Robot-Assisted Laparoscopic Radical Prostatectomy 6 Months After Rectal Spacer Hydrogel Injection

Abstract

Background: SpaceOAR (organ at risk) hydrogel is a hydrogel matrix injected into the perirectal space posterior to the prostate for the purpose of mitigating radiation dose (and hence side effects of radiation) on the rectum. Manufacturer descriptions state that this material is reabsorbed 3 to 6 months after injection.

Case Discussion: We encountered a 75-year old male patient who underwent SpaceOAR injection in anticipation for primary external beam radiation treatment for intermediate risk prostate cancer (Gleason score 7 = 4 + 3, prostate specific Antigen [PSA] = 2.32, cT2a). After initiation of androgen deprivation, but before radiotherapy, the patient decided to no longer undergo radiation but rather elected to proceed with surgery. Based on the presence of the SpaceOAR, we delayed his surgery to 6 months after SpaceOAR injection to allow for absorption of the material. A preoperative MRI showed persistent hydrogel matrix in the perirectal space. We performed a robotic radical prostatectomy effectively despite the persistent SpaceOAR hydrogel by modifying our dissection closer to the prostate posteriorly.

Conclusion: SpaceOAR hydrogel may alter patient anatomy even 6 months after deployment, however, robotic prostatectomy would be feasible with proper knowledge of anatomy and by following the proper dissection planes above the perirectal space.

Case Discussion

History

This 75-year-old gentleman presented to our urology clinic in addition to radiation oncology for prostate cancer work-up. He has a significant family history of prostate cancer with a prostate specific antigen (PSA) ranging between 2.32 and 2.99.

Physical examination

Digital rectal examination revealed a suspicious prostate nodule cT2a otherwise unremarkable.

Diagnosis

He underwent TRUS biopsy of the prostate with pathology analysis revealing prostatic acinar carcinoma (Gleason score 7 = 4 + 3) that turned out to be intermediate risk prostate cancer as per the D'Amico risk stratification.

Intervention

After thorough discussion with the patient about his treatment options along with their risk and benefits, he planned to go for intensity modulated radiation therapy and androgen deprivation therapy. The patient underwent injection of the SpaceOAR hydrogel rectal spacer to anatomically displace his rectum away from his prostate and thus avoid rectal adverse events secondary to radiation therapy. After receiving androgen deprivation therapy (leuprolide), he decided against proceeding with radiation therapy and instead decided to undergo robot-assisted laparoscopic radical prostatectomy. The patient was counseled to delay the prostatectomy by 3 months to be beyond 6 months from SpaceOAR insertion. MRI performed 6 months after the SpaceOAR injection right before surgery showed the SpaceOAR was intact and undissolved (Figs. 1 and 2). We proceeded with robot-assisted laparoscopic radical prostatectomy with left intrafascial nervesparing and encountered the SpaceOAR intact while performing the posterior dissection of the rectum off the prostate. The rest of the procedure was otherwise standard with regard to the rest of the operative steps performed. Operative time was 326 minutes and estimated blood loss was 50 mL.

FIG. 1.

This is a T2-weighted axial MRI of the prostate showing the SpaceOAR hydrogel anterior to the rectum and posterior to the prostate remaining after 6 months of injection.

FIG. 2.

T2-weighted sagittal view showing the SpaceOAR hydrogel in between the prostate and rectum.

Follow-up

Patient's postoperative final pathology analysis revealed pT2N0Mx with negative margins and negative extra prostatic extension of tumor. The exact Gleason score was not determined because of the patient's history on Lupron and limited amount of tumor showing well-formed acini, atrophic acini, and poorly formed glands. His 3 months postoperative PSA was undetectable, he reports mild stress urinary incontinence (two pads per day), and erections were not yet adequate.

Topic discussion

SpaceOAR is a hydrogel consisting of water (90%) and polyethylene glycol (10%) manufactured by Boston Scientific designed to be injected into the perineum of the patient and hydrodissect the rectum away from the prostate to reduce the radiation received by the rectum. Thus, in patients with prostate cancer who plan on treatment with radiation therapy can safely create space between the prostate and rectum to decrease inadvertent radiation dose to the rectum and decrease risk of rectal adverse events.¹ The manufacturer information describes the SpaceOAR to last ∼3–6 months after which it would be resorbed and excreted in the patient's urine. Adverse effects with the procedure include pain, needle injury, or injecting the hydrogel in surrounding structures (bladder, prostate, urethra, and rectum), infection, inflammation, injection intravascularly, urinary retention, bleeding, and pelvic discomfort.¹ Acute pulmonary embolism, severe anaphylaxis, prostatic abscess and sepsis, purulent perineal drainage, rectal wall erosion, and rectourethral fistula were also reported.^1,2

We performed a literature review of similar cases of robotic prostatectomies performed after SpaceOAR injections, and none have been reported yet. Patients undergoing radical prostatectomy after SpaceOAR injection should be carefully approached since performing their posterior dissection would be quite challenging. During the robotic assisted laparoscopic radical prostatectomy after we began dissection of the seminal vesicles, we encountered the SpaceOAR hydrogel. Usually, the normal surgical anatomy posterior to the prostate consists of the posterior prostate capsule, under it the Denonvillier's fascia, below that the perirectal space containing the perirectal fat, and lastly the anterior rectal wall.³ Posterior dissection strategies include extrafascial dissection (plane created in the perirectal space separating anterior rectal wall from Denonvillier's and prostate), which is usually the preferred plane to enter in radical prostatectomies. Intrafascial dissection (surgical plane is created between the prostate capsule and Denonvillier's fascia) and interfascial dissection (creating a plane within Denonvillier's fascia by partially dissecting it) are usually done in select cases with low-/intermediate-risk tumors without any evidence of tumor extension or without high tumor volume on biopsy.³ Taking into account the distorted anatomy and the difficulty with creating the typical plane of dissection and that the hydrogel was found intact in the perirectal space, we proceeded with the posterior dissection intrafascially above Denonvillier's fascia close to the prostate capsule. That way we could avoid the distorted perirectal space and avoid the extra risk of entering the anterior rectal wall. Moreover, the SpaceOAR hydrogel was used as a landmark and as long as we remain above the hydrogel we are safe from rectal injury.

Conclusion

SpaceOAR is an interesting adjunct that is used to reduce rectal injury from radiation to the prostate, however, special consideration should be made for patients undergoing prostate surgery after insertion of the spacer. Even after 6 months of injection, the spacer was intact and the anatomy was altered. However, with proper knowledge of the anatomy and anticipation, interfascial or intrafascial dissection planes can be utilized to stay above the affixed matrix in the perirectal space rendering a robotic prostatectomy feasible in such cases.

Abbreviations Used

MRI

magnetic resonance imaging

PSA

prostate specific antigen

Disclosure Statement

Dr. S.E. is a consultant for Intuitive Surgical.

Funding Information

No funding was received for this article.

Cite this article as: Hout M, Sobel D, Pareek G, Elsamra S (2020) Robot-assisted laparoscopic radical prostatectomy 6 months after rectal spacer hydrogel injection, Journal of Endourology Case Reports 6:4, 454–456, DOI: 10.1089/cren.2020.0187.