OBJECTIVES: One of the major concerns is the burden COVID-19 will impose on the health care system worldwide. Brazil is the second country with the most confirmed cases (more than 1 million cases and 60 thousand deaths). The study aims to evaluate the impact on oncologic treatments by COVID-19 pandemic. METHODS: Design: retrospective non-interventional study using population-based health administrative databases. Setting: payer provider healthcare organization. Participants: 41,640 individuals attended by plan. Outcomes: number of chemotherapy and radiotherapy prior authorizations during two periods of 90 days, before (P1) and after (P2) the first registered case of COVID-19. Statistics: data were analyzed descriptively considering measures of central tendency for continuous variables and frequency measures for categorical variables. Microsoft Excel® v2010 and Qlik Sense® v13.21 were used to data and statistics. RESULTS: During the study period (180 days), 1,171 patients underwent chemotherapy (P1=630 and P2=541) a reduction of 14.1%. Regarding radiotherapy, decrease was 28.1% (55, P1=32 and P2=23). The most frequently neoplasm were prostate (27.1%), breast (20.4%), bronchi and lungs (5.1%), colon (2.7%), other types (44.7%). Reduction in tests performed was 35.0% (P1= 1,542; P2= 1,002) and hospitalizations was 49.4% (P1= 310; P2= 157). CONCLUSIONS: Local health guidelines recommended when possible to postpone procedures due risk of COVID-19 infection during hospital stay and block of hospital beds to attend to the pandemic. There was a decrease in Cancer treatments, with a greater reduction in radiotherapy. Even after the critical period, we didn´t observe a gradual return of cancer treatments to the standard, as observed in tests and other types of treatments performance, including hospitalizations of other causes. If trend continues, there is a possibility of cancer cases worse and negative impact of new neoplasm diagnosis.