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Objective Breast, lung, colon cancers are the ‘big killers’ in oncology. Access to innovative treatments lags behind in low-income and middle-income countries. We investigated the geographic distribution of industry-sponsored trials; and whether results were reported in clinical trial registries.Methods and analysis We conducted a search in ClinicalTrials.gov by: (i) study type: interventional; (ii) condition: breast, lung, colon cancer; (iii) phases: I–IV; (iv) funder: industry. Trials registered as of 30 June 2018 were extracted; for completed trials, a second extraction was performed on 30 September 2022.Results We included 4177 trials. Phase I–IV trials involving only high-income countries were 3254/4177 (77.9%), while 923/4177 (22.1%) trials included at least one site in middle-income countries (MICs). Most phase III trials (416/688; 60.5%) involved MICs, including only lower MICs (6/416, 1.4%), only upper MICs (225/416, 54.1%) and lower and upper MICs (185/416, 44.5%). Phase IV trials involved MICs in 45/89 (50.6%) cases. Phase I and II trials included MICs in smaller proportions (72/950, 7.6% and 390/2450, 15.9%, respectively). No trials were run in low-income countries (LICs). Among completed trials, 430 out of 1854 (23.2%) involved MICs. Results had not been entered in the registry in 63.4% (1176/1854) of trials overall and 49.5% (213/430) of trials involving MICs.Conclusion Trials for breast, lung and colon cancers are increasingly delocalised to countries likely unable to get access to innovative medicines. Furthermore, LICs are not hosting any industry-sponsored trials. Measures are needed to ensure benefit-sharing for trials countries; to improve transparency and to stimulate research addressing the needs of LICs.