When prostate cancer is diagnosed at an early, low-risk stage, many urologists encourage their patients to consider going on Active Surveillance as a way to hold off on treatment. The rationale for doing so, especially for younger patients, is to avoid the risks of treatment side effects (compromised urinary and sexual function) for as long as safely possible. The key is to know when the safe window is closing, yet the maximum number of treatment options are still available.
A new article[i] reports on a study conducted in the Netherlands on the use of MRI to monitor and possibly restratify the risk level of patients with low-risk prostate cancer. The purpose of this important study was to explore whether 3T multiparametric MRI could reveal cancer changes toward more aggressiveness, and thus indicate the need for a biopsy to confirm a higher risk level.
Four Dutch hospitals were already participating in a large active surveillance trial. With that opportunity already in place, a side study was initiated at one of the hospitals where 82 patients were enrolled in the AS study. From 2009 to 2012, 64 consecutive patients diagnosed with prostate cancer were enrolled in the side study, and each underwent 3TmpMRI and a subsequent MRI-guided biopsy into cancer-suspicious regions according to the PI-RADS scoring system (see other articles on PI-RADS on our website). Risk restratification criteria for discontinuing AS were (1) histopathologically proven magnetic resonance imaging suspicion of node/bone metastases and/or (2) a Gleason growth pattern (GGP) 4 and/or 5 and/or cancer multifocality (?3 foci) in MRGB specimens of a CSR on MP-MRI.
At 3 and 12 months of followup, patients again were scanned and rebiopsied according to the same PI-RADS scoring system. The results were as follows:
a) At 3 months, 14% (9/64) patients were risk-restratified on the basis of imaging and MRI-guided biopsy.
b) At 12 months, 10% (3/30) patients were risk-restratified on the basis of imaging and MRI-guided biopsy.
c) With regard to the PI-RADS scoring system, a score of 1 or 2 (no or little evidence of cancer) had a negative predictive value of 84% for detection of prostate cancer. This means if the scoring predicted there was no cancer, it was correct 84% of the time. However, it correctly predicted there was no Gleason grade 4 or 5 cancer in all cases (100% negative predictive value).
d) A PI-RADS score of 4 or higher (predicting higher risk cancer) that score had a sensitivity of 92%, meaning it correctly detected Gleason score of 4 or 5 as proven on MRI-guided biopsy.
The authors concluded that the use of 3TmpMRI and PI-RADS scoring may play a role in identifying increasing aggression of cancer in patients on AS, warranting an MRI-guided biopsy. This implies that early warning of advancing cancer is possible with sophisticated imaging and experienced readers, affording AS patients an appropriate window of decision for definitive treatment. Furthermore, the authors suggest, “If, during further follow-up, a PI-RADS score of 1 or 2 continues to have a negative predictive value for GGP 4 or 5 containing cancers, a PI-RADS standardized reported MP-MRI may be a promising tool for the selection of prostate cancer patients suitable for active surveillance.” In other words, if the cancer does not appear to be progression, the patient may continue on AS.
Hopefully, other researchers will continue this line of investigation so that appropriate patients can successfully continue to defer treatment, should they so choose.
[i] Hoeks CM, Somford DM, van Oort IM, Vergunst H et al. Value of 3-T multiparametric magnetic resonance imaging and magnetic resonance-guided biopsy for early risk restratification in active surveillance of low-risk prostate cancer: a prospective multicenter cohort study. Invest Radiol. 2014 Mar;49(3):165-72.