NRG Oncology Updated Consensus Contour Atlas on Pelvic Lymph Node Volumes

Presenting author:
William Hall, MD

By Edina Wang, MD

William Hall, MD, and colleagues presented their update to the 2009 RTOG consensus atlas that has been widely used to assist with contouring pelvic nodal volumes for intact and post-operative prostate cancer cases. Since 2009, data has emerged, including molecular imaging, that has furthered informed nodal recurrence patterns. As a result, a need was identified for an updated NRG Oncology consensus contour atlas.

The authors of NRG Oncology Updated International Consensus Atlas on Pelvic Lymph Node Volumes for Intact and Post-Operative Prostate Cancer first performed a literature review on pelvic nodal recurrence patterns since 2007. These publications were in categories of existing updated nodal consensus atlases, surgical/intact disease lymphatic drainage patterns, post-operative recurrence patterns and molecular PET based recurrence patterns. Following the data presentation from this review, 18 genitourinary radiation oncologists were asked to contour the nodal clinical target volume (CTV) in three different cases that included a post-operative, intact node positive and intact node negative prostate case. Results of the consensus contouring exercise were reviewed by the contouring group in January of 2020.

Contour analysis was performed using Sorensen-Dice similarity coefficient and Hausdorff distance. These metrics were calculated and compared to a baseline contour that was created following the 2009 RTOG nodal contouring atlas. The resulting metrics were discussed at the ASTRO session GU 04-Prostate Dose, Volumes and Outcomes on Monday, October 26. In general, discordance with the 2009 RTOG consensus atlas was seen in this group of radiation oncologists. Four regions of CTV controversy were identified, including the superior most aspect of the common iliac nodes, the transition from the external iliac to the inguinal contours, the inclusion of the peri-prostatic nodes and the inclusion of peri-rectal nodes. Contours of clinically positive nodes also had variations. Areas of contouring controversy were reviewed and discussed with the investigators reaching a consensus on the final borders for each of these areas. Multiple changes to the existing nodal contouring atlas were recommended. These changes include a new superior border, obturator nodal border and a new contour transition point from the external iliacs to the inguinal nodal region.

In summary, the new NRG Oncology consensus nodal contouring atlas as presented in this study makes several changes to the existing RTOG consensus atlas. Consensus contours from this study are presented on both CT and MR. Given the wide range of contour volumes, an example of an expanded volumes including peri-rectal nodes was also included in the new atlas. Variations in contouring strategies are presented for consideration. This study also presents common dose and fractionation schedules and corresponding constraints for consideration.

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NRG Oncology Updated International Consensus Atlas on Pelvic Lymph Node Volumes for Intact and Post-Operative Prostate Cancer was released onDemand on Monday, October 26 in the Science Center, as part of Scientific session (SS) 22.

Published on: October 28, 2020


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