No abstract

Photodynamic therapy, employing either hematoporphyrin derivative or dihematoporphyrin ether as the photosensitizer and an argon-pumped tunable dye laser as the activating light source, was used to treat ten patients who had primary or recurrent basal or squamous cell carcinoma or infiltrating ductal cell carcinoma lesions metastatic to the skin. Of the 155 sites that were treated, various degrees of edema, erythema, and necrosis, sometimes accompanied by blistering, were evident in all areas within 24 to 48 hours of light treatment. While our follow-up periods are short, four patients are free of disease at eight months or more posttreatment, two patients have had recurrent and/or persistent disease within four months, and four patients died within nine months from metastatic disease or unrelated disorders. Continued investigation into the use of photodynamic therapy for treatment of malignant lesions appears warranted, based on these preliminary clinical results.

Recent experimental studies of airborne contaminants found in the carbon dioxide laser plume have raised questions as to the potential danger of serious viral transmission during laser procedures. These concerns originated from a study of the human papilloma wart virus that reported intact strands of the DNA virus in the laser plume during the ablation of verrucae with the carbon dioxide laser. However, the study did not demonstrate the viability of such viral remnants. Such viability is difficult to demonstrate due to the strict species specificity of the papilloma virus, thus precluding the possibility of transinfection of an animal model with human papilloma DNA. We have therefore conducted a retrospective study to explore both the incidence of acquired lesions among laser users and also the details predisposing to the development of such lesions. Although a small percentage of our respondents reported acquired lesions, the role of the laser plume as the primary source of such lesions is unlikely. It is our opinion that the majority of reported lesions were acquired through direct contact, and proper sterile technique would significantly reduce the transmission of human papilloma virus during therapeutic procedures.

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 (PDT) with Photofrin II was administered over a 7-year period to 17 patients with recurrent carcinoma in situ (CIS) of the vulva, vagina, and perianum. Ten patients were treated two or three times after average intervening periods of 23 and 19 months, respectively. A histologically complete response at 3 months after the PDT session was achieved for 27 of 38 (71%) anatomic sites. Ten patients of this group remain free of recurrences for periods of 2-7 years. Condylomata acuminata associated with CIS in 16 of 17 patients recurred rapidly in 7 patients after PDT. Only short-term palliative results were achieved for 4 patients treated with PDT for invasive carcinoma. Fifteen patients experienced a significant skin reaction to direct sunlight during a 7-week period post-PDT.