The multicenter, real-world trial showed that men with low-risk or favorable intermediate-risk disease who had higher Prostate Imaging Reporting and Data System (PI-RADS) scores at baseline were more likely to be reclassified with more aggressive disease on a future biopsy, wrote lead author Kiran R. Nandalur, MD and colleagues. The study was published in The Journal of Urology.
This means that without MRI, some cases of prostate cancer are being labeled as lower-risk than they actually are.
The investigators noted that MRI is increasingly being used to choose patients who are appropriate for active surveillance instead of treatment, but related clinical data are scarce.
Although PI-RADS is the preferred metric for characterizing prostate tumors via MRI, “most previous studies on the prognostic implications of baseline PI-RADS score included smaller populations from academic centers, limited inclusion of clinical and pathologic data into models, and/or [are] ambiguous on the implications of PI-RADS score,” they wrote.
These knowledge gaps prompted the present study.
How Were Baseline MRI Findings Related to Prostate Cancer Disease Risk?
The dataset included 1491 men with prostate cancer that was diagnosed at 46 hospital-based, academic, or private practice urology groups. All had low-risk or favorable intermediate-risk disease and had undergone MRI within 6 months before or after initial biopsy, along with enrollment in active surveillance.
“A novel aspect of this study was that the MRIs were not read by dedicated prostate MRI experts at academic institutions, but rather a mix of community and academic radiologists,” Dr. Nandalur, medical director of Corewell Health East Radiology, Royal Oak, Michigan, said in an interview.
After traditional risk factors were accounted for, baseline PI-RADS (four or more lesions) was significantly associated with increased likelihood of biopsy reclassification to high-grade prostate cancer on surveillance biopsy (hazard ratio, 2.3; 95% CI 1.6-3.2; P < .001).
“These patients with suspicious lesions on their initial MRI were more than twice as likely to have higher-grade disease within 5 years,” Nandalur noted. “This result was not only seen in the low-risk group but also in the favorable intermediate-risk group, which hasn’t been shown before.”
Grade group 2 vs 1 and increasing age were also associated with significantly increased risk for reclassification to a more aggressive cancer type.
How Might These Findings Improve Outcomes in Patients With Prostate Cancer?
Currently, 60%-70% of patients with low-risk disease choose active surveillance over immediate treatment, whereas 20% with favorable intermediate-risk disease choose active surveillance, according to Dr. Nandalur.
For low-risk patients, PI-RADS score is unlikely to change this decision, although surveillance intervals could be adjusted in accordance with risk. More notably, those with favorable intermediate-risk disease may benefit from considering PI-RADS score when choosing between active surveillance and immediate treatment.
“Most of the management strategies for prostate cancer are based on just your lab values and your pathology,” Dr. Nandalur said, “but this study shows that maybe we should start taking MRI into account — into the general paradigm of management of prostate cancer.”
Ideally, he added, prospective studies will confirm these findings, although such studies can be challenging to perform and similar data have historically been sufficient to reshape clinical practice.
“We are hoping that [baseline PI-RADS score] will be adopted into the NCCN [National Comprehensive Cancer Network] guidelines,” Dr. Nandalur said.