Masoud Panjehpour

Balloon photodynamic therapy of esophageal cancer: Effect of increasing balloon size

Photodynamic therapy is currently being used to treat various malignancies including esophageal cancer. The effect of photodynamic therapy depends upon the concentration of photosensitizing drug, light energy delivered to tissue, and the presence of oxygen in the targeted tissue. We have found that an esophageal centering balloon improves light delivery to esophageal mucosa. However, balloon pressure on esophageal mucosa could possibly reduce mucosal blood flow and oxygenation, therefore reducing the effect of photodynamic therapy. This study was conducted to investigate the effect of balloon pressure on the esophageal wall during photodynamic therapy in the canine esophageal model.

A centering balloon for photodynamic therapy of esophageal cancer tested in a canine model.

Delivery of uniform circumferential light is desirable during photodynamic therapy of early or advanced esophageal cancer in human beings. Studies were performed in the canine esophagus to investigate whether use of a centering balloon would improve circumferential illumination of esophageal mucosa for photodynamic therapy of esophageal cancer. When the centering balloon was used, photodynamic therapy produced uniform and circumferential injury. With the cylindrical diffuser used in human studies, non-uniform and focal esophageal injury occurred. Placement of isotropic probes on the balloon wall allowed measurement and verification of relatively uniform light doses delivered to esophageal mucosa during balloon photodynamic therapy. The centering balloon has a potential role in improving light dosimetry during esophageal photodynamic therapy.

Hyperthermia treatment using a computer-controlled Nd:YAG laser system in combination with surface cooling

An Nd:YAG laser hyperthermia system was used to induce hyperthermia in chemically-induced rat mammary adenocarcinomas. Excessive heating of the surface tissue limits the depth of heating during laser-induced hyperthermia. To determine whether surface cooling would allow heating of deeper tissues, treatment surfaces were cooled using two different techniques. (1) an IV drip in conjunction with oxygen flow directed toward the surface, and (2) moisture saturated oxygen flow from a nebulizer. The laser was interfaced to a computer and a thermometer that provided feedback to maintain the tumor temperature between 43.2- 43.5 degree(s)C. The thermocouple was placed in the base of the tumor and its temperature was used via the feedback system to control laser exposure. All tumors were 1.0 to 2.0 cm in diameter. While both cooling techniques lowered the surface temperature effectively, nebulizer technique was preferred due to better control of surface cooling and less fluid accumulation around the treatment area. Nd:YAG laser hyperthermia delivered in conjunction with surface cooling using the nebulizer technique produced efficient heating of rat mammary adenocarcinomas to an approximate depth of 15 mm without overheating the surface tissue.

Laser-induced fluorescence quantitation of choloroaluminum phthalocyanine tetrasulfonate concentration in rat tissue

The determination of photosensitizer concentration in tissue will allow improved planning of photodynamic therapy. Laser-induced fluorescence (LIF) has been used to measure fluorescence of drugs in tissue. This study was designed to determine if in-vivo fluorescence intensities could be correlated with tissue concentration of chloroaluminum phthalocyanine tetrasulfonate in rat tissues. Following LIF measurement, the animals were euthanized and the concentration of AlPcs in different tissues were determined using chemical extraction technique. In-vivo fluorescence intensities were correlated with the extracted AlPcs for several tissues. A linear relationship between concentration and in-vivo fluorescence intensity was found for all tissues examined with correlation coefficient being highest in tissues such as liver, spleen, kidney and tumor. The correlation coefficient in skin, leg muscle and tongue was lower.

Treatment of spontaneously occurring veterinary tumors with photodynamic therapy

Chloroaluminum phthalocyanine tetrasulfonate was administered intravenously (1.0 mg/kg) to client owned cats and a dog with spontaneously occurring squamous cell carcinoma of head and neck. Light was delivered 48 hours post injection of the photosensitizer. An argon- pumped dye-laser was used to illuminate the lesions with 675 nm light delivered through a microlens fiber and/or a cylindrical diffuser. The light dose was 100 J/cm2 superficially or 300 J/cm interstitially. Eleven photodynamic therapy treatments in seven cats and one dog were performed. Two cats received a second treatment in approximately sixty days after the initial treatment. The superficial dose of light was increased to 200 J/cm2 for the second treatment. While the longest follow-up is twelve months, the responses are encouraging. The dog had a complete response. Among the cats, three showed complete response, three showed partial response and one showed no response. One cat expired two days post treatment. It is early to evaluate the response in two cats that received second treatments. Photodynamic therapy with chloroaluminum phthalocyanine tetrasulfonate was effective in treating squamous cell carcinoma in pet animals.

Balloon photodynamic therapy of esophageal cancer: effect of increasing balloon size

We have found that an esophageal centering balloon improves light delivery to esophageal mucosa during photodynamic therapy (PDT). However, balloon pressure on esophageal mucosa could possibly reduce mucosal blood flow and oxygenation, therefore reducing the photodynamic therapy effect. Studies were performed in the canine esophagus of 10 animals to investigate whether increasing the size of the centering balloon and hence the pressure on esophageal mucosa would alter the tissue effect of PDT. It was concluded that increasing balloon size resulted in reduced tissue damage when mucosal equivalent light dose was administered during photodynamic therapy. Proper sizing of centering balloons will be necessary for balloon PDT of esophageal mucosal dysplasia or cancer.