The destiny of brachytherapy in oncology

At the invitation of the American Radium Society, Pierquin reviews his very large experience with continuous low dose rate irradiation of cancer. The target volume is treated with 6,000-7,000 rad in 3-10 days at a dose rate of 30-100 rad/hr. Preference for continuous low dose rate irradiation is based on the earlier work of Jean Pierquin, Georges Richard, Claudius Regaud, and Ralston Paterson with radium sources. Afterloading techniques with iridium-192 have been substituted allowing safer and more precise placement. An accumulated experience with 5,000 patients over the past 15 years permits conclusions that the techniques are safe, easy, inexpensive, and effective for tumors accessible to direct instrumentation. Dosimetry is based on the Paris system. Standardizing upon a dose of 7,000 rad, Pierquin concludes there is an isoeffect of continuous radiation at low dose rates of 25-100 rad/hr. The differential effect on tumor versus healthy tissue is impressive even when large volumes are irradiated, as in neck adenopathy. Stemming from this experience, three trials have been carried out of low dose rate teletherapy with cobalt-60 sources in oral cavity and oropharynx tumors, delivering 7,000 rad at rates of 90-100 rad/hr. Pierquin hopes for the same very high local control rates (in the order of 95%)achieved by iridium-192 endoradiotherapy of accessible T1, T2, T3, and T4 cancers.