RF-power and temperature data analysis of 444 patients with primary cervical cancer: deep hyperthermia using the Sigma-60 applicator is reproducible

Abstract

Treatment reproducibility is important to guarantee reproducible treatment-outcome, a low-complication rate and efficient treatment procedures. This study evaluated the performance of loco-regional deep hyperthermia with four BSD-2000 configurations during 1990-2005 using the direct available parameters, i.e., temperature and power. Primary cervical cancer patients (n = 444) were all treated within the Sigma-60. Patients were grouped in three weight-groups: <61 kg, 61-70 kg, >70 kg. Different temperature and power indices were extensively analyzed per BSD configuration, per weight-group, and over the time-period. No substantial variations were found for temperature/power indices over the four BSD configurations or for the temperature doses in similar weight-groups. The 'bare' power indices were increased with weight; however, the derivative power-related (W/kg, W/cm(2)) and temperature indices decreased. Large variations were found in the power-related parameters during 1991-1996 (1st time-period), whereas they were much smaller during 1997-2005 (2nd time-period). The most relevant change noted was the adaptation of the treatment strategy with respect to power modulation. The average frequency of switched-off was 3.4 and 8.9 times/treatment session for the 1st and 2nd time-period, respectively, while the average duration of each switched-off time was 78.2 vs. 38.3 s. The yearly average of vagina T(50) was in the range of 39.3-40.2 degrees C (1st time-period) and 40.0-40.5 degrees C (2nd time-period). In 40% of the patients, a positive correlation was found between normalized net integrated power per pelvic area and vagina T(50). Good reproducible heating is achieved with the BSD-2000 Sigma-60 irrespective of the regular technological upgrades of the system and variation of trained staff-members.