Intention-to-Treat Analysis of ⁶⁸Ga-PSMA and ¹¹C-Choline PET/CT Versus CT for Prostate Cancer Recurrence After Surgery

Abstract

Biochemical recurrence (BCR) after prostate cancer surgery is common, even after additional salvage radiotherapy. BCR might be explained by target miss. Improved diagnostic accuracy provided by PET could potentially circumvent this therapeutic gap. Therefore, we evaluated consecutive 68 Ga-prostate-specific membrane antigen (PSMA) PET/CT, 11 C-choline PET/CT, and standard CT imaging in the same patient with regard to TNM-stage migration and accordingly adapted curative radiotherapy options including ablative treatment of oligometastases (n # 5). The cost efficacy of PET-versus CT-based treatment was also calculated. Methods: The prospective register database (064/2013BO1) was retrospectively searched for patients fulfilling the following 3 inclusion criteria: BCR after radical prostatectomy (pT2-pT4 pN0-pN1 cM0, postoperative radiotherapy allowed); 11 C-choline PET/CT, 68 Ga-PSMA PET/CT, and diagnostic CT performed within 24 h; and available clinical data. Ten treatment routines were defined according to current practice. Furthermore, intention-to-treat and treatment-related costs depending on the shift of TNM stage after imaging were analyzed. Eighty-three patients were eligible (median prostate-specific antigen level, 1.9 ng/mL). Results: Both PET examinations led to concordant results in 72% of patients, whereas the concordance of TNM staging between 68 Ga-PSMA PET and diagnostic CT was only 36%. Incorrect staging would lead to "wrong" treatment and therefore to additional costs. A 68 Ga-PSMA PET study would be cost-effective if additional costs do not exceed €3,844 ($4,312) (vs. CT). The number needed to image was 2 (for CT) and 4 (for 11 C-choline PET) to avoid 1 incorrect treatment. In addition, 68 Ga-PSMA PET staging enabled new curative options in half the patients with previous radiotherapy who otherwise receive palliative androgen deprivation therapy. Conclusion: 68 Ga-PSMA PET/CT is cost-effective in all patients with regard to avoidance of incorrect treatment. It enabled new curative options for patients with previous radiotherapy who are usually treated palliatively. Therefore, 68 Ga-PSMA PET/CT staging should become standard for BCR after surgery with or without radiotherapy.

Diagnostic Performance of [18F]Fluorocholine and [68Ga]Ga-PSMA PET/CT in Prostate Cancer: A Comparative Study

“…Despite the differences in the findings of the two modalities, TNM staging and subsequent patient management was not affected in the majority of patients in the current study (86%; Table 3). This contrasts the findings observed by Schwenck et al They reported a 50% change in patients management using [ 68 Ga]Ga-PSMA as opposed to [ 18 F]Fluorocholine for PET/CT in biochemical recurrence stage [37].…”

Pre-test 68Ga-PSMA-ligand PET/CT positivity in early biochemical recurrent prostate cancer after radical prostatectomy—validation of a prediction model

“…In these cases, early detection and localization of recurrent disease is crucial for further disease management [4,5]. Conventional imaging such as computed tomography (CT) or magnetic resonance imaging as well as choline-based PET often fails to localize biochemical recurrence [4,[6][7][8]. Since its first introduction in 2014, 68 Ga-PSMA-11-ligand positron emission tomography/computed tomography (PET/CT) has been adopted rapidly around the world given its high sensitivity and specificity for the detection and localization PC lesions.…”

68Ga-PSMA-PET/CT-directed IGRT/SBRT for oligometastases of recurrent prostate cancer after initial surgery

“…Regarding detection rate of another PET-tracer, 68 Ga-PSMA identified significantly higher number of PET-positive lesions compared to 11 C-choline [14]. Furthermore, 68 Ga-PSMA-PET/CT demonstrated an improved cost efficacy with a number needed to image of 2 compared to 4 with 11 C-choline PET/CT [21]. Improved accuracy of 68 Ga-PSMA was also substantiated by a previously performed meta-analysis [22,23] especially for BCR after RP with PSA-levels below 1.0 ng/mL [24].…”