Hyperthermia–its actual role in radiation oncology. Part IV: Thermo-radiotherapy for malignant brain tumors
ABSTRACT
BACKGROUND: High-grade malignant gliomas have a dismal prognosis. Only achievement of long-term local control improves overall survival. Conventional treatments have not been successful, but thermoradiotherapy appears to be a promising new approach to this disease.
PATIENTS AND METHODS: The review addresses the various HT techniques applied for brain heating, the biological rationale and experimental studies supporting the use of heat in addition to radiotherapy for brain tumors. Normal brain damage exposed to heat is critically evaluated. Clinical trials implementing HT for tumors of the brain accumulating more than 400 patients are discussed.
RESULTS: HT is a feasible and effective approach to brain tumors. Important selection criteria are tumor size (< 6 cm) and location (supratentorial, peripheral). Acute treatment toxicity is relatively low and long-term side effects are similar to those observed for RT alone. In some studies a high response rate and improvement of survival was achieved. Tumor control and survival depend on histology (anaplastic astrocytoma vs. glioblastoma multiforme), extent of surgery (complete vs. incomplete), tumor status (primary vs. recurrent), age and performance status. Satisfactory heating also correlates significantly with favourable treatment outcome.
CONCLUSIONS: The encouraging results of clinical trials may be biased by favourable tumor and patient selection. Randomized clinical trials comparing RT alone versus combined RT-HT for advanced and recurrent brain tumors are justified. Part I has covered biological and technical fundamentals of clinical hyperthermia and has been published in Strahlenther. Onkol. 168 (1992), 183-190. Part II has covered clinical fundamentals and results in superficial tumors of clinical hyperthermia and has been published in Strahlenther. Onkol. 169 (1993), 633-654. Part III has covered clinical rationale and results in deep seated tumors and has been published in Strahlenther. Onkol. 171 (1995), 251-264.