This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Matthews, W. Articles by Pass, H. I. Search for Related Content PubMed PubMed Citation Articles by Matthews, W. Articles by Pass, H. I.

In Vitro Photodynamic Therapy of Human Lung Cancer: Investigation of Dose-Rate Effects

Thoracic Oncology Section [W. M., R. R. P., S. E., H. I. P.] and Experimental Phototherapy Section [J. C., J. B. M.], National Cancer Institute, NIH, Bethesda, Maryland 20892

The influence of light dose-rate delivery was studied in human lung adenocarcinoma A549 cells treated with hematoporphyrin derivative (Photofrin II)-based photodynamic therapy. Clonogenic cell survival curves were generated for cells treated for 2 h with 25 µg/ml of Photofrin II followed by exposure to light delivered at 0.3, 0.15, 0.075, or 0.0375 milliwatts/cm². Cellular sensitizer levels, as determined by fluorescence measurements, remained constant over the entire time course of all light exposures. As the dose rate of light delivery was decreased, a significant increase in cell survival was observed at equal light energies (225 mJ/cm²). The enhancement in survival from the highest to the lowest dose rate used was 1.6-fold (at the 50% survival level). These findings may have important clinical implications relating to photodynamic therapy of tumors and may provide a partial explanation for treatment failure.

¹ To whom requests for reprints should be addressed, at Head, Thoracic Oncology Section, Senior Investigator, Surgery Branch, National Cancer Institute/NIH, Building 10, Room 2B07, Bethesda, MD 20892.

Received 8/25/88. Revised 12/20/88. Accepted 1/ 3/89.