Background: Recent findings that Black and Hispanic patients were significantly underrepresented in industry-sponsored prostate cancer trials warrant a detailed investigation across cancer types to assess the association between funding source and enrollment disparities. Methods: Phase II/III clinical trials in prostate, breast, colorectal, and lung cancers reporting age, gender, race/ethnicity, and reporting NIH or industry as the funding source were considered eligible for inclusion. For age, and gender analysis, all trials were considered eligible. For race/ethnicity analysis, trials recruiting from the United States (US) were considered eligible. Enrollment-incidence ratios (EIR) comparing trial proportion from age/gender or racial/ethnic subgroups against global cancer incidence in the corresponding group (from Global Burden of Disease) or US-population-based incidence in the corresponding racial/ethnic subgroup (from SEER 22), were computed. Trial-level EIRs were pooled using a random-effects model and subsequently stratified by funding source. A univariate meta-regression was conducted to assess the temporal changes in EIR by each funding category. Results: Of 42,390 studies initially identified, 2234 trials (1989-2021) met the eligibility criteria. Regarding age, 361 (16%) trials reported age categories by 65 years threshold. Of 698 trials recruiting from the US, 498 (71%) reported race, and 198 (28%) reported ethnicity. Regarding representation, older adults were under-represented (EIR: 0.66; 95% CI: 0.62-0.70) in the industry but not in NIH-sponsored clinical trials (0.79; 0.62-1.00). Regarding gender, no significant disparity was observed regarding the enrollment of men and women in colorectal and lung cancer clinical trials. In terms of race, there was a greater under-representation of Black patients in industry sponsored trials (0.29; 0.26-0.32) as compared to NIH-sponsored clinical trials (0.65; 0.57-0.74) [P_int<0.01]. Asian patients were significantly overrepresented in industry sponsored trials (3.17; 2.69-3.74) but not in NIH sponsored clinical trials (1.43; 0.85-2.41) [P_int<0.01]. Hispanic patients were significantly under-represented in both, industry (0.27; 0.22-0.34) and NIH-sponsored clinical trials (0.35; 0.22-0.55) [P_int 0.32]. Secondary analyses including trials recruiting exclusively from the US, and analyses by specific cancer types showed consistent results. Recruitment of older adults, men, and Black patients is decreasing over time. Conclusions: There is a consistent under-representation of older adults in industry-sponsored, and of Black and Hispanic patients in both industry-sponsored and NIH-sponsored clinical trials. The under-representation of Black patients is likely to be greater in industry-sponsored trials, which has worsened over the last three decades.