Anatomic study of the pelvis in carcinoma of the uterine cervix as related to the box technique

Purpose: To review the radiation therapy "box" technique for cancer of the cervix by means of magnetic resonance imaging (MRI), lymphangiography, and anatomic studies on cadavers. Methods and Materials: From 1993 to 1996, the anatomic borders of the "box" technique used at our Radiation Oncology Department-the superior border of the AP-PA fields at the inferior edge of L4; the inferior border at the inferior edge of the ischium; the lateral borders placed 2.5 cm outside of the bony pelvis rim; the anterior border of the lateral fields over the anterior edge of the pubic symphysis; and the posterior at the S2-S3 interspace-were reviewed in 35 sagittal MRI and 10 lymphangiographies of patients with FIGO IB (6), IIA (6), IIB (19), IIIB (3), and IVA (1). An anatomic revision was conducted on 30 cadavers to identify aortic bifurcation, lymphatic nodes, and uterus flexion. Results: In 50% of the patients with PICO IB, the posterior border of the lateral field was inadequate to encompass the planning target volume (PTV), and in 67% with Stage IIA. In IIB, the anterior border was inadequate in 1 patient, and the posterior in 8 (42%). In IIB and IVA patients, the PTV was not encompassed. When correlating the anterior and posterior borders of the lateral field and the treatment volume in the 35 sagittal MRIs, the posterior border of the lateral field was inadequate in 49%, and the anterior border in 9% of the cases. According to the lymphangiography, the portals encompassed the external iliac nodes. Dissected female pelvises revealed that the aortic bifurcation occurred at the level of the inferior L4 edge in 80% of the cadavers. There was no correlation between uterus flexion in MRIs and in cadavers. Conclusion: The design of the lateral fields of the four-field technique for the irradiation of the uterine cervix based on anatomic bone references failed to encompass the planning-target volume in a significant number of patients. (C) 1999 Elsevier Science Inc.