Comparison of high and low dose rate remote afterloading for cervix cancer and the importance of fractionation

• Published in: International journal of radiation oncology, biology, physics Vol. 21; no. 6; pp. 1425 - 1434
• Main Authors: Orton, Colin G., Seyedsadr, Mahmoud, Somnay, Archana
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.1991
• Subjects: Brachytherapy - adverse effects; Ca cervix; Female; HDR brachytherapy; Health Surveys; Humans; LDR brachytherapy; Neoplasm Staging; Radiation Injuries - epidemiology; Radiation Injuries - etiology; Radiotherapy Dosage; Radiotherapy, High-Energy - adverse effects; Remote afterloading; Survival Analysis; Uterine Cervical Neoplasms - mortality; Uterine Cervical Neoplasms - pathology; Uterine Cervical Neoplasms - radiotherapy; Ca cervix; LDR brachytherapy; Remote afterloading; HDR brachytherapy
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/0360-3016(91)90316-V

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 < 0.001) and moderate plus severe complications (9.05% vs. 20.66%, P < 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 ≤ 7 Gy compared with > 7 Gy for both severe injuries (1.28% vs. 3.44%, P < 0.001) and moderate plus severe (7.58% vs. 10.51%, P < 0.001). The effect of dose/fraction on cure retes 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.