SUO 2017: The Need of CT Imaging for Staging High Risk Prostate Cancer

Washington, DC ( Dr. Reichard discussed the need/utility of CT imaging for staging high risk prostate cancer patients already staged with technetium-99m bone scan and pelvic MRI. Indeed, the use of pelvic MRI for staging and/or surgical planning is increasing, especially in NCCN high risk and very high-risk prostate cancer patients. However, most of these patients also undergo CT and bone scan imaging for metastatic staging work up, often prior to tertiary center referral. The authors hypothesized that the omission of a CT scan in the metastatic work up of high-risk prostate cancer patients undergoing pelvic MRI and bone scan would not cause information loss regarding metastatic status and would reduce the burden of unwanted incidental findings. As such, the objective of this study was to analyze the incidence of pelvic and distant metastases identified on CT scan compared with that of pelvic MRI and bone scan.

The authors identified 271 high-risk prostate cancer patients at MD Anderson Cancer Center between 2006 and 2016. Among these patients, 160 had a CT scan, pelvic MRI and bone scan available for review. Both pelvic MRI and CT scan images were re-reviewed by a single radiologist. ANOVA was used to test means among groups and chi-square analysis was used for categorical variables. The clinical characteristics of patients with bone scan only, CT only, or no imaging did not differ from those with all three imaging modalities (all p>0.05). The overall incidence of lymphadenopathy on imaging was generally low (3.1% for CT scan and 5% for pelvic MRI). Only one patient had distant lymphadenopathy on CT which was biopsy negative. No patients with pelvic lymphadenopathy on pelvic MRI had distant lymphadenopathy on CT imaging. Moreover, 50% of the patients with pelvic lymphadenopathy on CT imaging had negative biopsies. Pelvic MRI specific findings included 18% of patients with seminal vesicle involvement, 26% with neurovascular bundle involvement, and 36% with extraprostatic extension. Importantly, 11.9% of CT scans had incidental findings, of which 84% were of minimal clinical significance. 

In conclusion, Dr. Reichard highlighted that in this cohort of high and very high-risk prostate cancer patients, the rate of incidental findings on CT imaging is consistent with reported literature, with the majority being of no clinical significance. Additionally, for most patients with pelvic MRI and bone scan, CT imaging did not add any additional informative data regarding extra-pelvic disease status. These findings are important and should be used as a guide for additional cost-effectiveness analyses.

Presented by: Chad Reichard, MD Anderson Cancer Center, Houston, TX

Co-authors: Tharakeswara Bathala, MD, MBBS, Justin Gregg, Janet Kukreja, MD, Mary Achim, John Davis, MD, Brian Chapin, MD

Written by: Zachary Klaassen, MD, Society of Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre @zklaassen_md at the 18th Annual Meeting of the Society of Urologic Oncology, November 20-December 1, 2017 – Washington, DC

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