(68)Ga-PSMA PET/CT for restaging recurrent prostate cancer: which factors are associated with PET/CT detection rate?

Eur J Nucl Med Mol Imaging. 2015 Jul;42(8):1284-94. doi: 10.1007/s00259-015-3078-6. Epub 2015 May 15.

Abstract

Purpose: To assess the association between PSA levels, PSA kinetics and other factors and a pathological (68)Ga-PSMA PET/CT scan in patients with recurrent prostate cancer (rPCa) with biochemical relapse (BR) after radical therapy.

Methods: Seventy consecutive rPCA patients referred for (68)Ga-PSMA PET/CT, matching all the following criteria, were retrospectively evaluated: (a) previous radical prostatectomy or primary radiotherapy with curative intent; (b) BR or persisting high PSA levels after primary treatment; and (c) complete clinical and imaging information. The mean ± SD PSA level was 3.5 ± 5.3 ng/mL (median 1.7, range 0.2 - 32.2 ng/mL), the mean ± SD PSA doubling time (PSAdt) was 6.5 ± 5.5 months (median 5.5, range 1.3 - 31.6 months), and the mean ± SD PSA velocity was 7.9 ± 20.5 (median 2.1, range 0.2 - 147.5 ng/mL/year). Statistical analysis was performed to assess which factors were associated with the detection of rPCa on (68)Ga-PSMA PET/CT.

Results: (68)Ga-PSMA PET/CT was positive in 52 of 70 patients (74.2%). In 30 patients (42.8%) lesions limited to the pelvis were detected. Distant lesions were observed in 8 of patients (11.4%). Local plus systemic lesions were detected in 14 patients (20%). PSA level (p = 0.017) and PSAdt (p = 0.0001) were significantly different between PET-positive patients (higher PSA level, shorter PSAdt) and PET-negative patients (lower PSA, longer PSAdt). ROC analysis showed that PSAdt 6.5 months and PSA 0.83 ng/mL were optimal cut-off values. In multivariate analysis PSAdt was associated with (68)Ga-PSMA PET/CT positivity. (68)Ga-PSMA PET/CT was positive in 17 of 20 patients (85%) with PSA <2 ng/mL and PSAdt <6.5 months, and in 3 of 16 patients (18.7%) with PSA <2 ng/mL and PSAdt ≥6.5 months.

Conclusion: The great potential of (68)Ga-PSMA PET/CT in patients with rPCa and BR was confirmed. PSA and PSAdt were valuable predictors of pathological (68)Ga-PSMA PET/CT findings.

Publication types

  • Evaluation Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Edetic Acid / analogs & derivatives*
  • Gallium Isotopes
  • Gallium Radioisotopes
  • Humans
  • Male
  • Middle Aged
  • Multimodal Imaging
  • Neoplasm Recurrence, Local / diagnostic imaging*
  • Neoplasm Recurrence, Local / pathology
  • Neoplasm Staging
  • Oligopeptides*
  • Positron-Emission Tomography*
  • Prostatic Neoplasms / diagnostic imaging*
  • Prostatic Neoplasms / pathology
  • Radiopharmaceuticals*
  • Sensitivity and Specificity
  • Tomography, X-Ray Computed*

Substances

  • Gallium Isotopes
  • Gallium Radioisotopes
  • Oligopeptides
  • Radiopharmaceuticals
  • gallium 68 PSMA-11
  • Edetic Acid