ABSTRACT
BACKGROUND: Adequate tumor temperatures during hyperthermia are essential for good clinical response, but excessive heating of normal tissue should be avoided. This makes locoregional heating using phased array systems technically challenging. Online application of hyperthermia treatment planning could help to improve the heating quality. The aim of this study was to evaluate the clinical benefit of online treatment planning during treatment of pelvic tumors heated with the AMC-8 locoregional hyperthermia system. METHODS: For online adaptive hyperthermia treatment planning, a graphical user interface was developed. Electric fields were calculated in a preprocessing step using our in-house-developed finite-difference-based treatment planning system. This allows instant calculation of the temperature distribution for user-selected phase-amplitude settings during treatment and projection onto the patient's computed tomographic scan for online visualization. Online treatment planning was used for 14 treatment sessions in 8 patients to reduce the patients' reports of hot spots while maintaining the same level of tumor heating. The predicted decrease in hot spot temperature should be at least 0.5°C, and the tumor temperature should decrease less than 0.2°C. These predictions were compared with clinical data: patient feedback about the hot spot and temperature measurements in the tumor region. RESULTS: In total, 17 hot spot reports occurred during the 14 sessions, and the alternative settings predicted the hot spot temperature to decrease by at least 0.5°C, which was confirmed by the disappearance of all 17 hot spot reports. At the same time, the average tumor temperature was predicted to change on average -0.01°C (range, -0.19°C to 0.34°C). The measured tumor temperature change was on average only -0.02°C (range, -0.26°C to 0.31°C). In only 2 cases the temperature decrease was slightly larger than 0.2°C, but at most it was 0.26°C. CONCLUSIONS: Online application of hyperthermia treatment planning is reliable and very useful to reduce hot spots without affecting tumor temperatures.
Subject(s)
Hot Temperature , Hyperthermia, Induced/methods , Melanoma/therapy , Pelvic Neoplasms/therapy , Radiotherapy Planning, Computer-Assisted/methods , Therapy, Computer-Assisted/methods , Urinary Bladder Neoplasms/therapy , Uterine Cervical Neoplasms/therapy , Female , Humans , Hyperthermia, Induced/adverse effects , Hyperthermia, Induced/instrumentation , Melanoma/diagnostic imaging , Melanoma/drug therapy , Melanoma/radiotherapy , Pelvic Neoplasms/diagnostic imaging , Pelvic Neoplasms/drug therapy , Pelvic Neoplasms/radiotherapy , Urinary Bladder Neoplasms/diagnostic imaging , Urinary Bladder Neoplasms/drug therapy , Urinary Bladder Neoplasms/radiotherapy , Uterine Cervical Neoplasms/diagnostic imaging , Uterine Cervical Neoplasms/drug therapy , Uterine Cervical Neoplasms/radiotherapyABSTRACT
PURPOSE: To investigate the relationship of thermal skin damage (TSD) to time-temperature isoeffect levels for patients with breast cancer recurrence treated with reirradiation plus hyperthermia (reRT + HT), and to investigate whether the treatment history of previous treatments (scar tissue) is a risk factor for TSD. METHODS AND MATERIALS: In this observational study, temperature characteristics of hyperthermia sessions were analyzed in 262 patients with recurrent breast cancer treated in the AMC between 2010 and 2014 with reirradiation and weekly hyperthermia for 1 hour. Skin temperature was measured using a median of 42 (range, 29-82) measurement points per hyperthermia session. RESULTS: Sixty-eight patients (26%) developed 79 sites of TSD, after the first (n=26), second (n=17), third (n=27), and fourth (n=9) hyperthermia session. Seventy percent of TSD occurred on or near scar tissue. Scar tissue reached higher temperatures than other skin tissue (0.4°C, P<.001). A total of 102 measurement points corresponded to actual TSD sites in 35 of 79 sessions in which TSD developed. Thermal skin damage sites had much higher maximum temperatures than non-TSD sites (2.8°C, P<.001). Generalized linear mixed models showed that the probability of TSD is related to temperature and thermal dose values (P<.001) and that scar tissue is more at risk (odds ratio 0.4, P<.001). Limiting the maximum temperature of a measurement point to 43.7°C would mean that the probability of observing TSD was at most 5%. CONCLUSION: Thermal skin damage during reRT + HT for recurrent breast cancer was related to higher local temperatures and time-temperature isoeffect levels. Scar tissue reached higher temperatures than other skin tissue, and TSD occurred at lower temperatures and thermal dose values in scar tissue compared with other skin tissue. Indeed, TSD developed often on and around scar tissue from previous surgical procedures.
