Utility of interim blood tests for cancer screening in Li-Fraumeni syndrome.

Comprehensive annual screening reduces cancer-related mortality in Li-Fraumeni syndrome (LFS), a cancer-prone disorder caused by pathogenic germline TP53 variants. Blood tests at months 4 and 8 between annual screening are recommended but their effectiveness in early cancer detection has not been established. Interim blood counts and inflammatory biomarkers were evaluated in 132 individuals with LFS (112 adults, 87 female, median age 36 years [range 3-68], median follow-up 37 months [range 2-70]) and test abnormalities were observed in 225 (35%). Thirteen cancers in 12 individuals were diagnosed between annual screenings but only one cancer (colorectal adenocarcinoma) was diagnosed due to an abnormal interim blood test. Fisher's exact test and generalized estimating equation models found no statistical associations between cancer diagnoses and any test abnormality. Four- and 8-monthly interim screening blood tests may not be of independent benefit for cancer detection in LFS, but annual cancer screening and personalized follow-up remain essential.