In vivo light transmission spectra in EMT6/Ed murine tumors and Dunning R3327 rat prostate tumors during photodynamic therapy.
OBJECTIVE
Variations in the optical coefficients in tissue and the photosensitizer during photodynamic therapy (PDT) will require adjustment of the light dose during the course of therapy. We have studied the dynamics using light transmission spectra for two different tumor models when tetrasulfonated aluminum phthalocyanine (AlPcS4) was used as photosensitizer.


METHODS
Spectra were measured noninvasively in the EMT6/Ed murine tumor model, and with interstitially implanted source and probe fibers in the Dunning R3327-AT rat tumor model. Measurements were performed in the range 600-840 nm, using a tunable dye laser, a diode laser, and a Ti:Sapphire laser. AlPcS4 has absorption in the range 600-700 nm with an absorption peak at 670 nm in saline.


RESULTS
The in vivo spectrum of AlPcS4 both in the EMT6/Ed tumor model and the Dunning R3327-AT tumor model differs from the spectrum of AlPcS4 in saline. The absorption at 670 nm was reduced, whereas the absorption at 640 nm increased. Exposure of phototherapeutic levels of light caused reduced light absorption by the photosensitizer and further spectral shift.


CONCLUSIONS
We found that the AIPcS4 absorption spectrum changes in a biological environment, and we also observed increased light transmission at the treatment wavelength during PDT in both tumor models. Instability in the absorption spectrum of the photosensitizer may influence the effectiveness of PDT.
Ballangrud
A M
AM
Department of Surgery, Cross Cancer Institute, Edmonton, Alberta, Canada.
Barajas
O
O
Georgousis
A
A
Miller
G G
GG
Moore
R B
RB
McPhee
M S
MS
Tulip
J
J
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D007211:Indoles / Q000627:therapeutic use*; D007834:Lasers; D008297:Male; D051379:Mice; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000188:drug therapy*; D009942:Organometallic Compounds / Q000627:therapeutic use*; D019047:Phantoms, Imaging; D010778:Photochemotherapy; D011471:Prostatic Neoplasms / Q000188:drug therapy; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D051381:Rats; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D007211:Indoles; D009942:Organometallic Compounds; D011838:Radiation-Sensitizing Agents; C048577:aluminum tetrasulfophthalocyanine