Interstitial hyperthermia using self-regulating thermoseeds combined with conformal radiation therapy

The combination of hyperthermia and radiation in the treatment of malignancies is based on a variety of experimental data which have proven the synergistic effects of these two treatment modalities. We planned a phase II trial in a special hyperthermia research group (SFB 273) of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) to determine feasibility, acute toxicity and efficacy of this combination for prostate cancer.

A total of 57 patients with localized prostate cancer were treated with interstitial hyperthermia using cobalt-palladium thermoseeds and conformal radiation between July 1997 and December 2000. Thermoseeds were placed into the prostate homogeneously. Hyperthermia was created using a magnetic field and was delivered in six sessions once weekly. 3D-conformal radiotherapy of 68.4Gy was given simultaneously in daily fractions of 1.8Gy.

Intra-prostatic temperatures were between 42 and 46 degrees C. No major side effects were observed during hyperthermia. Median follow-up was 12 months (range: 3-26 months). Median prostate specific antigen (PSA) value decreased from 11.6 to 2.4 ng/ml 3 months after treatment, to 1.3ng/ml 12 months after treatment and to 0.55 ng/ml 2 years after the therapy.

Interstitial hyperthermia is feasible, well tolerated and led to a steep decrease of PSA values. Our current follow-up is too short to comment about efficacy. Combining effective interstitial hyperthermia with conformal radiotherapy may be an exciting innovative treatment option for prostate cancer.