Interval-by-interval Cox model analysis of 3680 cases of intraocular melanoma shows a decline in the prognostic value of size and cell type over time after tumor excision.

In a selected group of 3680 patients treated by ocular excision for uveal melanoma, 1178 deaths were attributed to this tumor during 20 years following ocular excision. Survival time was divided into intervals containing an equal number of deaths, and coefficients of the Cox statistical model were independently derived for each interval. This analysis revealed a statistically significant decline over time in the prognostic value of largest tumor dimension (LTD) and Callender cell type (CT). Mathematical considerations suggest that the prognostic value of parameters derived from other cancers may also decline with time following excision of the primary tumor.