Monitoring tumor response during photodynamic therapy using near-infrared photon-migration spectroscopy.
Benzoporphyrin-derivative (BPD)-monoacid-ring A photodynamic therapy (PDT) was performed on subcutaneous tumor implants in a rat ovarian cancer model. In order to assess PDT efficacy the tumor and normal tissue optical properties were measured noninvasively prior to and during PDT using frequency-domain photon migration (FDPM). FDPM data were used to quantify tissue absorption and reduced scattering properties (given by the parameters mu a and mu's, respectively) at four near-infrared (NIR) wavelengths (674, 811, 849 and 956 nm). Tissue physiologic properties, including the in vivo concentration of BPD, deoxy-hemoglobin (Hb), oxy-hemoglobin (HbO2), total hemoglobin (TotHb), water (H2O) and percent tissue hemoglobin oxygen saturation (%StO2), were calculated from optical property data. PDT efficacy was also determined from morphometric analysis of tumor necrosis in histologic specimens. All the measured tumor properties changed significantly during PDT. [Hb] increased by 9%, while [HbO2], [TotHb] and %StO2 decreased by 18, 7 and 12%, respectively. Using histologic data we show that long-term PDT efficacy is highly correlated to mean BPD concentration in tumor and PDT-induced acute changes in [HbO2], [TotHb] and %StO2 (correlation coefficients of 0.829, 0.817 and 0.953, respectively). Overall, our results indicate that NIR FDPM spectroscopy is able to quantify noninvasively and dynamically the PDT-induced physiological effects in vivo that are highly correlated with therapeutic efficacy.
Pham
T H
TH
Laser Microbeam and Medical Program (LAMMP), Beckman Laser Institute and Medical Clinic, University of California, 1002 Health Sciences Road East, Irvine, CA 92612, USA.
Hornung
R
R
Berns
M W
MW
Tadir
Y
Y
Tromberg
B J
BJ
D000818:Animals; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000175:diagnosis / Q000188:drug therapy* / Q000378:metabolism; D018462:Photobiology; D010778:Photochemotherapy; D017785:Photons; D051381:Rats; D011916:Rats, Inbred F344; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
D006454:Hemoglobins