The present invention provides a method of treating cancer in a patient including (1) a step of applying to a tumor a composition comprising (a) 0.01 to 3.5 weight percent of hydrogen peroxide in a final formulation and (b) hyaluronic acid or a salt of the hyaluronic acid, in which applying the composition is an intratumoral injection, and (2) a step of performing a radiotherapy treatment or an anti-cancer chemotherapy treatment at the same time as or after the step (1).
