Comparison of high and low dose rate remote afterloading for cervix cancer and the importance of fractionation.
Analysis of the data obtained from a survey of 56 institutions treating a total of over 17,000 cervix cancer patients with high dose rate (HDR) remote afterloading, shows that the average fractionation regimen is about 5 fractions of 7.5 Gy each to Point A, regardless of stage of disease. Comparison with historical controls treated by the same clinicians at low dose rate (LDR), showed that 5-year survival was statistically significantly better for HDR versus LDR for Stage III patients (47.2% compared to 42.6%, P = 0.005) and for all patients pooled together (60.8% vs. 59.0% P = 0.045). Morbidity rates were considerably lower for HDR versus LDR for both severe (2.23% vs. 5.34%, P less than 0.001) and moderate plus severe complications (9.05% vs. 20.66%, P less than 0.001). There is an apparent geometrical advantage of HDR intracavitary therapy in that there is a reduction in the "hot-spot" rectal and bladder doses relative to Point A of, on average, (13 +/- 4)% for the HDR compared to the LDR treatments. Fractionation of the HDR treatments significantly influenced toxicity: morbidity rates were highly significantly lower for Point A doses/fraction less than or equal to 7 Gy compared with greater than 7 Gy for both severe injuries (1.28% vs. 3.44%, P less than 0.001) and moderate plus severe (7.58% vs. 10.51%, P less than 0.001). The effect of dose/fraction on cure rates was equivocal. Finally, the data showed that for conversion from LDR to HDR the total dose to Point A was reduced on average by a factor 0.54 +/- 0.06.
Gershenson Radiation Oncology Center, Harper Hospital, Detroit, MI 48201.
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Orton
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Seyedsadr
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Somnay
D001918:Brachytherapy / Q000009:adverse effects; D005260:Female; D006306:Health Surveys; D006801:Humans; D009367:Neoplasm Staging; D011832:Radiation Injuries / Q000453:epidemiology / Q000209:etiology; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000009:adverse effects; D016019:Survival Analysis; D002583:Uterine Cervical Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*