Prognostic significance of the relapsefree interval after radiotherapy in Hodgkin's disease

Data on the temporal distribution of initial relapses after radiotherapy in 296 cases of Hodgkin's disease have been analyzed. Relapses were not randomly distributed; instead, they exhibited a pronounced clustering during the first 2 years, and the cumulative relapse curve reached a plateau by 3 to 5 years, indicating that the probability of developing an initial relapse later than 5 years after treatment must be quite small, almost certainly less than 5%. It follows that relapse-free five-year survivors have at least a 95% chance of being permanently cured. Relapse rates and relapse-free interval depend significantly on clinical stage and on the presence or absence of constitutional symptoms. After-survival of groups of 1- and 2-year survivors was strikingly better in those who were relapse-free during the interval than in those with one or more interval relapses. It is concluded that the cumulative relapse rate at 3 years represents a useful and valid early prognostic index.