Johannesburg Cancer Study (JCS): contribution to knowledge and opportunities arising from 20 years of data collection in an African setting.

•Cancer cohort recruitment methodology for low resource environment.•20 years of data to identify risk factors for cancer development in black patients.•24 971 black patients with histologically proven cancer of any type were enrolled.•Serum and DNA samples are available for serological and genomic analysis.•Viral infections & leading lifestyle risk factors are key in cancer aetiology in SA.