title: [Concomitant chemo-radiation treatment of malignant tumors: biological bases].
abstract: Concomitant radio-chemotherapy is widely used in the treatment of various localisations of cancer. Numerous interactions are known between ionizing radiation and cytotoxic agents, which in vitro may modify the dose-response relationships. The main interactions are spatial cooperation, independent cell kill, cell synchronization, inhibition of repair of radiation damage, reoxygenation, reduction of the hypoxic fraction and increased apoptosis. Exposure of irradiated cells to cytotoxic agent lead to increase the number of unrepaired double-strand breaks. By this mechanism the action of DNA repair of both therapeutic modalities enhance therapeutic efficiency. The main effects of chemoradiotherapeutic combination in the laboratory are inhibition or antagonism, sub-additive, additive and supra-additive effects. The most important for clinical practice are supra-additive effects, when the cytotoxic effect of the combination is greater than the sum of the effects of radiotherapy alone and that of chemotherapy alone. It is however difficult to extrapolate laboratory and experimental results to clinical practice because the conditions for interaction of chemo- and radiotherapy in vitro are different. Clinical conditions usually are more compatible for additive and sub-additive interactions. The main role of laboratory and experimental investigations is to propose new drug--radiotherapy combination to phase II trials.
authors.affiliation: Kauno medicinos universiteto Onkologijos klinika, Eiveniu 2, 3007 Kaunas. onko@takas.lt
authors.forename: Arturas
authors.initials: A
authors.lastname: Inciūra
authors.forename: Elona
authors.initials: E
authors.lastname: Juozaityte
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D003131:Combined Modality Therapy; D004260:DNA Repair / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D006801:Humans; D008297:Male; D009362:Neoplasm Metastasis / Q000188:drug therapy / Q000517:prevention & control / Q000532:radiotherapy; D009369:Neoplasms / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D011837:Radiation-Protective Agents / Q000627:therapeutic use; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use; D011853:Radiobiology; D011879:Radiotherapy Dosage; D016032:Randomized Controlled Trials as Topic; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects
chemical_list: D000970:Antineoplastic Agents; D011837:Radiation-Protective Agents; D011838:Radiation-Sensitizing Agents