Thomas J. Dougherty

Photodynamic therapy for residual neoplasms of the perianal skin.

PURPOSE: The aim of this study was to evaluate the efficacy of photodynamic therapy in the management of residual neoplasms of the perianal skin. METHODS: This is a retro-spective review. Five patients with pathologic confirmation of residual perianal neoplasms were treated with photodynamic therapy. There were three females. The mean age was 52 (range, 33–79) years. Pathology consisted of Bowens disease in two patients, squamous-cell carcinoma in two patients, and extramammary Pagets disease in one patient. Four patients received one photodynamic therapy treatment and one patient received two treatments three months apart. RESULTS: Treatment was followed by immediate perianal erythema, subsequent blister formation in 36 to 48 hours, and sloughing of the treated area in 72 hours. With a mean follow-up of 5.2 (range, 1–8) years, there were two recurrences. One recurrence was in a patient four years after treatment for Pagets disease, and the other was in a patient nine months after treatment for Bowens disease. The latter was managed successfully with wide local excision. Treatment-related toxicities included significant perianal pain in four patients, controlled with analgesia management. CONCLUSIONS: Photodynamic therapy can successfully be used after wide local excision for residual neoplasms of the perianal skin. Treatment can be rendered with acceptable morbidity.

Potential new photosensitizers for photodynamic therapy

In continuation of the effort to search for an ideal photosensitizer, two groups of potential new photosensitizers were synthesized and investigated for their photodynamic actions against tumors in mice. These were derivatives of methyl pheophorbide-a and of silicon naphthalocyanine. Of the former group, the 2 (1-0--hexyl) ethyl-desvinyl--methyl pheophorbide-a, or }IEDP, was the most active sensitizer. HEDP could be readily produced in large quantities and showed an optimum photodynamic action at 665 mu where it absorbs strongly. Also HEDP was cleared from the mouse skin within 4 days after administration, thus possibly alleviating the long-term phototoxic side-effects observed in Photofrin-based therapy. Of the second group of photosensitizers, the bis (dimethyl hydroxypropylsiloxy) silicon naphthalocyanine (HPSiNc) , and the corresponding acetoxy derivative (APSiNc) were of particular interest. At a drug-light dose of 1.0 mg/kg-135 J/cm2 (delivered by a laser at 772 nm), they showed antitumor activities comparable to that of PhotofrinTM. Further studies on these photosensitizers are warranted.