Clinical evaluation of short-life radioactive source Au-198 grain

Au-198 grain has been used as a new source in brachytherapy instead of Rn-seed since September 1975 in Japan. A total of 60 cases with malignant tumors of the oral cavity treated with Au-198 grain during the period of September 1975 to November 1978 were analyzed. Nineteen cases were treated with Au-198 grain alone, twenty-nine were with combined external beam therapy and the other twelve were treated as a boost implant for Radium needles or as a recurrent disease. Two-year local recurrence free rates were 78% (7/9) by Au-198 grain alone and 67% (10/15) by Au-198 grain combined with external beam therapy. The frequency of local necrosis following the combined therapy was inevitably higher than Au-198 grain alone. However, these results were somewhat better than the results obtained from treatment of tongue cancer using Rn seed with or without external beam which reported previously. An analysis was also made of the local condition of the treated area applying with the TDF values. A suitable permanent implant dose of Au-198 grain might be slightly lower than Rn seed considering from the TDF value analysis. The Au-198 grain technique seemed to be an excellent choice of treatment as far as the lesion was small or superficial enough, or the lesion was locating in the sites anatomically to be not able to apply Radium needles. The technique has also an advantage to be applicable without severe discomfort to the patient and less exposure to the operator compared to the Radium needle technique. (author)