Objective: To compare the accuracy of lymph node staging using pelvic MRI or CT to that of laparoscopic pelvic lymph node dissection (LPLND) in prostate cancer patients prior to radical radiotherapy.
Material and methods: A total of 55 consecutive patients at high risk of locally advanced disease [prostate-specific antigen (PSA) > 10 ng/ml, Gleason score 7 or worse on biopsy, normal (99m) Tc bone scan] underwent either a pelvic MRI (n = 42) or CT (n = 13) scan and subsequent LPLND. Preoperative staging was compared to the histology of the lymph node specimens obtained.
Results: A total of 20/55 (36.4%) patients had pelvic lymph node metastases confirmed by LPLND. MRI identified three patients (27.3%) with pelvic lymph node metastases and missed eight (72.7%) whilst CT identified none of nine patients with pelvic lymph node metastases. The groups with histologically-positive and -negative nodes had similar mean ages (63 vs 65 years; p = 0.52), Gleason scores (6.8 vs 6.5; p = 0.41) and PSA levels (43.1 vs 31.4 ng/ml; p = 0.56).
Conclusion: The presence or absence of lymph node metastases has critical implications for the prognosis and treatment of prostate cancer. In this study both MRI and CT missed many cases of lymph node metastases in "high-risk" patients. While a positive scan seems likely to indicate nodal metastases, the low sensitivity in high-risk patients seems unacceptable if treatment decisions are to be based on accurate staging, and LPLND offers an alternative.