[Results of thermoradiotherapy of deep-seated tumors and problems in the evaluating its effects]

The results of thermoradiotherapy for deep-seated tumors indicated that 15% of the affected patients achieved CR and that the response rate (CR plus PR) was 58%. However, in some of the tumors which did not regress sufficiently, no regrowth was observed during follow-up. Furthermore, post-treatment CT scan revealed low-density areas occupying as much as 80% of the tumor area in 4 of 13 PRb tumors and 5 of 15 NRs. The appearance of these remarkable low-density areas on CT might be specific to thermotherapy, since it is uncommon following radiation therapy alone. Fifteen PR or NR tumors were resected and subjected to histopathological examination. It was found that cancer cells remained mainly in the tumor periphery in 12 of the 15 tumors while none were present throughout the entire tumor in the remaining 3 (2 PRbs and one NR). It was concluded from these results that it was possible to achieve local tumor control following thermoradiotherapy not only in CR tumors but also in some PRs or NRs which might remain unchanged in size but show prominent low-density areas on CT scan during follow-up. Accordingly, this suggests that the effects of thermoradiotherapy for deep-seated tumors should be evaluated on the basis of not only tumor regression but also the appearance of these low-density areas on post-treatment CT.