Beneath the Aggregate: Subtype-Level Equity Gaps in Global Cancer Clinical Trials

Global equity research in oncology clinical trials has typically treated cancer as a single category, which obscures a real possibility: that representation gaps vary by cancer subtype rather than applying uniformly across the disease as a whole. This paper re-examines an original 200-trial sample of oncology clinical trials, first assembled for a broader monograph comparing Alzheimer's disease and cancer, at the level of individual cancer subtypes, and supplements it with a dedicated 882-trial India-sited dataset to trace subtype-specific patterns in sponsorship and research independence. Among the 113 trials, just over half the sample, with a clearly identified cancer subtype, real variation emerged beneath the aggregate picture reported previously. Gastric cancer trials carried markedly higher eligibility barriers than the sample average: a 66.7% biomarker or imaging requirement and full comorbidity exclusion, against roughly 15% and 60% respectively across the whole cancer sample, a pattern that lines up with the same endoscopy and imaging scarcity already documented across low- and middle-income health systems generally. Breast cancer trials showed the strongest low- and middle-income country site representation of any subtype examined, at 13.3% against a near-zero baseline elsewhere. The India dataset drew a sharper line still: cervical and liver cancer, two subtypes carrying disproportionate global disease burden in low- and middle-income countries, showed a predominantly domestic-research pattern, 67.4% and 68.2% India-only, respectively, with correspondingly low industry sponsorship, while breast, lung, and hematologic malignancy trials followed the extractive, multinational pattern already documented at the whole-disease level. Hematologic malignancy trials showed no low- or middle-income country site representation at all, alongside the highest comorbidity exclusion of any subtype, consistent with published eligibility criteria for cell-based and transplant-adjacent trials that routinely exclude patients for infectious markers, HIV, hepatitis B and C, that are themselves more prevalent in the same populations these trials fail to reach. Taken together, these findings suggest a cancer subtype's equity profile tracks its own disease-burden geography more closely than any disease-wide average can show, with direct consequences for where subtype-specific trial reform and research investment would do the most good.