RADIOLOGY Corner PSMA PET CT to Assess Prostate Cancer Recurrence after Radiation or Surgery
By: Elliot Anderson, MBBS, BMedSc; Patrick Bowden, MBBS, FRANZCR; Jeremy Grummet, MBBS, MS, FRACS | Posted on: 29 Jan 2021
A 66-year-old man was referred for elevated prostate specific antigen (PSA; 5.6 ng/ml) and underwent transperineal (TP) prostate biopsy that found low volume Gleason score 3+3=6 (ISUP Grade Group 1) prostate cancer (PCa). After a 15-month period of active surveillance the patient's PSA rose to 8.2 ng/ml and a multiparametric prostate magnetic resonance imaging (MRI) discovered 2 PI-RADS™ 5 lesions. The patient was rebiopsied using cognitive fusion, revealing extensive Gleason score 4+3=7 (ISUP Grade Group 3) PCa. He underwent a robotic assisted prostatectomy (without pelvic lymph node dissection) with histopathology demonstrating pT2c Gleason score 4+3=7 (ISUP Grade Group 3) and clear margins. PSA was undetectable at 3 months, then rose to 0.11 at 12 months, and 0.58 ng/ml at 18 months postoperatively.
The patient underwent a whole body gallium-68 prostate specific membrane antigen (PSMA) positron emission tomography/computerized tomography (PET-CT), which showed no evidence of PSMA avid PCa. The patient proceeded to prostate bed salvage radiotherapy (70Gy in 35 fractions) alone (no hormone therapy), which he tolerated with minimal toxicity. After treatment his PSA dropped to 0.08 ng/ml and 0.01 ng/ml at 1 and 2 years postradiation, respectively. Three and a half years after prostate bed salvage radiotherapy his PSA increased sharply to 0.79 ng/ml (PSA doubling time (PSAdt) 2.4 months) prompting a repeat whole body gallium-68 PSMA PET-CT. This time it was positive, demonstrating metastatic disease in a lymph node in the right internal iliac station (see figure). This metastatic deposit was treated with stereotactic radiotherapy (50Gy in 10 fractions) alone (no hormone therapy). At 4 months after treatment the patient has had no radiation toxicity and his PSA has dropped to 0.01 ng/ml.
Early identification of recurrent disease is of critical importance for managing PCa after curative intent therapy. Visualization of metastases via PSMA PET-CT allows for metastasis directed therapies (MDT) such as stereotactic radiation treatment. PSMA PET-CT has demonstrated excellent results as an accurate diagnostic modality following biochemical recurrence. Importantly, PSA level and kinetics impact recurrence detection rate. Our case study patient underwent 2 PSMA PET scans 3.5 years apart, following a PSA rise with rapid PSAdt. In a study by Ceci et al a positive scan was demonstrated in 85% of patients with PSA less than 2 ng/ml and PSAdt less than 6.5 months. 1 This is congruent with a retrospective study by Eiber et al that found pathological scans in 72.7% of men with PSA values between 0.5 to less than 1 ng/ml after radical prostatectomy. 2 Additionally, PCa recurrence to the pelvic lymph nodes is best detected by PSMA PET-CT over other imaging modalities such as CT and MRI. 3,4
According to EAU Guidelines, PSMA PET-CT is now indicated to investigate biochemical recurrence after prostatectomy when PSA is greater than 0.2. 5 It can precisely locate sites of local disease recurrence for salvage therapy or oligometastases for MDT. MDT may delay the need for systemic therapy and can sometimes be curative. 6
- Ceci F, Uprimny C, Nilica B et al. (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; 42: 1284.
- Eiber M, Maurer T, Souvatzoglou M et al: Evaluation of hybrid (6)(8)Ga-PSMA Ligand PET/CT in 248 patients with biochemical recurrence after radical prostatectomy. J Nucl Med 2015; 56: 668.
- Giesel FL, Fiedler H, Stefanova M et al: PSMA PET/CT with Glu-urea-Lys-(Ahx)-[(6)(8)Ga(HBED-CC)] versus 3D CT volumetric lymph node assessment in recurrent prostate cancer. Eur J Nucl Med Mol Imaging 2015; 42: 1794.
- Sterzing F, Kratochwil C, Fiedler H et al: (68)Ga-PSMA-11 PET/CT: a new technique with high potential for the radiotherapeutic management of prostate cancer patients. Eur J Nucl Med Mol Imaging 2016; 43: 34.
- Mottet N, van den Bergh RCN, Briers E et al: EAU - ESTRO - ESUR - SIOG Guidelines on Prostate Cancer 2020. European Association of Urology 2020. Available at https://uroweb.org/guideline/prostate-cancer/.
- Bowden P, See AW, Frydenberg M et al: Fractionated stereotactic body radiotherapy for up to five prostate cancer oligometastases: interim outcomes of a prospective clinical trial. Int J Cancer 2020; 146: 161.