Biomedical Engineering Reference
In-Depth Information
8
External Electromagnetic
Methods and Devices
8.1 Introduction .............................................................................................................................139
8.2 Impact of the Quality of the Hyperthermia Treatment on Clinical Outcome ..............139
8.3 Requirements of a Modern External Electromagnetic Heating Device .........................140
8.4 Historical Perspective of the Development of External Electromagnetic Devices .......140
Radiofrequency Inductive Heating • Radiofrequency Capacitive Heating • Radiofrequency
Radiating Heating
8.5 Currently Available Systems ..................................................................................................142
Devices for Superficial Hyperthermia • Loco-Regional Hyperthermia Devices
8.6 Summary and Future Directions ......................................................................................... 154
References .............................................................................................................................................155
Gerard C. van Rhoon
Erasmus MC Daniel den
Hoed Cancer Center
8.1 Introduction
that the good results of RT + HT are sustainable in a routine
clinical setting. In addition, two new positive phase III studies
were published. Issels [5] reported in 340 patients with high-
grade soft tissue sarcoma a doubling of the median disease free
survival (16.2 to 31.7 months) when regional hyperthermia
was added to the standard treatment for this disease. Hua et al.
[6] reported a nearly 10% increase of the 5-year progression
free survival (63.1% for RT vs. 72.7% for RT + HT) in their
randomized study of 180 patients with nasopharyngeal can-
cer after adding intracavity hyperthermia to the conventional
radiotherapy-chemotherapy treatment schedule. Remarkably,
most of the positive results in recent trials are achieved without
increased toxicity.
Within the domain of thermal therapy, external electromagnetic
devices are exclusively used to apply hyperthermia (i.e., inducing
temperatures in the range of 40-45°C for durations of 60-90 min-
utes). Heating tissue involves complex technology whereby the
attained tissue temperature is affected by the temperature-depen-
dent physiological response of the tissue. Moreover, thermal goals
for hyperthermia (HT) are complicated as hyperthermia causes a
multitude of different biological effects on tissue, which are both
time and temperature dependent.
Hyperthermia is always implemented as part of a multimodal,
oncological strategy, (i.e., in combination with radiotherapy or
chemotherapy). Despite the technological and biological chal-
lenges, hyperthermia has proven to possess a great potential
to improve outcome of cancer treatment when combined with
radiotherapy or chemotherapy. “The Kadota Fund International
Forum 2004-Clinical Group Consensus” report published
in March 2008 by the
International Journal of Hyperthermia
reflects a recent and authoritative opinion on clinical HT [1].
In this report, 68 clinicians and biologists from all over the
world conclude that HT is an effective complementary treat-
ment to, and a strong sensitizer of, radiotherapy (RT) and many
cytotoxic drugs. It includes a table of 19 randomized trials, all
showing significantly better results in the treatment arm with
HT. Since then, new clinical results have been reported. The
long-term follow-up of the Dutch Deep Hyperthermia study
[2] showed that the improved 3-year survival rate for the RT +
HT arm (i.e., 27−51%) was still present after 12 years follow-up
[3]. Further, Franckena et al. [4] demonstrated in 378 patients
8.2 Impact of the Quality of the
Hyperthermia treatment
on Clinical Outcome
Ample literature is becoming available revealing the close rela-
tion between HT treatment quality and treatment outcome. Over
time a wide variety of dose parameters have been investigated.
In retrospective studies, dose effect relationships were found
for penetration depth [7], coverage by the 25% iso-SAR contour
[8], and thermal dose expressed in various dose parameters
[9, 10, 11]. Demonstrating a thermal-dose effect relationship
in prospective trials is more difficult. Thrall et al. [12] showed
that thermal dose is related to duration of local control in
canine sarcomas treated by RT + HT. Maquire et al. [13] was less
139