The present invention concerns a therapeutically labeled napthodianthrone or phenanthro[1,10,9,8-opqra]perylene-7,14-dione compound, which comprises a chemical element or an isotope that has an unstable nucleus and emits radiation during its decay to a stable form sufficient to destroy neighboring cells or tissues for use in a targeted radiotherapy to enhance curability of a warm-blooded animal that has been subjected to a necrosis-inducing antitumor therapy. A particular advantage of present invention is that viable rim resistant to a necrosis-inducing antitumor therapy such as vascular targeting agent (VTA) can be supplemented by one single or repeated doses of a therapeutically radiolabeled small molecule necrosis-avid chemical compound treatment to enhance the curability. Examples of necrosis inducing therapies are for instance minimally invasive tumor ablations applied chemically by percutaneous injection of ethanol or acetic acid, or physically by cryotherapy, microwave, focused ultrasound, interstitial laser therapy and radio-frequency ablation (RFA); by chemotherapies using cytotoxic agents or vascular targeting agents (VTA); and by external or internal radiotherapies.