Introduction: The 4K score and MRI are used as screening tools to add specificity to PSA. Here we aim to evaluate 4K and its added value when combined with prostate MRI in the detection of high-grade prostate cancer (HG PCa) and avoidance of unnecessary biopsies.
Methods: Patients referred at UCSF between 2016-2019 for PCa screening were enrolled and had 4K score testing with or without MRI. Using logistic regression and AUC we evaluated the performance of the 4K score (with four different cut points: 7.5, 10, 15 and 20), MRI, PSAD and TRUS in detecting HG PCa (defined as Gleason grade (GG) 3+4 or higher). In the subgroup of patients that had an MRI and underwent biopsy, with PSA 2.5-10 ng/mL and negative DRE, we determined the number of avoided unnecessary biopsies (with GG 3+3 cancer or no cancer) and missed HG PCa using 4K at different cut points with or without MRI.
Results: A total of 617 men were enrolled, 443 had an MRI and 332 were biopsied. Mean age was 65.3 years, median PSA was 6.15 ng/ml (IQR 4.75-8.40) and median 4K was 14.0 (IQR 7.00-29.0). Logistic regression showed that having a 4K >7.5 or PI-RADS 4/5 lesion on MRI (P4/5) were both strongly associated with finding HG PCa: 4K OR 12.9 (CI 4.58-36.1), P4/5 OR 6.20 (CI 3.93-9.79), p<0.01; and increasing the 4K cut point made the association stronger. P4/5 on MRI had higher AUC for detecting HG PCa than 4K >7.5 (AUC 0.858 vs 0.780, p<0.01). Combining 4K >7.5 and P4/5 lesion on MRI also increased AUC for detecting HG PCa. In the biopsy subgroup, a normal 4K (=7.5) avoided fewer unnecessary biopsies than negative MRI (15 with MRI resulted in minimal missed HG PCa and more avoided unnecessary biopsies.
Conclusions: Our data suggest that PI-RADS 4/5 on MRI has better discrimination for detecting HG PCa than 4K. MRI however is not sensitive enough to detect all HG PCa cases and 4K testing alone could be sufficient as the initial tool to select patients who may benefit from a biopsy. Using higher 4K cut points such as >15 combined with MRI however allows for more avoided unnecessary biopsies with minimal missed HG PCa cases. Source of