Hematoporphyrin derivative photoradiation therapy for the treatment of intraocular tumors: examination of acute normal ocular tissue toxicity.

Preclinical studies designed to define potential side effects resulting from the use of hematoporphyrin derivative (HPD) photoradiation therapy (PRT) as a modality for treating intraocular tumors have been performed. Pigmented rabbits were used to evaluate acute normal ocular tissue toxicity following single HPD PRT treatments in which the light was directed through the pupil and onto a 1-sq cm area of the retina. The treatment procedure consisted of the i.v. administration of HPD (1 to 10 mg/kg) followed 48 hr later by a 15-min exposure of localized red light [635 +/- 5 nm; 40 to 400 milliwatts/sq cm] generated by a free running rhodamine B dye laser pumped by a 5-watt argon laser. Toxicity to normal retinal tissue was documented using fundus photography, fluorescein angiography, and histological examination. The results of this study demonstrated that ocular damage in the form of retinal edema, detachment, and necrosis could be induced by clinically relevant doses of HPD PRT. The area of retinal damage was limited to the treatment field in all but the highest doses of HPD PRT. The histological results were in agreement with the visual observations in that abrupt and demarcated transition areas between injured and normal-appearing retina were observed. Care will have to be used in the delivery of light to the treatment field if HPD PRT is to be utilized for treatment of intraocular tumors.

Fluorescence bronchoscopy for detection of lung cancer.

A system using the fluorescence bronchoscope has been designed for localization of small, early bronchogenic carcinoma by the fluorescence of previously injected hematoporphyrin derivative. The system included a 200W mercury vapor lamp and primary filter, flexible fiberoptic bronchoscope with special violet-transmitting light conductor, secondary filter, and image intensifier tube. Tests indicated the system could detect a tumor only 100 micron thick at the expected concentration of hematoporphyrin derivative: 1 microgram/gm at 48 to 96 hours following intravenous injection at a dosage of 2.5 mg/kg. Examination of resected specimens (six of lung, one of esophagus) showed positive fluorescence in all cases, with fluorescence visible beyond the region visible under conventional white light examination. Fluorescence bronchoscopy has been performed on four patients thus far. Positive fluorescence was observed in all three cases where the tumor had been known to occur. Positive fluorescence was also observed in the patient with sputum positive for lung cancer, but negative x-ray film findings. However, additional examinations are required to demonstrate the smallest lesion that can be detected in vivo.

Dosimetry considerations in phototherapy.

Dosimetry in phototherapy involves a determination of the energy absorbed per unit mass of tissue, corrected for the quantum yield in a photochemical reaction. The dose rate in photochemotherapy of cancer with hematoporphyrin derivative and visible light is related to the extinction coefficient, quantum yield for singlet oxygen production, concentration of sensitizer and energy flux density at depth. Data or methods of determining these quantities are presented. Calculations have been performed for the energy flux density at depth, as a function of the total attenuation coefficient and ratio of scattering coefficient to total attenuation coefficient, for isotropic scattering in slab geometry. For small absorption, these depth dose curves exhibit a maximum within the tissue followed by an exponential decrease.

Fluorometer for endoscopic diagnosis of tumors.

A filter fluorometer suitable for endoscopic applications has been developed for detection and characterization of superficial tumors by the fluorescence of a previously injected, tumor-specific agent, hematoporphyrin derivative. Fluorescence is excited by violet light conducted through a fiberoptic lightguide in the endoscope, and the fluorescence emission together with reflected violet are collected by another fiberoptic lightguide. The red fluorescence and violet are separated by a dichroic mirror and filter and detected in photomultiplier tubes. The ratio of the fluorescence signal to the reflected violet signal is proportional to the ratio of the fluorescence yield to the violet reflectivity but is insensitive to variations in distance, angle, and violet power. The instrument may be useful for localizing small tumors, and for quantitative measurements of the amount of hematoporphyrin derivative in the tumor, a requirement for accurate dosimetry in photoradiation therapy.

Temperature rise during photoradiation therapy of malignant tumors.

This report discusses the optical and thermal distribution during photoradiation therapy of malignant tumors. Emphasis is put on the therapeutic procedure with the light dose delivered through an inserted optical fiber. Theoretical predictions and experimental results indicate that the temperature rise during the procedure may give rise to hyperthermal cell kill. The report discusses the extent of the regions with hyperthermal bioeffects in terms of tissue parameters as optical absorption and scattering, thermal conductivity, specific heat, blood flow, and optical dose parameters as optical power and exposure time.

Laser fluorescence bronchoscope for localization of occult lung tumors.

A system for imaging occult bronchogenic carcinoma by the fluorescence of previously-injected, tumor-specific compound hematoporphyrin-derivative has been assembled and successfully used to locate a tumor 1 mm thick. The violet excitation source is a krypton ion laser coupled to fused quartz fiber light conductor. An electrostatic image intensifier attached to a standard flexible fiberoptic bronchoscope provides a bright image even at relatively low irradiance. A red secondary filter rejects most reflected background and autofluorescence. Sensitivity and contrast capability of the system should permit detection of a tumor less than 0.1 mm thick.

Fluorescence bronchoscopy for localization of carcinoma in situ.

A fluorescence bronchoscope system has been developed for imaging lung tumors by fluorescence of a previously injected, tumor-specific agent hematoporphyrin derivative. Carcinoma in situ has been localized, but there are too many false positives and negatives. A new system has been implemented which allows rapid switching between viewing of fluorescence, and viewing of the same area under white light illumination as in conventional bronchoscopy. The excitation source is a violet krypton ion laser coupled to a fused quartz fiber light conductor, with a diverging microlens to spread the light uniformly. A third-generation, microchannel plate image intensifier amplifies the weak fluorescence for viewing and video display, recording, and analysis. A movable mirror and periscope bypasses the intensifier for normal color viewing and video display and recording, with the laser shutter closed and the white light shutter open. This facilitates accurate localization, comparison of the color and fluorescence images, and precise sampling during biopsy. The improved system should reduce the false positive rate due to biopsy sampling error, and together with the video analyzer should reduce indeterminate results.

Photoradiation therapy of endobronchial lung cancer. Large obstructing tumors, nonobstructing tumors, and early-stage bronchial cancer lesions.

Photoradiation (photodynamic) therapy of endobronchial primary and metastatic lung cancers uniformly results in a complete response--that is, the opening up of totally or partially obstructed bronchi to their walls. The method, employing hematoporphyrin derivative and red laser light from an argon-pumped dye laser, is safe, efficient, and effective. The safety and lack on any complications rest upon the use of light-diffusing cylinder tips, and upon clean-up bronchoscopy to remove tumor debris promptly. The trachea and main and lobar bronchi, as well as segmental and subsegmental bronchi, can be entirely freed of tumor and completely opened up.

Laser instrumentation and safety.

A review of the operation principles of lasers and the various types used in chest medicine is given. This includes CO2, Nd:YAG, argon, krypton, and dye lasers. Safety considerations in the use of lasers are also outlined.

A feasibility study of the use of fluorescence bronchoscopy for localization of small lung tumours.

The possible use of fluorescence bronchoscopy for localization of bronchogenic tumours at the carcinoma in situ stage has been investigated. The target lesion is 80 micrometer thick with a mass of 250 microgram, containing 250 pg of haematoporphyrin derivative. The injected haematoporphyrin-derivative is preferentially taken up or retained by a malignant tumour, and can be detected in small amounts by its red flourescence under illumination by violet light. Previous clincial trials were successful in detecting tumours, but the instrumentation was only marginally adequate, the fluorescent compound was not standardized and no measurements or calculation of sensitivity were made. In this work, a fibreoptic bronchoscope system with a 200 W mercury vapour lamp, special violet-transmitting light conductor, sharp cut-off blue and red filters and three-stage image intensifier tube was designed and assembled. Measurements in vitro indicate the design objectives were met, and test on tumours are in progress.

Hematoporphyrin derivative photoradiation induced damage to normal and tumor tissue of the pigmented rabbit eye.

Cytotoxicity induced by hematoporphyrin derivative (HpD) photoradiation in both normal and experimental tumor tissue of pigmented rabbit eyes has been examined. In addition, documentation of HpD induced fluorescence in ocular structures has also been obtained. Acute normal ocular tissue toxicity studies demonstrated that HpD (1-10 mg HpD/kg) followed 48 hours later by a transpupil irradiation of red light (635 nm, 36-90 J/cm2) resulted in demarcated areas of retinal damage. Long term (chronic) toxicity studies have shown that the initial damage to the retina was permanent but that no damage to the cornea, lens or vitreous could be observed during a 16 month follow-up. Visual and histological documentation have been obtained, following HpD photoradiation therapy (PRT), in rabbit eyes having heterotransplanted single nodule amelanotic melanomas. A toxic effect characterized by tumor blanching, edema and hemorrhage was observed within 24 hours of treatment. Histological examination obtained 24 hours following HpD PRT illustrated massive tumor tissue necrosis and vascular disruption. HpD PRT at clinically relevant doses was also shown to be effective in selectively curing the highly malignant amelanotic iris melanoma. It is concluded that HpD PRT may prove to be an effective modality for treating certain ocular tumors.

Treatment of vascular lesions with a CW yellow dye laser--initial trials.

Thirteen patients with vascular lesions were treated with a CW yellow dye laser. Most of these patients were either poor candidates for argon laser treatment (ALT) or had undergone unsuccessful argon laser treatment. Twelve patients responded with a "desirable" treatment result. One patient did not respond adequately to have his result classified as "desirable," though all patients experienced fading of their lesions. None of the patients experienced scarring, epidermal thinning, or hypopigmentation. This lack of complications, associated with an incidence of desirable results in twelve of the thirteen patients, is noteworthy because all but one of the patients with portwine stain had difficult-to-treat lesions whose treatment is not attempted by many ALT centers. We believe that yellow light has certain advantages over blue-green argon laser light for the treatment of vascular lesions and think that further study is warranted.

Treatment of the transplantable FANFT induced bladder tumors with the purpurin SnET2 and red light emitted by a pulsed frequency doubled Nd:YAG laser.

Photodynamic therapy of transplantable N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide-induced tumors engrafted onto Fischer CDF (F-344)/CrlBR rats that had been sensitized with the photosensitizer tin (ll) etiopurpurin dichloride was performed in combination with visible light (approximately equal to 660 nm) emitted by either a continuous wave argon-dye laser or a pulsed, frequency-doubled Nd:Yag laser. Tumor control was assessed either by tumor dry-weight 12 days after treatment or by the palpatory absence of tumor at 60 days after treatment. Both laser sources were effective in creating the desired photodynamic effect. This study demonstrates the potential for the use of a solid-state pulsed laser for photodynamic therapy when used in combination with the tumor sensitizer tin (ll) etiopurpurin dichloride.

Photodynamic therapy for antifibrosis in a rabbit model of filtration surgery.

BACKGROUND AND OBJECTIVE: The purpose of this pilot study was to investigate the use of photodynamic therapy (PDT) using tin ethyl etiopurpurin (SnET2) as an adjunctive antifibrotic therapy for filtering surgery in a rabbit model. MATERIALS AND METHODS: The pharmacokinetics of SnET2 were established by intravenous (1 mg/kg) and subconjunctival (25, 50, or 75 micrograms) injections and compared with controls. Intravenous and subconjunctival SnET2 injections were given prior to posterior lip sclerectomies followed by postoperative laser irradiation (664 +/- 7 nm; 100 mW/cm2; 30 J/cm2). Antifibrotic efficacy was established by clinical response and histologic examination. RESULTS: After subconjunctival injections, large areas of avascular conjunctiva were produced and filtering bleb survival was prolonged. No effect was found for intravenously administered photosensitizer followed by light irradiation. CONCLUSIONS: PDT may be an alternative antifibrotic therapy for filtration surgery that does not use chemotherapeutic agents or ionizing radiation. Multiple parameters (light, drug dose, irradiation area) may be manipulated to improve predictability of the antifibrotic effect.

Photodynamic therapy for choriocapillaris using tin ethyl etiopurpurin (SnET2).

BACKGROUND AND OBJECTIVE: To investigate the use of photodynamic therapy (PDT) using tin ethyl etiopurpurin (SnET2) for occluding the choriocapillaris in the eyes of pigmented rabbits. MATERIALS AND METHODS: Following intravenous injection of SnET2 (0.5 and 1 mg/kg) or lipid emulsion alone, the fundus of pigmented rabbits (n = 21) was irradiated starting 15 to 45 minutes after photosensitizer injection using 664-nm light at a fluence of 300 mW/cm2 and light doses of 5 to 20 J/cm2. Funduscopy, fluorescein angiography, and light and electron microscopy were performed at 1, 14, and 28 days after PDT. RESULTS: Following SnET2 and PDT, closure of the choriocapillaris was achieved with light doses as low as 5 J/cm2 (17 seconds) and a drug dose of 0.5 mg/kg of SnET2. Vascular occlusion was documented by fluorescein angiography and histology. Photodynamic damage was noted in the choriocapillary endothelial cells. Retinal pigment epithelial damage and outer retinal damage were also observed. No funduscopic, angiographic, or histologic findings were present in the eyes of pigmented control rabbits. CONCLUSIONS: PDT with SnET2 was effective in this animal model, using low levels of activating light for the occlusion of the choriocapillaris. This has clinical implications for the treatment of choroidal neovascularization and could be a more selective therapy than thermal laser photocoagulation.

Photodynamic therapy of the ciliary body with tin ethyl etiopurpurin and tin octaethyl benzochlorin in pigmented rabbits.

BACKGROUND AND OBJECTIVES: The authors used a pigmented rabbit model to investigate two photosensitizers, tin ethyl etiopurpurin (SnET2) and tin octaethyl benzochlorin (BNZ 203), to determine their potential for creating ciliary body injuries during photodynamic therapy (PDT). MATERIALS AND METHODS: The biodistribution of SnET2 (n = 10) and BNZ 203 (n = 9) was studied by fluorescence microscopy using a low light detection system, based on charged-coupled device photography, with digital image processing at 1 and 24 hours after injection. PDT with SnET2 (n = 8; 664 +/- 7-nm light; 75 mW/cm2; 50 or 100 J/cm2; 1-mm spot size) and BNZ 203 (n = 6; 689 nm; 75 mW/cm2; 50 or 100 J/cm2; 1-mm spot size) was performed at 24 hours post-injection. The control subjects for SnET2 (n = 5) and BNZ 203 (n = 3) were given a maximal light dose (100 J/cm2). RESULTS: Both photosensitizers demonstrated an intravascular distribution at 1 hour that shifted to a ciliary body distribution at 24 hours (SnET2 much greater than BNZ 203). In addition, the SnET2 demonstrated suborgan localization to the nonpigmented ciliary body epithelium. Both photosensitizing agents were able to produce selective injury to the rabbit ciliary body (SnET2 much greater than BNZ 203), with evidence of a small component of thermal damage (SnET2 greater than BNZ 203). CONCLUSIONS: PDT with SnET2 or BNZ 203 can produce selective injury to the pigmented rabbit ciliary body. The nonpigmented ciliary body epithelium exhibits selective retention of SnET2. This finding warrants further investigation.