Interindividual variability of lymph drainages in patients with cervical cancer. Implication on irradiation planning

Lymph node metastases and the number of positive lymph nodes are important prognostic factors for patients with cervical cancer. The most important route is the lateral drainage via the obturator to the internal and external iliac and common iliac area. The risk for common iliac lymph node metastases is increased in patients with positive pelvic or paraaortic lymph nodes. Positive common iliac lymph nodes are associated with a poorer prognosis than positive pelvic lymph nodes excluding common iliac group. For radiation planning in patients with cervical cancer, lymph node regions at high risk for metastases have to be encompassed. Usually, standard fields are used with the upper field border on the fourth/fifth lumbar vertebra. The authors evaluated whether standard fields are sufficient for encompassing the common iliac lymph nodes.

Pretreatment computed tomographic (CT) images of 42 patients with cervical cancer were evaluated to locate the aortic bifurcation and the subsequent common iliac lymph drainage. Anatomy of the lymph drain was correlated with standard radiation portals.

In 17/42 patients (40%) the aortic bifurcation lay superior to the upper field border. In an additional nine patients (21%) the bifurcation was located on the level of the upper field border. In 26/42 patients (62%) standard radiation fields encompassed the common iliac lymph nodes insufficiently.

Common iliac lymph node metastases are found in up to 50% of patients with node-positive cervical cancer. The results of this study demonstrate an unsatisfactory coverage of the common iliac lymph drain by standard fields in most patients. Thus it is necessary to individualize the planning target volume and to include the whole common iliac vessels according to the patient's anatomy on radiation treatment planning CT in order to improve local control.