The patients had imaging prior to radical prostatectomy (RP) with extended pelvic lymphadenectomy (PLND). PET-CT has mixed reports on its role in detecting metastatic CaP to lymph nodes. DWI is a functional imaging technique using tissue diffusion properties and providing structural information to differentiate between benign and malignant tissues. This study sought to prospectively determine the sensitivity, specificity, and positive and negative predictive values (PPV, NPV) for LN status of PET-CT and DWI.
From 2008 to 2009, a total of 36 patients with a calculated risk of metastasis between 10 and 35%, but no pelvic lymph node metastasis on contrast-enhanced CT imaging were enrolled. Patients underwent PET-CT and DWI-MRI prior to surgery. RP included an extended pelvic lymphadenectomy for prospective mapping by anatomic regions. A total of 733 lymph nodes were removed with a median of 20 nodes per patients. They found CaP in the lymph nodes of 17 patients (47%), corresponding to 38 of 733 lymph nodes (5.2%) divided over 32 different regions. They determined that only 47% of all the positive lymph nodes detected would have been found with a limited PLND. PET-CT had a region-based and patient-based sensitivity of 9.4% and 18.8%, respectively. Surprisingly, 12 lymph node regions containing macrometastases were not positive on imaging. DWI had a region-based and patient-based sensitivity of 18.8% and 42.9%, respectively. It identified 7 LN regions falsely as having CaP in the LNs and missed 11 LN regions containing macrometastases.
The investigators conclude that these imaging techniques cannot be recommended to detect occult LN metastasis.
Budiharto T, Joniau S, Lerut E, Van den Bergh L, Mottaghy F, Deroose CM, Oyen R, Ameye F, Bogaerts K, Haustermans K, Van Poppel H
Eur Urol. 2011 Jul;60(1):125-30