CDKN2A and neoplasm: In these two patients, there was noticeably higher P16INK4a methylation at relapse; this was not the case in the individuals without tumor recurrence.565 Jin et al. found that cfDNA follow-up could detect colon cancer recurrence early, with circulating tumor DNA reappearing in 70% of patients (14 cases) before recurrence, approximately eight months earlier than imaging suggested.566 Therefore, early tumor relapse detection is made possible by dynamic monitoring of circulating tumor DNA methylation, which aids in clinical decision-making.