Evaluation of tumor recurrences after radical prostatectomy using 18F-Choline PET/CT and 3T multiparametric MRI without endorectal coil: a single center experience

BACKGROUND

To evaluate and compare the utility of 18F-fluorocholine (18F-CH) PET/CT versus 3-Tesla multiparametric MRI (mpMRI) without endorectal coil to detect tumor recurrences in patients with biochemical relapse following radical prostatectomy (RP). Secondarily, to identify possible prognostic variables associated with mpMRI and 18F-CH PET/CT findings.

METHODS

Retrospective study of 38 patients who developed biochemical recurrence after RP between the years 2011 and 2015 at our institution. PET/CT and mpMRI were both performed within 30 days of each other in all patients. The PET/CT was reviewed by a nuclear medicine specialist while the mpMRI was assessed by a radiologist, both of whom were blinded to outcomes.

RESULTS

The median prostate-specific antigen (PSA) value pre-MRI/PET-CT was 0.9 ng/mL (interquartile range 0.4-2.2 ng/mL). There were no differences in the detection rate between 18F-CH PET/CT and mpMRI for local recurrence (LR), lymph node recurrence (LNR) and bone metastases (BM). Separately, mpMRI and 18F-CH PET/CT were positive for recurrence in 55.2% and 52.6% of cases, respectively, and in 65.7% of cases when findings from both modalities were considered together. The detection of LR was better with combined mpMRI and choline PET/CT versus choline PET/CT alone (34.2% vs 18.4%, p = 0.04). Salvage treatment was modified in 22 patients (57.8%) based on the imaging findings. PSA values on the day of biochemical failure were significantly associated with mpMRI positivity (adjusted odds ratio (OR): 30.9; 95% confidence interval (CI): 1.5-635.8). Gleason score > 7 was significantly associated with PET/CT positivity (OR: 13.9; 95% CI: 1.5-125.6). A significant association was found between PSA doubling time (PSADT) (OR: 1.3; 95% CI: 1.0-1.7), T stage (OR: 21.1; 95% CI: 1.6-272.1), and LR.

CONCLUSIONS

Multiparametric MRI and 18F-CH PET/CT yield similar detection rates for LR, LNR and pelvic BM. The combination of both imaging techniques provides a better LR detection versus choline PET/CT alone. The initially planned salvage treatment was modified in 57.8% of patients due to imaging findings. In addition to PSA values, Gleason score, T stage, and PSADT may provide valuable data to identify those patients that are most likely to benefit from undergoing both imaging procedures.

Tumor staging using 3.0 T multiparametric MRI in prostate cancer: impact on treatment decisions for radical radiotherapy

To assess and validate the incorporation of the multiparametric magnetic resonance imaging (mpMRI) tumour category (mT-category) to the conventional clinical tumour category (cT-category), in order to guide the radiotherapy (RT) treatment decisions in prostate cancer. In addition, to identify the clinical factors associated to the technique reliability. mpMRI was performed in 274 prostate cancer patients in order to refine the treatment decisions according to PSA, Gleason Score (GS) and cT-category. Comparisons between the cT and mT-category were performed, as well as the impact on the RT treatment [target volume, doses and hormonal therapy (HT)] independently if it was finally performed. Changes in HT indication for intermediate risk were also analyzed. mpMRI validation was performed with pathological staging (n = 90 patients finally decided to join surgery). The mpMRI upstaging range was 86-94 % for any PSA value or GS. Following mpMRI, 32.8 % of the patients (90/274) were assigned to a different risk group. Compared to cT-category, mpMRI identified more intermediate-risk (46.4 vs. 59.5 %) and high-risk (19.0 vs. 28.8 %) prostate cancer patients. This resulted in a higher indication (p < 0.05) of seminal vesicle irradiation (63.5 vs. 70.0 %), inclusion of any extracapsular disease (T3-T4) within the target volume (1.8 vs. 18.2 %), higher doses (65.3 vs. 88.3 %) and HT associated to RT (45.6 vs. 62.4 %). Global accuracy for mpMRI was higher compared to DRE/TRUS (8.9 vs. 71.1 %, p < 0.05). mpMRI reliability was independent of PSA or GS. mpMRI tumor staging significantly modified the RT treatment decisions in all prostate cancer risk groups.