, the data showed that the risk more than tripled for patients who received their transplant when they were over 40 years of age. Also, patients who received stem cells from a female donor had almost quadrupled the risk of a second solid cancer, a risk that further increased when the patient was male. The researchers are uncertain as to the cause.

"Since the risk of developing a solid neoplasm post-allogeneic transplantation continues to increase with time,” suggest the authors, "extended follow-up will be needed to more fully assess the incidence and risk factors for their development.”