Poor Outcome of Pediatric Patients with Acute Lymphoblastic Leukemia Harboring Low P16 Deletion Ratio: A Post-Hoc Analysis from a Prospective Cohort

Kun-Yin Qiu,1,2,* Xiong-Yu Liao,1,2,* Hai-Lei Chen,2,3,* Hong Zheng,1,2,* Jian-Pei Fang,1,2 Dun-Hua Zhou1,2 1Department of Hematology/Oncology, Children’s Medical Center, Sun Yat-sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People’s Republic of China; 2Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong, People’s Republic of China; 3Morphologic and Biochemical Laboratory of Pediatric Hematology, Children’s Medical Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jian-Pei Fang, Department of Hematology/Oncology, Children’s Medical Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong, People’s Republic of China, Tel/Fax +86 20 81332630, Email fangjpei@mail.sysu.edu.cn Dun-Hua Zhou, Department of Hematology/Oncology, Children’s Medical Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong, People’s Republic of China, Tel/Fax +86 20 81332630, Email zhoudunh@mail.sysu.edu.cnObject: The prognostic significance of P16 (CDKN2A) deletion (P16del) in pediatric acute lymphoblastic leukemia (ALL) remains controversial, potentially due to the historical reliance on binary classification.Methods: In this prospective cohort study (SCCLG-ALL-2016 protocol), we analyzed 413 pediatric ALL patients. P16del status and ratio were quantified using standardized FISH. Statistical models adjusting for key prognostic factors were performed. Piecewise linear regression identified prognostic thresholds for P16del ratio. Survival outcomes (relapse-free survival, RFS; overall survival, OS) and interactions with minimal residual disease (MRD) were assessed.Results: P16del prevalence was 18.2% (75/413). Multivariable analysis confirmed P16del as an independent adverse prognostic factor (RFS: HR=2.2, p=0.020; OS: HR=2.7, p=0.024). Crucially, a nonlinear dose–response relationship identified 0.8 as the critical P16del ratio threshold: Below 0.8, each unit ratio increase conferred a 93% higher relapse/death risk (adjusted LogHR=1.93, p=0.031); above 0.8, higher ratios reduced risk by 33% (adjusted LogHR=0.67, p=0.048). Patients with low ratios (< 0.8, n=37) had significantly inferior 5-year outcomes (RFS: 57.7%, OS: 72.2%) compared to high ratios (≥ 0.8, n=38; RFS: 88.5%, OS: 94.7%) (p< 0.001). The prognostic impact of MRD was critically dependent on P16del ratio: Low ratio with D33 MRD+ predicted catastrophic outcomes (5-year RFS=27.8%), while high ratio patients maintained excellent survival regardless of MRD status (D33 MRD+ RFS=100%). High-ratio patients exhibited enrichment for RAS mutations (p=0.046).Conclusion: The identified P16 deletion ratio threshold of 0.8 may guide precision risk-adapted therapy in pediatric ALL, but its clinical utility must be validated in larger, diverse cohorts before implementation.Keywords: children, acute lymphoblastic leukemia, P16 deletion, prognostic biomarker, minimal residual disease