Geographic equity in oncology clinical trials in Spain: fragmentation, indicators, and evidence

Spain is one of Europe’s leading countries in oncology clinical research by trial volume, with sustained growth in trial activity. However, the geography of innovation is not necessarily the geography of need. Using publicly reproducible indicators, we describe pronounced territorial concentration in oncology clinical research activity across Spain’s autonomous communities (CCAA) and discuss the implications for equity of access to therapeutic innovation. Two complementary measures were juxtaposed: (i) REec-derived onco-hematology medication trial presence by CCAA in 2022 (reflecting where trials are activated), and (ii) population-normalized oncology trial participations per 100,000 inhabitants in 2016-2020 derived from AECC reporting (reflecting realized access to enrollment over time). Both indicators converge on a consistent pattern: trial activity and participation are concentrated in a small number of CCAA. Madrid and Catalonia together account for 41.4% of trial presences in 2022 (640 of 1546), and population-normalized participation ranged from 0.2 to 41.9 per 100,000 inhabitants across regions. When viewed alongside regional incidence and mortality patterns and contemporary mortality trends, research intensity does not appear to align consistently with cancer burden, suggesting that historical infrastructure, administrative capacity, and trial hub effects may be stronger determinants than epidemiological need. These findings support a shift from ad hoc assessments to routine monitoring of research equity, leveraging REec and existing national cancer-indicator platforms, alongside targeted capacity-building and networked collaboration to ensure that access to clinical research is not determined by place of residence.