Validation and applicability of para-aortic lymph nodal contouring atlas in cervical cancer.

Background And Purpose: CTV delineation guidelines for the para-aortic nodal region for patients with cervical cancer have been proposed (Keenan et al., 2018). The purpose of this study was to validate these guidelines with the use of CT datasets of cervical cancer patients with macroscopic PALN treated with definitive (chemo)radiation (CTRT) at our center.

Materials And Methods: Planning CT datasets of 71 cervical cancer patients with gross PA nodal disease treated with EFRT were used. Two hundred and two PALN were identified based on size and morphology on diagnostic CECT, PET CT, or histologically proven PALN. LN regions were divided into upper, middle, and lower and based on their relation to the aorta and IVC. Macroscopic PALN were contoured, and the CTV for PALN irradiation was generated based on the proposed guidelines on ECLIPSE (Version 13.5). The centre of mass (COM) was calculated for each gross PALN. The evaluation was done to review the presence of COM in relation to the CTV PALN.

Results: The most common location of PALN was Left para-aortic (105 LN-52%), Aortocaval (55 LN-27.2%), and Precaval (14 LN-6.9%). Lower PALN were the commonest (104 LN-51.5%). Ninety-three were middle PALN (46%), and 5 were upper PALN (2.5%). After excluding upper PALN, COM for 11 PALN (5.5%) were outside the CTV while 20 were junctional.

Conclusion: Our study shows that more than 95% of PALN in this patient cohort were covered using these guidelines with the addition of an extra 5 mm margin laterally on the left.