Radiation therapy combined with photofrin or 5-ALA: effect on Lewis sarcoma tumor lines implanted in mice. Preliminary results.
OBJECTIVE
Ionizing irradiation is a well-established therapeutic modality for cancer. Photodynamic therapy (PDT), especially with 5-ALA and Photofrin, is highly effective in some tumor types. Chemical modifiers, so-called radiosensitizers, are used in order to increase the efficacy of radiotherapy. Most of the known and routinely used radiosensitizers are not tumor selective, so that the normal tissue reaction toxicity is also increased. In the present study we investigated whether a porphyrin derivative that is currently used as a tumor-photosensitizing agent in photodynamic therapy (PDT) may also act as a tumor-specific radiosensitizer.


METHODS
For our investigation we used Balb/c mice implanted with Lewis sarcoma and irradiated with 3 Gy combined with injection of 5-ALA or Photofrin at various concentrations before irradiation.


RESULTS
5-ALA had no effect as a radiosensitizer at any of the concentrations examined. Photofrin at a concentration of 5 mg/kg proved to be a chemical modifier of ionizing radiation, delaying tumor growth and reducing the overall tumor volume by about 50% after six days.


CONCLUSIONS
Photofrin has marked efficacy as a radiosensitizer and can be used in the future as a selective tumor radiosensitizer.
Schaffer
Moshe
M
Department of Radiation Therapy, University of Munich, Germany. m.shaffe@helios.med.uni-muenchen.de
Schaffer
Pamela M
PM
Jori
Giulio
G
Corti
Luigi
L
Sotti
Guido
G
Hofstetter
Alfons
A
Dühmke
Eckhart
E
D000622:Aminolevulinic Acid / Q000627:therapeutic use*; D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017323:Dihematoporphyrin Ether / Q000627:therapeutic use*; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D012513:Sarcoma, Experimental / Q000188:drug therapy* / Q000532:radiotherapy*
D000970:Antineoplastic Agents; D017319:Photosensitizing Agents; D011838:Radiation-Sensitizing Agents; D000622:Aminolevulinic Acid; D017323:Dihematoporphyrin Ether