Abstract: Methods of treating tumors, lesions, and cancers comprising delivering to the affected site a combination of peroxide and hypochlorite anion. Hydrogen peroxide and sodium hypochlorite are possible sources of peroxide and hypochlorite anion, respectively. The reactants may be injected simultaneously or sequentially, and combine at the site to produce singlet oxygen. Singlet oxygen may be delivered to the treatment site or generated at the treatment site. Isotopes are also synergistically used in conjunction with singlet oxygen. The isotopes may be radioactive isotopes, non-radioactive isotopes, or both.