Radiation therapy of the pelvic and paraaortic lymph nodes in cervical carcinoma: a prospective three-dimensional analysis of patient positioning and treatment technique

Purpose: Pelvic box fields in prone position are the standard treatment for patients with cervical carcinomas. The issue investigated in this report is whether this technique should also be used when extending the planning target volume to the paraaortic region. Materials and methods: In a prospective study of eight consecutive patients with cervical carcinomas, two patient positions (prone and supine) and three radiation techniques (A, anteroposterior/posteroanterior opposed fields; B, four-field box; and C, three-field technique) were examined concerning the dose to critical organs. The analysis was based on three-dimensional planning, dose-volume histograms and normal tissue complication probabilities (NTCP). Results: Compared to the prone position, the supine position led to improved organ sparing in four of seven organs (liver, both kidneys, spinal canal). In two of seven organs (rectum and bladder) no difference between prone and supine position was observed. The best sparing of small bowel was achieved in prone position. Technique B followed by technique C in the supine position resulted in the best overall sparing of critical organs concerning the volumes receiving the respective TD5/5 doses or more. Mean NTCP values for liver, rectum and bladder were below 1.0%. The highest values of up to 12% were found for both kidneys in prone position with C and for the spinal canal with A in the prone and supine position. Conclusion: According to this analysis, for the treatment of the pelvic and paraaortic lymph node regions together, supine position and technique B (alternatively C) should be preferred despite the advantages of prone position on belly boards for pelvic irradiation alone