JU INSIGHT Stability of Prognostic Estimation Using CAPRA Score With Imaging- vs Physical Exam–based Staging

By: Kevin Chang, BA, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Scott A. Greenberg, MD, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Janet E. Cowan, MA, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Robert Parker, MD, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Kevin Shee, MD, PhD, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Samuel L. Washington III, MD, MAS, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Hao G. Nguyen, MD, PhD, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Katsuto Shinohara, MD, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Peter R. Carroll, MD, MPH, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Matthew R. Cooperberg, MD, MPH, UCSF-Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco | Posted on: 30 Aug 2023

Chang K, Greenberg SA, Cowan, JE, et al. Stability of prognostic estimation using the CAPRA score incorporating imaging-based vs physical exam-based staging. J Urol. 2023;210(2):281-289.

Study Need and Importance

The latest edition of the American Joint Committee on Cancer Staging Manual for prostate cancer emphasizes that clinical T stage should still reflect only digital rectal examination (DRE) findings despite recent improvements in imaging, particularly transrectal ultrasound (TRUS) and multiparametric prostate MRI, on which providers increasingly rely to define clinical stage. Tumor staging standards and performance of risk assessment models must be verified periodically to be commensurate with changing standards and practice patterns. We leveraged our prospectively populated clinical Urologic Outcomes Database to assess the impact of incorporating imaging findings into T-staging on predictive performance of the well-validated Cancer of the Prostate Risk Assessment (CAPRA) score.

What We Found

We calculated 2 CAPRA scores—(1) a standard CAPRA reflecting DRE-based T stage and (2) a modified CAPRA reflecting imaging-based T stage—for 2,222 men who underwent radical prostatectomy for prostate cancer staged ≤cT3a on both DRE and imaging (TRUS/MRI). A total of 377 patients (17%) increased in CAPRA score with imaging-based staging. We found that DRE-based and imaging-based CAPRA scores were comparably accurate for predicting biochemical recurrence (see Table) with similar model discrimination and net benefit. Equally impressive were the nearly identical hazard ratios for recurrence in our current CAPRA models compared to the original 2005 publication.

Table. Univariate Cox Proportional Hazards Regression Model Results for Cancer of the Prostate Risk Assessment Score With T Stage Based on Digital Rectal Examination or Imaging for Outcome of Biochemical Recurrence

CAPRA model	Hazard ratio (95% CI)	P value	Time-dependent AUC at 48 mo after surgery
DRE based	1.54 (1.48-1.61)	< .01	0.76
Imaging based	1.52 (1.46-1.58)	< .01	0.77
2005 CAPRA	1.5 (1.4-1.6)
Abbreviations: AUC, area under the curve; CAPRA, Cancer of the Prostate Risk Assessment; CI, confidence interval; DRE, digital rectal examination.

Limitations

Findings from our single-center database may not necessarily apply to other prostate cancer populations where imaging and/or staging is performed or recorded differently. We also grouped TRUS and MRI into a single “imaging” bucket for our analysis where future studies might benefit from stratifying them.

Interpretation for Patient Care

As it stands, there is no need to update the CAPRA score in the modern era to explicitly use clinical staging by DRE or imaging. The performance metrics of each CAPRA score are statistically indistinguishable. Urologists should feel confident in using staging information from whichever method they have readily available for a patient’s CAPRA score calculation.