INTERSTITIAL LASER HYPERTHERMIA MODEL DEVELOPMENT FOR MINIMALLY INVASIVE THERAPY OF BREAST-CARCINOMA

Background: This investigation describes the preclinical development o f a laser fiberoptic interstitial delivery system for the thermal dest ruction of small breast cancers. We propose adaptation of this technol ogy to stereotactic mammographic instrumentation currently employed fo r diagnostic core biopsy to thermally ablate a site of disease with ma ximal treatment efficacy minimal observable surficial change, reduced patient trauma, and lowered overall treatment costs. Study Design: Las er hyperthermia is a clinical modality that seeks to achieve tumor des truction through controlled tissue heating. The advantage of laser-ind uced hyperthermia over traditionally used heat sources such as ultraso und, microwave, or radiowave radiation lies in the ability to focus he at localization to the specific tumor tissue site. Neodymium:yttrium a luminum garnet (Nd:YAG) laser light transmitted through a fiberoptic c able to a diffusing quartz tip can induce such temperature increases l eading to localized tissue destruction. Because breast cancer occurs w ith greatest frequency in the mature woman whose breast tissue has und ergone glandular involution with fatty replacement, this study concent rates on determining the resultant laser energy heat distribution with in fat and fibrofatty tissue. This investigation studied the time-temp erature responses of ex vivo human breast and porcine fibrofatty tissu e, which led to an in vivo subcutaneous porcine model for the practica l demonstration of a laser hyperthermia treatment of small volumes of porcine mammary chain tissue. Results: Spatial recordings of the resul tant temperature fields through time exhibited similar, reproducible t hermal profiles in both ex vivo human breast and subcutaneous porcine fat. In vivo laser-produced temperature fields in porcine subcutaneous fat were comparable to those in the exvivo analyses, and showed a his tologically, sharply defined, and controllable volume of necrosis with no injury to adjacent tissues or to overlying skin. Conclusions: Inte rstitially placed, fiberoptically delivered Nd:YAG laser energy is cap able of controlled tissue denaturation to a defined volume for the tre atment of small breast cancers. It is hoped that this minimally invasi ve approach, with further investigation and refinement, may lead to th e effective treatment of small, well-defined breast cancers that are c ommonly diagnosed through stereographic mammography and stereotactic c ore biopsy. The juxtaposition of such a localized treatment modality w ith these increasingly used diagnostic tools is of considerable promis e. (C) 1998 by the American College of Surgeons.