For families carrying a germline TP53 mutation, childhood is not a reprieve from cancer risk — it is the period when surveillance arguably matters most. Li-Fraumeni Syndrome compresses the cancer clock dramatically, making early, structured monitoring in pediatric carriers a genuine life-or-death clinical question. Yet until now, real-world adherence and the downstream burden of false alarms in this population had not been rigorously quantified.
The SWEP53 study tracked 37 children under 18 across Sweden from 2016 to 2024, all either confirmed TP53 pathogenic variant carriers or carrying a 50% probability based on family history. The surveillance protocol was intensive: quarterly clinical exams, abdominal ultrasound, and urine steroid profiling every three months. Adherence was notably high, ranging from 77% to 97% across components, with urine steroid sampling the weakest link, attributed to logistical fatigue and motivation. Two cancers were identified during the study period; one was caught through the surveillance program itself. Germline testing clustered heavily within the first year of enrollment, a statistically significant pattern suggesting families move quickly toward genetic clarification once enrolled. The false-positive rate reached 12% per person-year, with clinical examination driving 60% of those signals and ultrasound contributing another 27%. Over a third of participants experienced at least one false positive, with a median time to first false alarm of just 1.3 years — prompting imaging or specialist referral in most cases and invasive diagnostics in one.
This is incremental but operationally important evidence. The cohort is small, as expected for a rare syndrome, limiting statistical power and generalizability. However, the prospective nationwide design gives it credibility within its constraints. The 12% annual false-positive rate is clinically meaningful: it quantifies a burden that surveillance guidelines have historically underweighted. For health systems and families weighing intensive monitoring protocols, understanding that more than one-third of pediatric carriers will face at least one unnecessary diagnostic cascade within roughly 15 months reframes the risk-benefit calculus — particularly relevant as germline cancer predisposition testing becomes increasingly accessible.