Introduction
There is a significant unmet need for non-invasive methods that can accurately identify patients at increased risk for clinically significant prostate cancer (PCa). SelectMDx is a urine-based molecular test that has been clinically validated for the detection of high-grade PCa. The clinical utility of SelectMDx for guiding prostate biopsy decisions has not been previously assessed. In this multicenter, retro-prospective study, we evaluated the effect of the SelectMDx assay on patient management for men being considered for initial prostate biopsy.
Materials and Methods
The study involved 5 U.S. community urology practices which sequentially enrolled 418 patients who received a SelectMDx test between May 2016 and April 2017, while undergoing consideration for a possible initial prostate biopsy decision. For all subjects, medical record review was conducted in April 2018 to collect SelectMDx results and follow-up clinical data. For patients who received a biopsy, histopathology findings including Gleason Score (GS), and the time between receiving the SelectMDx test and the biopsy were documented. All SelectMDx tests were ordered by the treating urologist for patient management (i.e., not as part of a planned or ongoing study), so the results presumably reflect real-world shared decision making. We determined the number of SelectMDx positive vs. SelectMDx negative men who underwent prostate biopsy. For statistical analyses, chi-square was used to assess differences in proportions and Mann-Whitney for continuous variables.
Results
Of the 418 subjects enrolled, 253 (61%) had a negative SelectMDx test result and 165 (39%) were SelectMDx positive. Average age was 67 (median 67, interquartile range 62 to 72), and average serum PSA level 5.8 ng/mL (5.1, 3.8 to 7.1). The biopsy rate for SelectMDx positive men was 60% (99/165), compared to 12% (31/253) for SelectMDx negative men (P<0.001). For subjects who were biopsied, the median time from SelectMDx results report to biopsy was significantly shorter for SelectMDx positives vs. negatives (median 2 vs. 5 months, P=0.001). To increase the probability that SelectMDx test results were incorporated into the biopsy decision, we evaluated biopsy and cancer detection rates for subjects who were biopsied < 3 months after SelectMDx (Table 1). In this subgroup, 71 (43% of total) SelectMDx positives were biopsied and 27 cancers identified: 17 with low/intermediate grade disease (8 GS 3+3, 9 GS 3+4) and 10 with high grade disease (3 GS 4+3 and 7 > GS8). For the 9 (3.6% of total) SelectMDx negative men biopsied within 3 months of test results, 4 cancers (2 GS 6 and 2 GS 3+4) were identified.
Table 1) Biopsy rates and PCa detection for patients biopsied < 3 months after SelectMDx
*GG = ISUP Gleason Grade group
| |
SelectMDx negative |
SelectMDx positive |
| Biopsies (% of total N) |
9 (3.6%) |
71 (43%) |
| PCa positive |
4 |
27 |
| Gleason Sum (GG*) |
|
|
| GS 3+3 (GG 1) |
2 |
8 |
| GS 3+4 (GG 2) |
2 |
9 |
| GS 4+3 (GG 3) |
0 |
3 |
| GS 8 (GG 4) |
0 |
4 |
| GS 9-10 (GG 5) |
0 |
3 |
Conclusions
In this study, SelectMDx had a significant impact on initial prostate biopsy decision-making in a U.S. community urology setting. Biopsy rates in SelectMDx positive men were 5-fold higher than in SelectMDx negatives. In the subset of patients biopsied within 3 months of receiving test results, 27/71 biopsies performed on SelectMDx positive men were cancer positive, including 10 with high grade disease. In SelectMDx negative men, cancers were identified in 4/9 men biopsied within 3 months of testing, and all were low-grade disease. These results reflect the clinical utility of SelectMDx for biopsy decision-making in real world clinical practice.
