Localization and restaging of carcinoma prostate by 68Gallium prostate-specific membrane antigen positron emission tomography computed tomography in patients with biochemical recurrence

Abstract

Introduction: Radical prostatectomy (RP) and radical radiotherapy (RT) are well established primary curative options for localized prostate cancer. Despite technical improvements, prostate-specific antigen (PSA)-recurrence after RP and RT is a common clinical scenario. We aimed to assess the role of ⁶⁸Gallium (⁶⁸Ga) prostate-specific membrane antigen positron emission tomography computed tomography (PSMA PET/CT) in patients with biochemical recurrence of prostate cancer after RP or RT for the detection and localization recurrent and metastatic disease.

Materials and methods: We ambispectively (70 retrospective and 100 prospective) analyzed the data of men with biochemical recurrence post-RP and post-RT who were evaluated by ⁶⁸Ga PSMA PET/CT at our institute. We aimed to assess the relationship between serum PSA levels and the probability of having a positive scan in patients with recurrent prostate cancer.

Results: The study included 170 men, all had adenocarcinoma of the prostate, 124/170 had previous RP and 46/170 had prior RT. The median serum PSA in the RP group was 1.8 ng/ml and 5.2 ng/ml in the RT group. In the post-RP cohort, the detection rate of ⁶⁸Ga PSMA PET/CT was 39.3% for PSA 0.2 to <0.5 ng/ml, 47.3% for PSA 0.5 to <1 ng/ml, 68.4% for PSA 1 to <2 ng/ml and 93.1% for PSA ≥2 ng/ml. In the post-RT group, the detection rate was 88.8% for PSA 2 to <4 ng/ml and 100% for PSA ≥4 ng/ml.

Conclusions: ⁶⁸Ga PSMA PET/CT provides a novel imaging modality for the detection of prostate cancer recurrence and metastases at low posttreatment PSA levels, which may help in directing appropriate salvage treatments.

Figure 1

A 61-year-old male, known case of adenocarcinoma prostate (Gleason's score 8), post radical prostatectomy with pelvic lymphadenectomy and raised serum prostate-specific antigen ~3.8 ng/ml. ⁶⁸Gallium-prostate-specific membrane antigen positron emission tomography computed tomography images show prostate-specific membrane antigen avid ill-defined lesion in the prostatic bed region (a-e) and prostate-specific membrane antigen avid abdomino-pelvic lymph nodes (a and f-i)

Figure 2

A 74-year-old male, known case of adenocarcinoma prostate (Gleason's score 6), post radiotherapy with rising serum prostate-specific antigen (9.5 ng/ml from 0.72 ng/ml). ⁶⁸Gallium-prostate-specific membrane antigen positron emission tomography computed tomography images, show prostate-specific membrane antigen avid ill-defined lesion in the prostate gland (b and c) and prostate-specific membrane antigen avid lymph nodes in the right iliac region (a, d and e)

Figure 3

A 62-year-old male, known case of carcinoma prostate (Gleason's score 6), post radiotherapy with raised serum prostate-specific antigen ~2.78 ng/ml. ⁶⁸Gallium-prostate-specific membrane antigen positron emission tomography computed tomography revealed prostate-specific membrane antigen avid ill-defined lesion in the prostate gland (b and c) and prostate-specific membrane antigen avid sclerotic lesion in the left 5^th rib (a, d and e)

Figure 4

A 67-year-old male, known case of adenocarcinoma prostate (Gleason's score 6), post radical prostatectomy with raised serum prostate-specific antigen ~5.2 ng/ml, diagnosed with prostate-specific membrane antigen avid lung nodules in the initial baseline study, on hormonal treatment since 1 year, follow-up ⁶⁸Gallium-prostate-specific membrane antigen positron emission tomography computed tomography was done for rising serum prostate-specific antigen (13.2 ng/ml from 5.2 ng/ml). Comparative ⁶⁸Gallium-prostate-specific membrane antigen positron emission tomography computed tomography study, showed increase in size, number, and prostate-specific membrane antigen avidity in the right lung nodules in the follow-up study (b, e, f, i and j) on comparison with the baseline study (a, c, d, g and h)

Figure 5

A 73-year-old male, known case of adenocarcinoma prostate (Gleason's score 7) status; post robotic radical prostatectomy with raised serum prostate-specific antigen 1.04 ng/ml. Diagnosed with bone metastasis to L2 vertebra in the initial baseline ⁶⁸Gallium-prostate-specific membrane antigen positron emission tomography computed tomography, post stereotactic radiotherapy to L2 vertebra and on hormonal treatment. Follow-up ⁶⁸Gallium-prostate-specific membrane antigen positron emission tomography computed tomography was done to assess the treatment response which showed increase in the extent of sclerosis with reduction in prostate-specific membrane antigen avidity of the lesion in the follow up ⁶⁸Gallium-prostate-specific membrane antigen positron emission tomography computed tomography (b, e and f) on comparison with the baseline (a, c and d)