Methods and clinical results of interstitial thermoradiotherapy

Besides percutaneous hyperthermia techniques, some new interstitial procedures have been developed and included into the arsenal of radiotherapists. As compared to percutaneous techniques, considerable benefits are offered by interstitial methods: a more homogeneous distribution of therapeutical temperatures, a better sparing of normal tissue, the possibility to treat deep tumors, and better therapy control and evaluation by extensive "thermal mapping" within the target volume. This study presents the technical principles and the clinical possibilities of the interstitial hyperthermia methods developed hitherto: resistive radiofrequency hyperthermia, radiative microwave hyperthermia, inductive ferromagnetic seed hyperthermia, and conductive hot-water perfusion hyperthermia. Until now, interstitial thermo-radiotherapy was only performed during some phase I/II studies. It was applied for palliative reasons in persisting and recurrent tumors accessible for implantation and situated in superficial to semi-deep locations with no or insufficient response to differently combined treatment modalities (surgery, radiotherapy, or chemotherapy). The preliminary clinical results obtained in almost 300 patients are quite promising: complete remission rates up to 70% have been achieved. Interstitial hyperthermia represents an effective and safe therapy modality, especially when combined with radiotherapy in palliative tumor therapy. At present, several prospective randomized multicentric studies are conducted to investigate its value as adjuvant therapy modality.