Short NK- and Naïve T-Cell Telomere Length Is Associated with Thyroid Cancer in Childhood Cancer Survivors: A Report from the Childhood Cancer Survivor Study

BACKGROUND: Survivors of childhood cancer are at risk for therapy-related subsequent malignant neoplasms (SMN), including thyroid SMN. Telomere length (TL) is associated with cancer risk, but the relationship between TL and SMN risk among survivors is less clear. METHODS: We conducted a nested, matched case-control study of radiation-exposed 15-year+ adult survivors of childhood cancer with thyroid SMN (cases) and without SMN (controls). Forty-six cases were matched to 46 controls by primary diagnosis, chemotherapy (yes/no), radiation field, and follow-up duration. Lymphocyte TL (LTL) was measured by telomere flow-FISH cytometry using blood samples banked at a mean of 38.9 years (cases), 39.2 years (controls). Genetic variation in telomere genes was assessed by whole genome sequencing. Point estimates for LTL <10th percentile were determined for cases and controls. Five out of 15 cases with a rare indel or missense variant had naïve T-cell LTL <10th percentile, compared with one out of eight controls. CONCLUSIONS: Long-term survivors have shorter than expected LTL, a finding that is more pronounced among survivors with thyroid SMN. IMPACT: The long-term impact of childhood cancer treatment on immune function is poorly understood. Our findings support immune function studies in larger survivor cohorts to assess long-term deficits in adaptive and innate immunity that may underlie SMN risk.