Prospective, Multisite, International Comparison of 18F-Fluoromethylcholine PET/CT, Multiparametric MRI, and 68Ga-HBED-CC PSMA-11 PET/CT in Men with High-Risk Features and Biochemical Failure After Radical Prostatectomy: Clinical Performance and Patient Outcomes

Abstract

A significant proportion of men with rising prostate-specific antigen (PSA) levels after radical prostatectomy (RP) fail prostate fossa (PF) salvage radiation treatment (SRT). This study was done to assess the ability of ¹⁸F-fluoromethylcholine (¹⁸F-FCH) PET/CT (hereafter referred to as ¹⁸F-FCH), ⁶⁸Ga-HBED-CC PSMA-11 PET/CT (hereafter referred to as PSMA), and pelvic multiparametric MRI (hereafter referred to as pelvic MRI) to identify men who will best benefit from SRT. Methods: Prospective, multisite imaging studies were carried out in men who had rising PSA levels after RP, high-risk features, and negative/equivocal conventional imaging results and who were being considered for SRT. ¹⁸F-FCH (91/91), pelvic MRI (88/91), and PSMA (31/91) (Australia) were all performed within 2 wk. Imaging was interpreted by experienced local/central interpreters who were masked with regard to other imaging results, with consensus being reached for discordant interpretations. Expected management was documented before and after imaging, and data about all treatments and PSA levels were collected for 3 y. The treatment response to SRT was defined as a reduction in PSA levels of >50% without androgen deprivation therapy. Results: The median Gleason score, PSA level at imaging, and PSA doubling time were 8, 0.42 (interquartile range, 0.29-0.93) ng/mL, and 5.0 (interquartile range, 3.3-7.6) months. Recurrent prostate cancer was detected in 28% (25/88) by pelvic MRI, 32% (29/91) by ¹⁸F-FCH, and 42% (13/31) by PSMA. This recurrence was found within the PF in 21.5% (19/88), 13% (12/91), and 19% (6/31) and at sites outside the PF (extra-PF) in 8% (7/88), 19% (17/91), and 32% (10/31) by MRI, ¹⁸F-FCH, and PSMA, respectively (P < 0.004). A total of 94% (16/17) of extra-PF sites on ¹⁸F-FCH were within the pelvic MRI field. Intrapelvic extra-PF disease was detected in 90% (9/10) by PSMA and in 31% (5/16) by MRI. ¹⁸F-FCH changed management in 46% (42/91), and MRI changed management in 24% (21/88). PSMA provided additional management changes over ¹⁸F-FCH in 23% (7/31). The treatment response to SRT was higher in men with negative results or disease confined to the PF than in men with extra-PF disease (¹⁸F-FCH 73% [32/44] versus 33% [3/9] [P < 0.02], pelvic MRI 70% [32/46] versus 50% [2/4] [P was not significant], and PSMA 88% [7/8] versus 14% [1/7] [P < 0.005]). Men with negative imaging results (MRI, ¹⁸F-FCH, or PSMA) had high (78%) SRT response rates. Conclusion:¹⁸F-FCH and PSMA had high detection rates for extra-PF disease in men with negative/equivocal conventional imaging results and rising PSA levels after RP. These findings affected management and treatment responses, suggesting an important role for PET in triaging men being considered for curative SRT.

Keywords: 18F-fluoromethylcholine; PET; PSMA; biochemical recurrence; multiparametric MRI; prostate cancer.

FIGURE 1.

Flow chart for determining composite reference standard used in assessment of diagnostic accuracy for PSMA, ¹⁸F-FCH, and pelvic MRI. FN = false negative; FP = false positive; TP = true positive.

FIGURE 2.

Man with a rising PSA (0.29 ng/mL) 5 y after RP. Imaging demonstrates PF recurrence on PSMA (A), MRI (B), and ¹⁸F-FCH (C). Solitary PSMA-avid (D), ¹⁸F-FCH (E) and MRI-negative focus in thoracic spine (red arrow) was confirmed as true-positive (repeat imaging and targeted treatment response).

FIGURE 3.

Treatment response to targeted SRT stratified by imaging result (negative results or fossa-confined disease vs. extra-PF disease) for pelvic MRI, ¹⁸F-FCH, and PSMA. mpMRI = multiparametric MRI.