The role of interstitial therapy in present day radiotherapy

The role of interstitial therapy in the treatment of malignant tumors is discussed. With interstitial therapy, the tumor is accurately localized under general anesthesia, irradiation is limited to the tumor-bearing volume of tissues with minimal irradiation of normal structures, and treatment time is shorter than with external beam therapy. Disadvantages include its rather limited clinical application, more complicated dosimetry, the higher level of technical skill required in the surgical procedure, and radiation exposure of operator and personnel. Interstitial therapy is indicated for relatively small well differentiated primary tumors and in cases where the primary and lymph node metastases are in close proximity. A combination of interstitial and external beam therapy is recommended for advanced tumors and in cases of unsatisfactory implants. Seven illustrative cases are presented. It is recommended that improved afterloading techniques and surgical and nonsurgical procedures (e.g.,suspension laryngoscope) be developed so that this type of therapy can be extended to all cases requiring high doses and a small volume of radiation.