The Pelvic Rosetta Classification Project: An Interdisciplinary Proposal for a Lymph Node Map of the Pelvis in Prostate Cancer.

The Pelvic Rosetta Classification (PRC) project aimed to develop an interdisciplinary, landmark-based pelvic lymph node map for patients with prostate cancer to improve communication between imaging specialists and urologists.

Methods

After an intense development phase, we conducted 3 evaluation rounds including 19 clinical experts having consensus meetings after each evaluation round. Experts contoured lymph node areas (LNA) for 2 patients with prostate cancer. Contours were assessed qualitatively and quantitatively. The PRC was further validated by assignment of 30 prostate-specific membrane antigen PET/CT-positive lesions to LNAs. The interrater reliability was calculated using Fleiss κ. Based on the final PRC, a complete contour and a 3-dimensional model were created.

Results

Eight pelvic (external iliac, cranial/caudal obturator fossa, dorsal internal iliac, vesico-prostatic pedicle, mesorectal/perirectal, presacral, preprostatic/retropubic) and 4 extrapelvic (common iliac, intercommon, sigmoid, inguinal) LNAs were defined using anatomic landmarks which are consistently recognizable on imaging and intraoperatively. Strong consensus between experts existed for smaller, well-defined LNAs (e.g., preprostatic/retropubic, mesorectal/perirectal LNAs) compared with regions with proportionally large borders (e.g., obturator fossa, vesico-prostatic pedicle LNAs). Overall, moderate agreement (κ = 0.53) was observed during validation. Discrepancies were mostly encountered for lesions adjacent to borders between LNAs. The final contour and 3-dimensional model were approved by all experts.

Conclusion

The PRC project showed fair reproducibility and validity. Further external validation is needed to assess its influence on interdisciplinary communication and treatment outcomes.