NEW YORK (Reuters Health) – Children who are disease-free 5 years after a cancer diagnosis are still at risk for recurrence for another 20 years or more, new research suggests.

The study involved 12,795 survivors of the most common childhood cancers: leukemia, Hodgkin’s and non-Hodgkin’s lymphoma, neuroblastoma, soft tissue sarcoma, and tumors of the central nervous system, kidney, or bone.

In the Journal of the National Cancer Institute for December 16, Dr. Karen Wasilewski-Masker, from Children’s Healthcare of Atlanta, and co-investigators report a 6% cumulative incidence of recurrence between 5 to 20 years after the original diagnosis. In some cases, recurrence developed up to 29 years later.

“Five-year disease-free survival is often interpreted to mean ‘cure,'” the researchers write. But, they add, their data show that while 5-year disease-free survival will mean “cure” for most children, “there remain survivors among all diagnoses at risk for late recurrence. It is likely impossible to say when an individual survivor is ‘cured.'”

Data for the report came from the Childhood Cancer Survivor Study, the largest cohort of adult survivors of childhood cancer under direct surveillance in the U.S.

Patients were diagnosed between 1970 and 1986. Their median age was 8.3 years at diagnosis and 26 years at follow-up. The median follow-up was 21 years (maximum 34 years) from the initial diagnosis.

Late recurrence developed in 806 patients, primarily between 5 and 10 years after diagnosis (69%). Cumulative incidences of recurrent disease at 10, 15, and 20 years were 4.4%, 5.6%, and 6.2%, respectively.

Survivors of astrocytoma had the highest cumulative 20-year risk at 14.4%, followed closely by survivors of Ewing sarcoma (13.0%). Recurrence rates were lowest for soft tissue sarcoma (5.9%), osteosarcoma (3.8%), neuroblastoma (2.6%), non-Hodgkin’s lymphoma (2.4%), and kidney cancer (0.9%). Recurrence risks for leukemia, other CNS tumors, Hodgkin lymphoma, and other bone tumors ranged from 6.4% to 9.4%.

On multivariate analysis, the greatest independent risk factors for late recurrence were a diagnosis of Ewing sarcoma or a CNS tumor, combination treatment with chemotherapy and radiation, earlier treatment era, and fewer years since diagnosis (p < 0.001 for all).

After 217,127 person-years of follow-up, 93% of childhood cancer survivors with no recurrence were alive, compared with 49% of those who had a late recurrence.

“For most pediatric cancers, relapse after 15 years of recurrence-free survival is rare,” the authors note.

“Future research is needed to determine the risk of recurrence in subgroups of survivors and the cost-effectiveness of long-term disease surveillance in at-risk patient groups,” the researchers conclude.

They add, “By understanding the diagnosis-specific risks, patients, families, and their medical providers can be better informed of the probability of cure.”

Reference:
J Natl Cancer Inst 2009;101:1709-1720.