Researchers Move Toward Standardizing Local Prostate Cancer Staging

For patients diagnosed with prostate cancer, staging — which can derive from imaging assessments and/or gross pathologic assessments — has proven key to ensuring optimal counseling and treatment planning.

“Imaging observations used in risk stratification for staging can inform patients and treating physicians of the chances of success among therapeutic options,” said Steven C. Eberhardt, MD, in a recent Radiology editorial, “Local Staging of Prostate Cancer with MRI: A Need for Standardization.” Dr. Eberhardt is a radiologist at the University of New Mexico Health Science Center.

A key feature determining prognosis in men with prostate cancer is the presence of local extraprostatic extension (EPE) of cancer cells. Although MRI of the prostate is generally accepted as the best imaging tool prior to treatment, radiologists have not yet adopted an organized schema for collectively using local staging features to create a system of risk stratification for EPE.

A new Radiology study discussed in the editorial moves toward that goal by proposing a standardized system for EPE reporting of prostate MRI that shows potential risk stratification for patients undergoing prostatectomy.

Testing a Standardized mpMRI-Based Staging System

While MRI has been predominantly used for staging patients with prostate cancer, researchers say there is a potential role for multiparametric MRI (mpMRI) in preoperative staging of prostate cancer for depiction of pathologic EPE and seminal vesicle invasion.

“A major limitation of staging prostate cancer is that the MRI is often falsely positive for extraprostatic extension,” said lead author, Sherif Mehralivand, MD, a research fellow with the National Cancer Institute (NCI)/National Institutes of Health (NIH) Molecular Imaging Program. “This, along with the lack of a standardized nomenclature, inspired us to test a new standardized mpMRI-based staging system.”

Study Highlights

• The study looked at established mpMRI-based prostate cancer staging features over a 10-year period, such as curvilinear contact length, capsular bulge and irregularity, obliteration of the rectoprostatic angle, asymmetry of neurovascular bundles, frank breach of the capsule and seminal vesicle invasion
  • These are considered predictors for EPE on final histopathology

Study Results

• Researchers determined that MRI-based EPE features have varying detection rates for EPE amd were able to define an MRI-based EPE grading system using three features: large capsular contact, capsular bulge, and gross EPE, which are organized into four categories (0, absent; 1, capsular bulge or large capsular contact; 2, capsular bulge and large capsular contact; 4, gross EPE).
• By correlating the MRI-based grading system with final pathology, researchers were able to establish the sensitivity of each EPE feature.
  • Researchers also performed multivariable logistic regression and decision curve analyses to compare the MRI grade model and clinical parameters (prostate-specific antigen, Gleason Score) for pathologic EPE prediction.

• Study demonstrates that the three-feature grading system can satisfactorily predict pathologic EPE and, in fact, performed as well as more complex statistical models for predicting EPE.

“Our grading system demonstrates increasing true positive rates for EPE with the severity of the MRI findings,” said author Baris Turkbey, MD, an associate research physician at the NCI/NIH Molecular Imaging Program. “Furthermore, combining MRI features with such clinical information as serum PSA, initial tumor Gleason Score and digital rectal examination findings result in even better diagnostic performance for predicting pathologic EPE.”

The study’s findings have important implications for radiologists and surgeons as well as patients, according to the authors.

“These results can help radiologists use MRI features to convey the risk of EPE to clinicians, thus improving decision- making for patients,” said author Peter Choyke, MD, branch chief of the NCI/NIH Molecular Imaging Program. “Overall, our findings can potentially improve pre-treatment staging and concomitant treatment planning.”

For More Information

Access the Radiology editorial, “Local Staging of Prostate Cancer with MRI: A Need for Standardization,” and the study, “A Grading System for the Assessment of Risk of Extraprostatic Extension of Prostate Cancer at Multiparametric MRI.”

For Additional Reading

Access the Journal of Nuclear Medicine study, “One-Stop-Shop Whole-Body 68Ga-PSMA-11 PET/MRI Compared with Clinical Nomograms for Preoperative T and N Staging of High-Risk Prostate Cancer.”