Objective: to explore the causes and clinical impact of loss to follow-up (LTFU) in patients with differentiated thyroid cancer (DTC) in the nuclear medicine department, Cairo University hospitals.

Methods: In this cross-sectional study, demographic and socio-economic characteristics of DTC patients who failed to show-up for their follow-up appointments as well as the causes of LTFU were assessed through survey questions. Clinical data were obtained from the patient's medical records. The clinical impact was assessed by comparing each patient's serum thyroglobulin (Tg) level, anti-thyroglobulin (anti-Tg) level, neck ultrasound (US) findings and thyroid stimulating hormone (TSH) level before and after LTFU.

Results:91 patients were identified during a period of six months. Regarding the demographic data; the mean age was 47.8 years, 84.6% were females and 38.5% had associated co-morbidities. Regarding the duration of LTFU; 29.6% of patients lost follow-up for less than one year and 49% lost follow-up for one to two years, while 21.4% failed to show-up for more than two years. As regards the cause of LTFU; the predominant cause was financial (36.3%). Financial cause and the presence of other co-morbidities were significantly higher among patients who missed follow-up after the third year (p value = 0.037 and 0.016 respectively). Regarding the clinical impact of LTFU; 20.9% presented with inadequate TSH suppression or hypothyroidism. 18.7% presented with disease progression or recurrence. Disease progression or recurrence were significantly higher among those who did not achieve excellent response prior to LTFU and in high risk patients (p value = 0.012).

Conclusion: Early identification and management of demographic and socioeconomic risk factors for LTFU in DTC patients are important for the prevention of adverse outcomes.