Atypical metastases from prostate cancer detected on 68Ga-PSMA PET/CT: a case series

CASES PRESENTATION

Prostate cancer (PCa) is one of the most frequent malignant tumors in men worldwide. The primary treatment of localized disease consists of radical prostatectomy and radiation therapy. Unfortunately, tumor recurrence after initial treatment is not uncommon and is suspected by the rise in prostate––specific antigen (PSA) levels. Distinguishing between a local recurrence and distant metastases is critical to define an effective therapy (¹).

The most common pattern of tumor spread involves abdominopelvic lymph nodes and the bones followed by the lung, liver, pleura, supradiaphragmatic lymph nodes and adrenal glands. Rarer metastatic sites may be observed in nearly any organ such as the brain, breast, diaphragm, gastrointestinal tract, skin, heart, penis and testicle (²–⁵).

Traditionally, PCa recurrence is investigated by prostate imaging such as computed tomography, magnetic resonance and bone scintigraphy. However, this approach has limited sensitivity particularly at low PSA levels (¹).

The recently introduced positron emission tomography/computed tomography (PET/CT) with the new tracer 68Ga-labeled prostate specific membrane antigen ligand (PSMA) has revolutionized the evaluation of patients with PCa recurrence. PSMA is a transmembrane enzyme which is significantly overexpressed in the majority of prostatic adenocarcinomas. PSMA expression rises with increasing tumor dedifferentiation, metastatic and hormone-refractory cancers. PET/CT with 68Ga-PSMA provides a high detection rate in the evaluation of local recurrence or metastatic disease with the summary sensitivity and specificity of 86% on per-patient analysis. PET/CT positive results increase with PSA level and shorter PSA doubling time (⁶–⁸).

However, to date, a few investigations have described rare sites of metastases from PCa detected by PET/CT with 68Ga-PSMA (9, 10).

We report a case series in which atypical sites of PCa metastases in mediastinal lymph nodes (Figure-1), rectum (Figure-2), testis (Figure-3), deferent duct (Figure-4), penis (Figure-5) and abdominal wall (Figure 6) were detected by PET/CT with 68Ga-PSMA. Of note, a single atypical metastasis was detected by PET/CT in each of three of the six reported cases (Figures 3, 4 and 6). In this context, PET/CT with 68Ga-PSMA had an effective role not only in the detection of the PCa metastasis but also in the treatment planning.

Figure 1
Mediastinal lymph nodes metastases.

Figure 2
Rectal metastasis.

Figure 3
Testicular metastasis.

Figure 4
Deferent duct metastasis.

Figure 5
Penile metastases.

Figure 6
Abdominal wall metastasis.

CONCLUSIONS

PET-CT with 68Ga-PSMA allows the detection of PCa metastases, including the rarer sites, proving its diagnostic value in the evaluation of the extent of the disease in patients with recurrence.

• Ethical approval
  This study was approved by the institutional Ethics Review Board.

REFERENCES

• ¹
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• ²
  Bubendorf L, Schöpfer A, Wagner U, Sauter G, Moch H, Willi N, et al. Metastatic patterns of prostate cancer: an autopsy study of 1,589 patients. Hum Pathol. 2000;31:578-83.
• ³
  Gandaglia G, Abdollah F, Schiffmann J, Trudeau V, Shariat SF, Kim SP, et al. Distribution of metastatic sites in patients with prostate cancer: A population-based analysis. Prostate. 2014;74:210-6.
• ⁴
  Vinjamoori AH, Jagannathan JP, Shinagare AB, Taplin ME, Oh WK, Van den Abbeele AD, et al. Atypical metastases from prostate cancer: 10-year experience at a single institution. AJR Am J Roentgenol. 2012;199:367-72.
• ⁵
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• ⁶
  Afshar-Oromieh A, Avtzi E, Giesel FL, Holland-Letz T, Linhart HG, Eder M, et al. The diagnostic value of PET/CT imaging with the (68) Ga-labelled PSMA ligand HBED-CC in the diagnosis of recurrent prostate cancer. Eur J Nucl Med Mol Imaging. 2015;42:197-209.
• ⁷
  Eiber M, Maurer T, Souvatzoglou M, Beer AJ, Ruffani A, Haller B, et al. Evaluation of Hybrid 68Ga-PSMA Ligand PET/CT in 248 Patients with Biochemical Recurrence After Radical Prostatectomy. J Nucl Med. 2015;56:668-74. Erratum in: J Nucl Med. 2016;57:1325.
• ⁸
  Perera M, Papa N, Christidis D, Wetherell D, Hofman MS, Murphy DG, et al. Sensitivity, Specificity, and Predictors of Positive (68) Ga-Prostate-specific Membrane Antigen Positron Emission Tomography in Advanced Prostate Cancer: A Systematic Review and Meta-analysis. Eur Urol. 2016;70:926-37.

Publication Dates

• Publication in this collection
  18 Nov 2020
• Date of issue
  Jan-Feb 2021

History

• Received
  02 Feb 2020
• Accepted
  29 Apr 2020
• Published
  10 Sept 2020