PHOTODYNAMIC THERAPY OF HEAD and NECK SQUAMOUS CELL CARCINOMA: OPTICAL DOSIMETRY and CLINICAL TRIAL

Abstract

This paper reports the retrospective comparison of a PDT dosimetry model with the current results of an ongoing clinical trial on photodynamic therapy (PDT) for head and neck squamous cell carcinoma (HNSCC). The model is based on the assumption that tumor eradication requires a minimum absorption of radiant energy by the tumor‐localized porphyrins. The diffusion approximation was employed to calculate the incident light dose required to attain the minimum absorbed energy density at tumor boundaries most distant from the light source. Dosimetry tables for HNSCC were calculated with estimated tissue parameters, giving the PDT light dose for front surface exposure (FS) and illumination by interstitial cylindrical diffuser fibers (CI) in terms of the tumor dimensions. The model includes a correction for the photobleaching of the localized photosensitizer by the therapeutic light. The PDT trial was carried out on nine patients with previously untreated or recurrent early stage tumors and one patient with a recurrent advanced stage tumor. A complete response was obtained in 83% (10/12) of the sites treated. The calculated doses for FS and CI exposures vary from comparable with to three‐fold lower than the actual doses for each complete response tumor site.

Photodynamic therapy

“…There are several clinical studies with more than 270 patients quoted in the literature [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. All together, a complete response rate of about 87.8% (245/270) is reported.…”

Advances in photodynamic therapy for the treatment of head and neck cancers

“…Grossweiner treated nine patients with early recurrent carcinomas of the oral cavity with light administration 24 hours after intravenous Photofrin injection. Eight of nine (88%) patients had a complete response after one PDT treatment [6].…”

Photodynamic therapy

“…Literature results are reported for 164 patients with primary, recurrent, and metastatic head and neck cancers from 1984-1990 with an overall CR rate of 28% [6]. In our study, 26 patients were treated for squamous cell carcinoma (SCC) of the head and neck from 1985-1989 [9,10]. All patients were administered PF at 2.0 mg kg -1 and treated with 630 nm light from a tunable dye laser at 24 h post-injection.…”