Biparametric MRI in prostate cancer during active surveillance: is it safe?

Abstract

Active surveillance (AS) is the preferred option for patients presenting with low-intermediate-risk prostate cancer. MRI now plays a crucial role for baseline assessment and ongoing monitoring of AS. The Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) recommendations aid radiological assessment of progression; however, current guidelines do not advise on MRI protocols nor on frequency. Biparametric (bp) imaging without contrast administration offers advantages such as reduced costs and increased throughput, with similar outcomes to multiparametric (mp) MRI shown in the biopsy naïve setting. In AS follow-up, the paradigm shifts from MRI lesion detection to assessment of progression, and patients have the further safety net of continuing clinical surveillance. As such, bpMRI may be appropriate in clinically stable patients on routine AS follow-up pathways; however, there is currently limited published evidence for this approach. It should be noted that mpMRI may be mandated in certain patients and potentially offers additional advantages, including improving image quality, new lesion detection, and staging accuracy. Recently developed AI solutions have enabled higher quality and faster scanning protocols, which may help mitigate against disadvantages of bpMRI. In this article, we explore the current role of MRI in AS and address the need for contrast-enhanced sequences. CLINICAL RELEVANCE STATEMENT: Active surveillance is the preferred plan for patients with lower-risk prostate cancer, and MRI plays a crucial role in patient selection and monitoring; however, current guidelines do not currently recommend how or when to perform MRI in follow-up. KEY POINTS: Noncontrast biparametric MRI has reduced costs and increased throughput and may be appropriate for monitoring stable patients. Multiparametric MRI may be mandated in certain patients, and contrast potentially offers additional advantages. AI solutions enable higher quality, faster scanning protocols, and could mitigate the disadvantages of biparametric imaging.

Keywords: Active surveillance; Biparametric; MRI; Prostate cancer.

Fig. 1

False positive DCE findings on AS follow-up. 74-year-old patient, presenting PSA 10.95 ng/mL. A–C Baseline MRI shows ill-defined T2 change (A) at the left mid-PZ, with a 12 × 9 mm area of marked restricted diffusion (B), with associated focal early enhancement (C), consistent with a PI-RADS 4 lesion (arrows). Targeted biopsy shows Gleason 3 + 4 = 7 (10% Gleason 4) in 3/3 cores. D–F MRI at 12 months, PSA 10.84 ng/mL. Stable conspicuity and size of lesion on T2 (D) and ADC maps (E), but increase in the degree of enhancement to 22 × 12 mm (F, arrows). PRECISE score 3—findings considered a false positive. The patient remains on AS

Fig. 2

Value of DCE in patients with poor quality DWI. 71-year-old patient with a left THR, presenting PSA 6.01 ng/mL. A–C Baseline MRI: 14 × 5 mm PI-RADS 4 lesion in the medial left apex PZ with focal low T2 signal (A), nondiagnostic DWI due to THR (B), and focal early enhancement on DCE (C). Targeted biopsy shows Gleason score 3 + 4 = 7 (approximately 5% pattern 4), in 2/2 cores, 5 mm maximum tumour length. D–F MRI at 36 months with PSA 8.63 ng/mL. Increase in conspicuity on T2 (D), DWI remains nondiagnostic (E), but with a clear increase in the degree of enhancement on DCE to 21 × 7 mm (F, arrows). PRECISE score 4. Repeat biopsy shows Gleason score 3 + 4 = 7 (40% pattern 4), in 2/2 cores, 8 mm max tumour length. The patient treated with external beam radiotherapy

Fig. 3

bpMRI versus mpMRI affecting PI-RADS score. 66-year-old patient, presenting PSA 5.88 ng/mL. A–C Baseline MRI shows ill-defined PI-RADS 3 change on T2 (A), with mild restricted diffusion on ADC (B) and b-value imaging (not shown), PI-RADS 3, with associated marked focal early enhancement, DCE positive (C, arrow). Overall PI-RADS score 3 + 1 = 4; targeted biopsy shows Gleason 3 + 4 = 7 (Pattern 4 = < 5%) extending for a maximum length of 4.2 mm. D, E MRI at 12 months, PSA 5.43 ng/mL. Stable appearances on Ts (D) and ADC maps (E, arrow); however, PI-RADS score 3, reduced from score 4 due to employment of a bpMRI only

Fig. 4

Faster acquisition by applying DLR. A Standard-of-care axial fast-recovery fast-spin-echo T2WI sequence, acquisition time 4:34 minutes. B C T2 acquisition with a reduced number of and retrospectively reconstructed with medium DLR (B) and high DLR (C), with resultant reduction in scan times to 3:05 minutes and 2:19 minutes, respectively, without compromising image quality