A First-in-Human Study of 68Ga-Nanocolloid PET/CT Sentinel Lymph Node Imaging in Prostate Cancer Demonstrates Aberrant Lymphatic Drainage Pathways.

Abstract

Our goal was to assess the feasibility, safety, and utility of a novel 68Ga-nanocolloid radiotracer with PET/CT lymphoscintigraphy for identification of sentinel lymph nodes (SLNs). Methods: This was a pilot study of patients from a tertiary cancer hospital who required insertion of gold fiducials for prostate cancer radiation therapy. Participation did not affect cancer management. Ultrasound-guided transperineal intraprostatic injection of a PET tracer (iron oxide nanocolloid labeled with 68Ga) was performed after placement of the fiducials. PET/CT lymphoscintigraphy imaging took place at approximately 45 and 100 min after injection of the tracer. The study was monitored using a Bayesian design with the assumption that at least 1 SLN could be identified in at least two thirds of cases with more than 80% confidence. Results: SLN identification was successful in all 5 participants, allowing completion of the pilot study as per protocol. No adverse effects were observed. Unexpected potential pathways for transit of malignant cells, as well as the expected regional drainage pathways, were discovered. Rapid tracer drainage to pelvic bone, perivesicular, mesorectal, inguinal, and Virchow nodes was identified. Conclusion: SLN identification using 68Ga-nanocolloid PET/CT can be successfully performed. Nontraditional pathways of disease spread were identified, including drainage to pelvic bone and to perivesicular, mesorectal, inguinal, and Virchow nodes. The prevalence of both aberrant and nonlymphatic pathways of spread should be further investigated with this technique.