Comparison of intra-luminal versus intra-tumoural temperature measurements in patients with locally advanced prostate cancer treated with the coaxial TEM system: report of a feasibility study

Abstract

A study was performed on regional hyperthermia for patients with locally advanced prostate carcinoma. The primary objective was to analyse the thermometry data with an emphasis on the possibility of replacing invasive thermometry by tumour-related intra-luminal thermometry. Fourteen patients were treated with a combination of conformal external beam radiotherapy (70 Gy) and hyperthermia. Hyperthermia was delivered using the Coaxial TEM system, one treatment per week, to a total of five treatments. Thermometry was performed in bladder, urethra, rectum and esophagus. Invasive thermometry in the prostate was carried out during one or two treatments for each patient by placing transperineally a central and a peripheral catheter. Heterogeneous temperature distributions were measured in the prostate. The mean average invasive temperature range was 1.1 degrees C. Due to the temperature heterogeneity and a limited number of thermometry sensors (mean 7, range 2-13), large variability between treatments and patients existed regarding achieved temperatures and dose. The mean invasive T90 was 40.2 +/- 0.6 degrees C and T50 was 40.8 +/- 0.6 degrees C. The mean Cum min T90>40.5 degrees C per treatment was 22 (range 0-50). Importantly, intra-luminal temperatures did not reliably predict invasively measured temperatures. Invasive thermometry, therefore, remains compulsory to calculate a thermal dose for an individual patient. Changes in temperature during treatment, measured by the urethral sensors, corresponded well with changes in temperature measured by the individual invasive sensors. Similar comparison of rectal temperature changes with intra-prostatic temperature changes was not as predictive. The similarity in temperature changes between the urethral and interstial sites, suggests that urethral temperatures are sufficient for treatment optimization. The SAR profile did not correspond with the temperature profile indicating heterogeneous perfusion. Although regional hyperthermia in combination with external beam radiotherapy for locally advanced prostate carcinoma is clinically feasible, the question on the importance of invasive thermometry remains.

Conformal radiotherapy plus local hyperthermia in patients affected by locally advanced high risk prostate cancer: Preliminary results of a prospective phase II study

“…The use of LHT could avoid the hazard of radiotherapy dose escalation, which increases grade 2-3 rectal complications from 12% to 26% when the total dose is increased from 70 to 78 Gy [16]. The possibility to omit invasive thermometry in prostate cancer is still uncertain, and if a thermal dose in the individual patient is required, an invasive measurement will be needed [17]. Nevertheless, in many tumours a strong correlation exists between endoluminal and invasive thermometry [18] and similarly in prostate cancer a non-invasive measurement could replace the intratumoural thermometry [11].…”

Clinical hyperthermia of prostate cancer using magnetic nanoparticles: Presentation of a new interstitial technique

“…In fact, the results of several studies evaluating thermoradiotherapy of locally advanced or androgen-independent prostate cancer are certainly better than would be expected if only irradiation had been administered, although evidence to prove this in the form of phase III studies is not available. Invasive and non-invasive thermometry during regional hyperthermia of the prostate has been investigated in some detail [17,18]. It was found that temperature distribution in the prostate is heterogeneous and intra-luminal measurements tend to over-estimate the actual temperatures achieved in the prostate during hyperthermia.…”

On verification of hyperthermia treatment planning for cervical carcinoma patients

“…In this study, thermocouple thermometry was used, which has been proven to provide reliable temperature information when good thermal contact with the tissue is ensured [27,[38][39][40]. For some cases the thermal contact between thermocouples and tissue was suboptimal, causing artefacts in the ÁT measurements, resulting in very high ÁT meas due to self-heating of the thermocouple probes [37].…”