Dan J. Castro

Effects of the Nd:YAG laser on DNA synthesis and collagen production in human skin fibroblast cultures

Human skin fibroblasts were subjected to treatment with a Neodymium:YAG laser at 1060 nm with varying levels of energy determined by a reproducible method of dosimetry. DNA synthesis in the cells was measured by the incorporation of [3H]thymidine, and collagen production was monitored by the synthesis of nondialyzable [3H]hydmxyprohne after incubation of cells with [3H]proline. Using energy levels equal to 1.7 × 103 l/cm2, a significant reduction in DNA synthesis was noted, while the cells remained viable as tested by the trypan blue exclusion lest. With energy levels higher or equal to 2.3 × 10 l/cm2, the suppression of DNA synthesis was accompanied by cell nonviability. The collagen production, when measured immediately following the treatment with 1.7 × 103 l/cm2, was markedly reduced, and similar effects were observed with higher energy levels. However, when the cells were tested for collagen production at 20 hours following laser treatment, there was a significant decrease in collagen production at energy levels as low as 1.1 × 103 l/cm2, a dose that did not affect DNA synthesis or cell viability. Thus, the results indicate that the Nd:YAG laser can selectively suppress collagen production without affecting cell proliferation. These observations suggest that laser treatment could potentially be used to reduce collagen deposition in conditions such as keloids and hyperlrophic scars.

Metastatic head and neck malignancy treated using MRI guided interstitial laser phototherapy: An initial case report

Interstitial laser phototherapy (ILP) guided by magnetic resonance imaging (MRI) may become an attractive adjunctive modality for the treatment of deep and surgically inaccessible tumors of the head and neck when accurate methods of laser dosimetry and “real‐time” monitoring techniques with the MRI are introduced. We recently demonstrated in ex vivo and in vivo models, a linear relationship between levels of laser energies, thermal profiles, MR signal intensity changes, and histopathological tissue damage. Results of treatment in a patient with an unresectable large right jugulodigastric metastatic squamous carcinoma using new approach of MRI guided ILP are now reported. The patient complained of significant right‐sided neck pain and headaches secondary to a rapidly growing metastatic lymphadenopathy which recurred after previous surgery, radiation, and chemotherapy. Two treatment sessions were used at an interval of 2 weeks. Each treatment was performed in the MRI suite under heavy sedation. Using a 600‐μm bare fiber of the Nd:YAG laser implanted interstitially under MR guidance, the metastatic node was treated at three sites. T1‐ and T2‐weighted images were performed prior to, immediately after, 24 and 48 hours, and 4, 5, 7, 9, 16, and 25 days post‐treatment. Successful relief of pain and growth arrest of this node was observed after the second treatment and at the 3‐month follow‐up. These results demonstrate that this technique of ILP guided by MRI may be feasible in humans, and will become clinically practical when appropriate methods of dosimetry and instrumentation are developed.

Nd:YAG interstitial laser phototherapy guided by magnetic resonance imaging in an ex vivo model: Dosimetry of laser-MR-tissue interaction

Interstitial laser phototherapy (ILP) is a promising technique in which laser energy is delivered percutaneously to various depths of tumors. This technique will become clinically useful only when efficient, sensitive, and noninvasive monitoring systems are developed. In this study, the spatial distribution of ILP in bovine liver tissue, induced by a Nd: YAG laser with an interstitial sapphire-frosted contact probe, was evaluated by magnetic resonance imaging (MRI). Tissue was exposed to three energy densities of the Nd:YAG laser by a reproducible method of dosimetry. Thermal profiles were measured with a probe inserted 5 mm from the laser tip. T1-weighted magnetic resonance images were taken after the laser exposure. Tissue specimens were then evaluated for standard quantification of laser-induced damages. A linear correlation between the level of laser energy, induced temperature change, lesion size on T1 magnetic resonance image, and volume of histological damage was observed. Further improvement of this technique of dosimetry in an in vivo model should allow the development of software for MRI which will correlate the above parameters and render this technique of ILP clinically useful.

Hypericin: A New Laser Phototargeting Agent for Human Cancer Cells†‡

Laser activation of anthracycline‐related drugs combines chemotherapy with photoablation for improved treatment. Hypericin, a structurally related anthraquinone, was tested for laser activation and cytotoxicity in human cancer cells. Viability of P3 squamous cell carcinoma cells incubated with 1 to 20μg/mL hypericin was reduced by more than 95% after 1 minute exposure at 4°C to an argon laser (514 nm, 5 W), a KTP‐532 laser (532 nm, 5 W), or a 20‐A xenon lamp. Viability was reduced over 90% in six human carcinoma, sarcoma, and melanoma cell lines by this combined treatment, but only trace toxicity was seen after separate exposure to hypericin or light alone. These results show that hypericin is a sensitive agent for phototherapy of human cancer cells in vitro and indicate that this drug may be useful for tumor targeting via minimally invasive imaging‐guided laser fiberoptics.

Hypericin uptake in rabbits and nude mice transplanted with human squamous cell carcinomas: study of a new sensitizer for laser phototherapy.

Tissue uptake and biodistribution of hypericin was measured in rabbits and in nu/nu mice xenografted with P3 human squamous cell carcinoma to assess the value of this dye as an in vivo sensitizer for laser photoinactivation of solid tumors. Hypericin has absorption maxima at 545 and 590 nm with a fluorescence emission peak at 640 nm in ethanol. Dye uptake after intravenous injection was tested at 4 and 24 hours in rabbit tissues by ethanol extraction and quantitative fluorescence spectrophotometry. Maximum dye levels were seen at 4 hours in most vascular organs with lung having fivefold higher uptake than spleen followed by liver, blood, and kidney. Mice were examined after 2, 4, 6, 8, and 24 hours and after 3 and 7 days for dye uptake. The peak concentration of hypericin in murine organs was reached at 4 hours with uptake per gram of tissue as follows: lung>spleen>liver>blood>kidney>heart>gut>tumor>stomach>skin>muscle>brain. Elimination of hypericin was rapid in most murine organs with residual dye under 10% of maximum by 7 days compared to 25% to 30% retention for the squamous cell tumors and several normal tissues. These results suggest that hypericin may be a useful photosensitizer for KTP/532 laser interstitial therapy of human cancer.

Wound healing: biological effects of Nd:YAG laser on collagen metabolism in pig skin in comparison to thermal burn

Pig skin was treated with the Nd:YAG laser at 1,060 nm or electrocautery, at energy densities of 649 ± 20 J/cm2 and 612 J/cm2, respectively. Biopsies of treated areas and of normal skin were performed at 7, 14, and 60 days after treatment and processed for histology, electron microscopy and biochemical assays. Wound healing, as shown histologically, was similar in both treated groups. Depth of injury appeared to reach reticular dermis at day 7 in each treated group. However, thermal burn was more destructive of regular collagen, whereas the laser appeared to damage deep dermal blood vessels without destroying surrounding connective tissue. Biochemical assays revealed increased collagen production and increased collagenolytic activity 7 days after laser injury. However, by day 60, there was a reduction in total collagen content in laser treated skin below that of normal skin, which correlated with decreased collagen synthesis and unchanged collagenolytic activity. In burn specimens there was an initial decrease in total collagen content which reverted to normal by day 60. Active collagen degradation occurred at all 3 time points, but a marked increase in synthetic activity occurred as the burn scar was laid down. Laser treatment resulted in reduction of the amount of collagen below that in burn scarred or normal skin, suggesting that classical scar formation may be inhibited. These results indicate that the Nd:YAG laser may be useful for the treatment of keloids and hypertrophic scars.

Intratumoral hypericin and KTP laser therapy for transplanted squamous cell carcinoma.

Objectives/Hypothesis To test intratumoral photodynamic therapy (IPDT) as a new treatment for squamous cell carcinoma in a preclinical tumor model.

Importance of iron repletion in the management of Plummer-Vinson syndrome.

Plummer-Vinson syndrome (PVS) is characterized by iron deficiency anemia, upper esophageal stricture, cervical dysphagia, and glossitis. The precise role of iron deficiency in PVS has yet to be defined and remains a subject of much debate. A 29-year-old woman with PVS is presented. The patient had a 4-year history of severe iron deficiency anemia, a 2-year history of progressive dysphagia and weight loss, and a greater than 90% benign upper esophageal stricture. Iron therapy alone resolved her dysphagia and anemia, and a follow-up esophagram 1 year later showed a residual stenosis of less than 30%. The development of severe iron deficiency anemia in this patient 2 years before the onset of dysphagia, as well as the response of the stricture to iron repletion, supports the theory that iron deficiency can cause dysphagia and upper esophageal strictures. The occurrence of glossitis, gastritis, and esophagitis in iron deficiency demonstrates the adverse effects of iron depletion on the rapidly proliferating cells of the upper alimentary tract.

Intratumoral cisplatin/epinephrine gel in advanced head and neck cancer: A multicenter, randomized, double‐blind, phase III study in North America

The objective was to evaluate the efficacy and safety of a novel intratumoral cisplatin/epinephrine injectable gel (CDDP/epi gel) for local control and palliation of tumor‐related symptoms in patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC).

Interventional Magnetic Resonance Imaging in the Head and Neck

Interventional MRI is clearly in its early stages of development. While the value of MR-guided aspiration cytology and MR evaluation of deep electrode implantation in the brain has already been confirmed with human clinical studies, the future of MR-guided interstitial laser therapy remains to be proven. Despite this, as we look ahead into the 1990s and the millennium, it is possible to imagine dedicated MR laser therapy units for combined radiological and surgical outpatient approaches in what may become the operating rooms of the 21st century.