Dose-volume analysis and the prevention of radiation sequelae in cervical cancer

We report a 9 year (1975-1983) experience of treatment of carcinoma of the uterine cervix by radiation alone. Computerized dosimetry conforming to the ICRU 38 recommendations was performed for all 348 patients analyzed. Late sequelae were graded as mild (grade 1), moderate (grade 2) and severe (grade 3). The overall rates were grade 3: 9.8%, grade 2: 18%, and grade 1: 19.5%. Of the moderate to severe sequelae, 48% were rectal, 15% rectosigmoid and 21% urinary. The complication rate was highly dependent on the type of intracavitary applicator: lowest for patients treated by two insertions of a standard Fletcher-Suit applicator (grade 3: 5.4%, grade 2: 14.4%) and highest for those receiving uterine stem plus vaginal line sources (grade 3: 29.5%, grade 2: 26%). For 183 patients treated with stem and standard ovoids, moderate and severe rectal and bladder sequelae were analyzed according to critical organ reference doses and reference treatment volumes as defined by ICRU 38, with the addition of a mean rectal dose. Zones of low, moderate and high risk could be defined on dose-volume plots using these parameters. Modification of treatment plans at the Cancer Institute G. F. Leclerc (CGFL) of Dijon according to these concepts produced a reduction in moderate and severe sequelae (grade 3: 14.4-3.4%) without a concurrent increase in pelvic failures. Although the zones of risk proposed can be used directly only with standard Fletcher-Suit applicators and comparable computer dosimetry, the concept can be applied to other systems.