Between 2007 and 2011, 88 men without clinically palpable disease underwent eMRI for detectable prostate-specific antigen (PSA) after RP. The median interval between RP and eMRI was 32 months (interquartile range, 14-57 months), and the median PSA level was 0.30 ng/mL (interquartile range, 0.19-0.72 ng/mL). Magnetic resonance imaging scans consisting of T2-weighted, diffusion-weighted, and dynamic contrast-enhanced imaging were evaluated for features consistent with local recurrence. The prostate bed was scored from 0-4, whereby 0 was definitely normal, 1 probably normal, 2 indeterminate, 3 probably abnormal, and 4 definitely abnormal. Local recurrence was defined as having a score of 3-4.
Local recurrence was identified in 21 men (24 % ). Abnormalities were best appreciated on T2-weighted axial images (90 % ) as focal hypointense lesions. Recurrence locations were perianastomotic (67 % ) or retrovesical (33 % ). The only risk factor associated with local recurrence was PSA; recurrence was seen in 37 % of men with PSA >0.3 ng/mL vs 13 % if PSA ¡Ü0.3 ng/mL (P<.01). The median volume of recurrence was 0.26 cm3 and was directly associated with PSA (r=0.5, P=.02). The correlation between MRI-based tumor volume and PSA was even stronger in men with positive margins (r=0.8, P<.01).
Endorectal MRI can define areas of local recurrence after RP in a minority of men without clinical evidence of disease, with yield related to PSA. Further study is necessary to determine whether eMRI can improve patient selection and success of salvage RT.