N3 (TNM-UICC) metastatic neck nodes managed by combined radiation therapy and hyperthermia: clinical results and analysis of treatment parameters.

In an attempt to improve the control of N3 (TNM-UICC) fixed and inoperable metastatic nodes, local microwave hyperthermia (HT) was combined with radiation therapy (RT). From February 1981 to January 1985, 34 patients, with N3 metastatic nodes from primary tumours in the head and neck, were treated according to two different prospective, non-randomized protocols: 23 patients received HT combined with the first course of conventionally fractionated radical RT (40 Gy + HT--2 week interval--20-30 Gy), and 11 patients received HT combined with palliative RT (20-50 Gy + HT). All the patients were treated with the same microwave applicator (MA-150) on the BSD-1000 unit, at a frequency of 280-300 MHz. Temperatures were measured by means of 2-3 Bowman probes placed within the tumour (core and periphery) and 5-6 probes on the skin surface. HT sessions were delivered after RT (less than 20 min), 2 or 3 times weekly, for a duration of 30 min after steady-state temperatures were obtained. Twenty-seven patients out of 34 were evaluable, with a follow-up of at least 3 months (range 3-39 months; median 10 months). Clinical results at 3 months revealed 59 per cent complete responses, 30 per cent partial responses, and 11 per cent with progressive disease. Analyses of response rates showed: a marginally significant difference (P = 0.095) between RT alone (historical control) and the entire group of patients treated with RT plus HT; a significant difference (P = 0.034) if RT alone is compared with Protocol A (RT greater than or equal to 60 Gy + HT); no significant difference between the two protocols employing HT, despite the different RT doses utilized; no significant differences in response rates, as a function of minimal intratumoural temperatures achieved, number of weekly HT sessions or total number of HT sessions; and a significantly lower response rate for nodes with maximum diameter greater than 6 cm (P = 0.043). No important differences in acute side effects between irradiated and heated regions in the same patient were noted. Late side effects in patients treated with RT plus HT included three cases (9 per cent) of severe fibrosis, possibly as a consequence of excessive maximum tumour temperature (greater than 46 degrees C).