Further Justification for Development of Non-Invasive Thermometry

Abstract

In this issue of the journal, the article by Ren et al. ‘A pilot study of intracavitary hyperthermia combined with radiation in the treatment of esophageal carcinoma’ presents results of a pilot study in which 25 patients were treated with an intracavitary microwave applicator for esophageal carcinoma. These treatments were given in combination with external beam radiation and intraluminal radiation. Hyperthermia was applied for 1 h before and after the intraluminal radiation procedure. Although the response rate in this series of patients was relatively good, the long term control rates did not appear to be any better than historical controls for radiation alone. Based on the low level of toxicities reported, however, the authors have suggested that this method is reasonable to consider for further clinical investigation.

The real issue in interpreting the data presented in this paper relates to the fact that there is no intratumoral thermometry. As has been well established in other tumor sites, thermometric data is strongly correlated with treatment outcome. In the case where clinical results do not favour the use of hyperthermia compared with historical controls, one is left wondering whether the lack of improvement in control is due to inadequate heating. This is known to have been the case in several large clinical trials. Because no intratumoral thermometry was obtained in this series we cannot ascertain whether this was the fact or not. There is a significant challenge to providing intratumoral thermometry for sites such as the esophagus, and we have elected to publish the paper acknowledging this difficulty. Thus, it is possible that additional information on intraluminal temperatures could have provided some insight as to why some patients fared better than others in the series.

However, even intraluminal temperatures are not a long term answer to this dilemma. If we are to move forward into the treatment of deep-seated malignancies, many of which are difficult or impossible to instrument with thermometric probes, we must emphasize further development of non-invasive thermometry. Significant strides in this arena have been made particularly using technologies such as magnetic resonance imaging. We encourage investigators involved in this area to continue this work which is vitally important to the continued development of hyperthermia.