Incidence and survival of uveal melanoma in Northern Ireland: how incomplete data can skew results in rare cancers.

This study illustrates the impact of incomplete population-wide data, serving as a real-world lesson in case-identification bias. Rare cancers are at higher risk of omission due to systemic failures as the small numbers involved are not detected by system-wide validation procedures. Following this study, data-transfer agreements between England and NI were actioned, preventing future data-omissions. We present survival and incidence data for UM in NI for the first time, showing the incidence is amongst the highest in Europe, with good survival rates.