Survival differences between patients with Hodgkin lymphoma treated inside and outside clinical trials. A study based on the EORTC-Netherlands Cancer Registry linked data with 20 years of follow-up.

The survival of patients diagnosed with Hodgkin lymphoma (HL) has improved from 70% to 90% in clinical trials. However, population-based data has shown lower survival. In this study, clinical trial data were linked with cancer registry to identify trial and non-trial participants and differences in overall survival and associated factors were assessed. In 1986-2004, 27% of HL patients aged 15-70 years participated in clinical trials. Compared to non-trial participants, trial participants were younger (median age, 31 vs. 34 years), had staging registered more accurately and had an 8% higher 20-year survival rate (73% vs. 65%). After adjusting for baseline differences, no differences in survival (hazard ratio = 0·96, 95% confidence interval 0·82-1·12), or in subgroup analysis according to stage, remained. Over time, increased administration of chemotherapy in combination with radiotherapy, together with the decreased use of radiotherapy alone was observed among the trial population. This trend was later followed in non-trial participants, coinciding with a similar 'take-up' in survival. The observed superior survival among patients with HL treated in clinical trials can be largely explained by the differences in baseline characteristics, particularly younger age. High trial participation rate and centralized expertise facilitates the implementation of trial findings to real-world practice.