Photodynamic therapy for esophageal lesions: selectivity depends on wavelength, power, and light dose.
BACKGROUND
Photodynamic therapy with 5-aminolevulinic acid-induced photosensitization could selectively eliminate esophageal epithelial lesions. This study aimed at optimizing laser parameters for 5-aminolevulinic acid photodynamic therapy of the normal rat esophagus.


METHODS
Sixty rats received 200 mg/kg 5-aminolevulinic acid orally and were illuminated 3 hours later with either 633 or 532 nm light (n = 30 for each group) through an endoesophageal balloon catheter. Rats received either 8.3 or 25 J/cm diffuser, applied with a 33, 100, or 300 mW/cm diffuser. During illumination, tissue fluorescence measurements and light dosimetry were done. Rats were sacrificed at 48 hours after photodynamic therapy.


RESULTS
During illumination, protoporphyrin IX fluorescence declined faster when a higher power output was used. Fluence rate at the esophageal surface was highest for 633-nm light. At 532 nm, light caused less damage to the epithelium and muscle than 633-nm light. Illumination with 33 mW resulted in selective epithelial ablation, whereas illumination with 300 mW caused muscle damage with minor epithelial damage.


CONCLUSIONS
The assumed selective epithelial damage of 5-aminolevulinic acid photodynamic therapy in the esophagus largely depends on the combination of wavelength, power, and light dose applied. Most selective epithelial damage was found when low-power 633-nm light was used.
van den Boogert
J
J
Laboratory for Experimental Surgery, Erasmus University, Rotterdam, The Netherlands.
van Staveren
H J
HJ
de Bruin
R W
RW
Eikelaar
J H
JH
Siersema
P D
PD
van Hillegersberg
R
R
D000622:Aminolevulinic Acid; D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000473:pathology; D004938:Esophageal Neoplasms / Q000188:drug therapy* / Q000473:pathology; D004947:Esophagus / Q000187:drug effects / Q000473:pathology; D006414:Hematoporphyrin Photoradiation; D011230:Precancerous Conditions / Q000188:drug therapy* / Q000473:pathology; D051381:Rats; D016896:Treatment Outcome
D000622:Aminolevulinic Acid