Limitations of Multiparametric Magnetic Resonance Imaging for Detection of Extraprostatic Extension in Prostate Cancer: Implications for Nerve Sparing Approaches
Stephen Schmit, BS1, Rebecca Ortiz, BA2, Randall Li, MD1, Siddharth Marthi, BA1, Ji Whae Choi, BA1, Kathleen Wu, BA1, Philip Caffery, PhD2, Christopher Tucci, MS1, Mohammad Hout, MD1, David W. Sobel, MD1, Dragan Golijanin, MD1, Gyan Pareek, MD1, Elias Hyams, MD1.
1Minimally Invasive Urology Institute, The Miriam Hospital; The Warren Alpert Medical School of Brown University, Providence, RI, USA, 2Minimally Invasive Urology Institute, The Miriam Hospital, Providence, RI, USA.
BACKGROUND: Multiparametric magnetic resonance imaging (MRI) is increasingly used for pre-operative staging of prostate cancer as well as for surgical planning. Concern for extraprostatic extension (EPE) on MRI suggests that wider dissection (inter-, extra-fascial, or non-nerve sparing approaches) may be warranted. It is not clear how MRI findings and Grade Group (GG) interact to determine the presence of EPE on surgical pathology.
METHODS: A retrospective review of a robotic assisted laparoscopic radical prostatectomy (RALP) database from a single academic institution from 2016-2020 was performed. MRI reports were assessed for positive or possible EPE findings to determine the sensitivity and negative predictive value (NPV) for pathological EPE. The data was further stratified by GG to determine the relationship between tumor grade and MRI findings.
RESULTS: A total of 173 patients underwent at least one MRI prior to RALP. 106/173 (61%) patients had GG 3-5 tumors, 59/173 (34%) had GG 4-5 tumors, and 45/173 (26%) had GG 5 tumors. The overall sensitivity of MRI for pathological EPE was 37.6%, and stratification by GG yielded the following sensitivities: GG 3-5, 40.6%; GG4-5, 50.8%; GG 5, 53.3%. The overall NPV was 50.2%, and stratification revealed the following NPVs: GG 3-5, 31.6% ; GG 4-5, 16.2%; GG 5, 12%.
CONCLUSIONS: The sensitivity of MRI for EPE improved with higher grade prostate tumors, but remained relatively low even with GG 5 tumors. NPV for EPE was low and decreased further with higher grade tumors. This suggests caution in aggressive nerve sparing approaches with higher grade tumors even in the setting of a reassuring MRI.
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