Lasers: reflections on their evolution.

A review of the past 22 years of laser applications shows that a great deal of progress has been made. It allows one to see the evolution of laser therapy, compare it with other modalities used in surgical oncology, and identify certain program that merit clinical trial. Use of lasers in surgical oncology began with a laser knife. Tissues were divided and removed with the focused beam of the CO2 laser, which replaced the scalpel previously used to perform surgical procedures. Later, the Nd:YAG laser was used in hollow visci such as the trachea and esophagus to open obstructed passages and possibly to cure many cancers. The operating microscope was used in the larynx to remove benign and malignant lesions, and for obstructing lesions to provide time to treat medical complications by reopening airway passages, and to add irradiation and/or chemotherapy preoperatively. Many times the Nd:YAG laser was used gastroscopically to treat bleeding or obstruction. Cytoreduction by laser made surgery or chemotherapy, or both, plausible. Addition of the sapphire tip and, later, the bare of sculptured fiber increased the variety of procedures possible with the Nd:YAG laser. Photodynamic therapy (PDT) uses various drugs that are localized in cancer cells. The cancer is then destroyed by laser emissions of the proper wavelength. One of the problems with PDT is getting the light to the tumor. Preactivation is addressed in this report. The problems associated with anaerobic tumors are discussed and suggestions for clinical trials offered. Laser hyperthermia is compared with induced hyperthermia as well as in combination with irradiation. Protocols of local laser hyperthermia combined with irradiation need further exploration. This review addresses the use of lasers in the destruction of tumor cells for bone marrow transplant and several old and new experiments used to block the AIDS virus. Finally, ongoing research is discussed, including the present and future roles of lasers.