Background: The appearance of the new coronavirus, SARS-CoV-2, in Wuhan - China, in 2019 led to the declaration of a COVID-19 pandemic by the World Health Organization. Peru confirmed its first case on March 6, 2020, prompting a significant change in medical care. Purpose: Our objective was to determine the impact of the COVID-19 pandemic on cancer treatment in Peru. Methods: A retrospective analysis of hospital data from the National Institute of Neoplastic Diseases revealed substantial decreases in oncological treatments in 2020 compared to 2019. Results: Oncological treatments involving bone marrow transplantation had a greater impact between the months of April and September, at -100% (p=0.003). However, treatments involving surgery in April (-95% [p≤0.001]), radiotherapy in May (-76% [p=0.002]) and chemotherapy in June (-71% [p≤0.001]) also showed significant impacts. Comparativ...