Methods regarding local regional treatment in situ for an individual, such as of a tumor, are provided herein. A hydrogel composition is generated in situ in the tumor by administering a polymer, such as a polysaccharide or a polyamino acid, with a therapeutic agent, such as a radionuclide or a drug, and administering a cross-linking agent. The hydrogel/therapeutic agent composition is retained in the tumor for safe and efficient tumor therapy. Alternatively, a hydrogel composition is generated in situ in an artery which nourishes a tumor to occlude the artery.