Use of the concept of equivalent biologically effective dose (BED) to quantify the contribution of hyperthermia to local tumor control in radiohyperthermia cervical cancer trials, and comparison with radiochemotherapy results.
OBJECTIVE
To express the magnitude of contribution of hyperthermia to local tumor control in radiohyperthermia (RT/HT) cervical cancer trials, in terms of the radiation-equivalent biologically effective dose (BED) and to explore the potential of the combined modalities in the treatment of this neoplasm.


METHODS
Local control rates of both arms of each study (RT vs. RT+HT) reported from randomized controlled trials (RCT) on concurrent RT/HT for cervical cancer were reviewed. By comparing the two tumor control probabilities (TCPs) from each study, we calculated the HT-related log cell-kill and then expressed it in terms of the number of 2 Gy fraction equivalents, for a range of tumor volumes and radiosensitivities. We have compared the contribution of each modality and made some exploratory calculations on the TCPs that might be expected from a combined trimodality treatment (RT+CT+HT).


RESULTS
The HT-equivalent number of 2-Gy fractions ranges from 0.6 to 4.8 depending on radiosensitivity. Opportunities for clinically detectable improvement by the addition of HT are only available in tumors with an alpha value in the approximate range of 0.22-0.28 Gy(-1). A combined treatment (RT+CT+HT) is not expected to improve prognosis in radioresistant tumors.


CONCLUSIONS
The most significant improvements in TCP, which may result from the combination of RT/CT/HT for locally advanced cervical carcinomas, are likely to be limited only to those patients with tumors of relatively low-intermediate radiosensitivity.
Plataniotis
George A
GA
Department of Oncology, Aberdeen Royal Infirmary, Aberdeen, UK. george.plataniotis@nhs.net
Dale
Roger G
RG
D000465:Algorithms; D016923:Cell Death; D049109:Cell Proliferation; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods; D016014:Linear Models; D011836:Radiation Tolerance / Q000502:physiology; D016032:Randomized Controlled Trials as Topic; D012062:Relative Biological Effectiveness; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*