Prostate cancer laparoscopic port site metastasis: A case report.

INTRODUCTION: Laparoscopic port site metastases are a rare but clinically important cause of biochemically recurrent prostate adenocarcinoma. C-11 choline, among other prostate-specific positron emission tomography (PET) radiotracers, has improved radiologist confidence in these otherwise difficult-to-detect sites of recurrence. PATIENT CONCERNS: A 62-year-old male presented with biochemically recurrent prostate adenocarcinoma after undergoing robotic-assisted radical prostatectomy 5 years earlier. DIAGNOSIS: C-11 choline positron emission tomography/computed tomography (PET/CT) demonstrated a choline-avid soft tissue nodule associated with a laparoscopic port site in the right rectus abdominis muscle, with correlative findings on prior magnetic resonance imaging, and biopsy confirming a prostate adenocarcinoma metastasis.
INTERVENTIONS: The patient was initiated on chemohormonal therapy. OUTCOMES: His prostate-specific antigen (PSA) became undetectable following chemohormonal therapy. A follow-up C-11 choline PET/CT demonstrated complete resolution of prior abnormal radiotracer activity in the right rectus abdominis muscle. LESSONS: Port site metastases in prostate adenocarcinoma are rare; however, those who treat prostate cancer patients should be aware of this phenomenon as the number of minimally invasive oncologic procedures increase. C-11 choline PET, among other prostate-specific PET probes, has become an important tool in evaluating patients with biochemically recurrent prostate adenocarcinoma, identifying site-specific metastases in a majority of patients.

Introduction

Prostate adenocarcinoma is the most common malignancy in men and will account for nearly 165,000 new cancer diagnoses in 2018 and approximately 29,000 deaths.[ Currently, radical prostatectomy and radiation therapy are the most common initial treatment options for prostate adenocarcinoma, providing definitive care in many patients.[ Laparoscopic techniques for oncologic surgeries, such as prostatectomy and pelvic lymphadenectomy, have now become commonplace.[ An unintended consequence of these laparoscopic procedures is port site metastases, a rare but clinically important cause of biochemically recurrent prostate adenocarcinoma.[ We present a rare case of a delayed port site metastasis 5 years after robotic-assisted radical prostatectomy, detected by C-11 choline, a prostate-specific positron emission tomography (PET) radiotracer.

Case report

A 62-year-old man presented with biochemically recurrent prostate adenocarcinoma and a prostate-specific antigen (PSA) level of 1.5 ng/mL. He underwent robotic-assisted radical prostatectomy five years earlier for Gleason 4 + 3 = 7 prostate adenocarcinoma (pT2a, pN0, MX). PSA remained detectable (PSA = 1.9 ng/mL) following surgery, prompting hormonal therapy and intensity-modulated radiation therapy to the prostatic fossa. His PSA following adjuvant therapy was undetectable but has since risen slowly and continuously. Restaging C-11 choline positron emission tomography/computed tomography (PET/CT) demonstrated a choline avid soft tissue nodule within the right rectus abdominis muscle, along a site of scarring and focal fatty replacement (Fig. 1A–D), raising suspicion for a port site metastasis. This focus of choline activity was better visualized on PET images reconstructed utilizing Q.Clear (GE Health Care, Chicago, IL), a Bayesian penalized-likelihood reconstruction algorithm (Fig. 1B and D). In retrospect, contrast-enhanced magnetic resonance imaging of the abdomen and pelvis performed 2 days earlier demonstrated an enhancing lesion in the right rectus abdominis muscle with diffusion restriction (Fig. 2A and B, arrows). Coronal images from a non-contrast CT of the abdomen and pelvis also demonstrated a soft tissue nodule in the same location (Fig. 2C, dashed circle). Core tissue samples from percutaneous ultrasound-guided biopsy of this lesion were positive for adenocarcinoma of prostate origin (Fig. 2D). After discussion with urology, patient elected to undergo treatment with chemohormonal therapy. His prostate-specific antigen (PSA) became undetectable following 6 cycles of chemotherapy and androgen deprivation. A follow-up C-11 choline PET/CT demonstrated complete resolution of prior abnormal radiotracer activity in the right rectus abdominis muscle. Application to the institutional review board for waiver of consent was submitted and accepted.

Figure 1

C-11 choline PET/CT with standard ordered subset expectation maximization reconstruction algorithm demonstrates subtle focal C-11 choline uptake in the right lower anterior abdominal wall at the site of an old laparoscopic port site (A and C, arrows). The degree of C-11 choline uptake is much more conspicuous with Q.Clear, a Bayesian penalized-likelihood reconstruction algorithm (B and D, arrows). PET/CT = positron emission tomography/computed tomography.

Figure 2

Magnetic resonance imaging of the abdomen demonstrates a focal area of diffusion restriction (A, arrow) in the right lower anterior abdominal wall with corresponding enhancement on post-gadolinium images (B, arrow). This correlated well with the area of C-11 choline uptake on the PET-CT. Coronal CT demonstrates a soft-tissue density mass at the laparoscopic port site (C, circle). The mass was subsequently biopsied with ultrasound guidance (D). PET/CT = positron emission tomography/computed tomography.

Discussion

Laparoscopic port site metastases represent early tumor recurrence developing locally within the abdominal wall at a prior trocar site; by definition port site metastases are not associated with peritoneal carcinomatosis.[ Port site metastases in laparoscopic urologic surgery are uncommon, with a reported incidence of 0.09% to 0.73%.[ This phenomenon is exceedingly rare in prostate adenocarcinoma, with only a limited number of reported cases to date.[ Proposed mechanisms for port site metastases include tumor cell spillage, direct inoculation during specimen removal, tumor cell aerosolization, and hematogenous dissemination.[ High grade, locally advanced disease may increase the risk for port site metastases, though this has not been confirmed.[ Minimally invasive techniques (conventional and robotic-assisted laparopic surgery) for radical prostatectomy are becoming increasingly popular because of data showing decreased bleeding, lower perioperative complication rates, and shorter post-operative recovery times, particularly for robotic-assisted radical prostatectomy.[

C-11 choline, among other prostate-specific PET radiotracers, has made a significant impact on the management of patients with biochemically recurrent prostate cancer by improving the sensitivity for detecting subcentimeter sites of metastatic disease over conventional anatomic imaging.[ Bayesian penalized reconstruction algorithms, such as Q.Clear, further increase image sensitivity by improving image quality and lesion contrast, particularly in patients with a high body mass index, when compared to the ordered subset expectation maximization reconstruction algorithm.[ Detecting site-specific metastases, such as port site metastases, in patients with biochemically recurrent prostate adenocarcinoma allows patients to be offered targeted therapy while simultaneously sparing them from unnecessary salvage radiotherapy to the prostatic fossa.[

Conclusion

We present a case of biochemically recurrent prostate adenocarcinoma secondary to a laparoscopic port site metastasis. Laparoscopic port sites are a very rare location for metastatic disease, particularly in patients with prostate adenocarcinoma. Prostate-specific PET-radiotracers, such as C-11 choline, have become an important tool in making this difficult, but clinically important diagnosis. Those involved in the care of prostate cancer patients should be familiar with port site metastases and the modalities used to image them.

Author contributions

Conceptualization: Michael C Jundt, Stephen M Broski.

Data curation: Michael C Jundt.

Project administration: Stephen M Broski.

Resources: Stephen M Broski.

Supervision: Stephen M Broski.

Writing – original draft: Michael C Jundt, Stephen M Broski.

Writing – review & editing: Michael C Jundt, Stephen M Broski.