巨大攝護腺腺癌合併直腸侵犯卻低血清攝護腺抗原指數之罕見案例

蔡仕傑¹、顧明軒^{1, 2}、黃志賢^{1, 2}

¹臺北榮民總醫院泌尿部；²國立陽明交通大學醫學系泌尿學科及書田泌尿科學研究中心

A Rare Case of Giant Prostate Adenocarcinoma with Rectal Invasion

but Low Serum PSA Levels

Shi-Jie Tsai¹, Ming-Hsuan Ku ^{1, 2}, William J.S. Huang ^{1, 2}

¹ Department of Urology, Taipei Veterans General Hospital,

²Department of Urology, College of Medicine and Shu-Tien Urological Science Research Center,

National Yang Ming Chiao Tung University, Taipei, Taiwan

Introduction

Prostate sarcoma is frequently suspected if primary tumor volume were high, with locally-advanced features, absence of distant metastases and with low serum PSA level compared to prostate adenocarcinoma of similar features. Herein, we presented a rare case of prostate cancer over 9cm in largest diameter with rectal invasion yet with normal serum PSA level, which was managed as prostate sarcoma initially with surgical resection, but pathologic findings turned out pure prostate adenocarcinoma unexpectedly.

Care presentation

This 73-year-old male patient had no past history of systemic diseases. He presented to our emergency room in December 2022 due to difficult voiding for two weeks. Foley catheter was inserted and he was referred to our outpatient clinic for further evaluation. Digital rectal examination revealed very huge prostate with uneven surface. Serum PSA was 1.63ng/ml. Abdominal computed tomography (CT) disclosed an 8.4 x 7.9 x 9.0 cm mass with central necrosis is noted at rectovesical pouch with epicenter close to prostate gland, with obscured fat plane between prostate and rectum, ruled out prostate sarcoma with rectal invasion. Chest CT showed a 2.1cm irregular lesion in RUL with pleura traction, but the pathology of RUL needle biopsy reported benign entity. Whole body bone scan showed no bone metastasis. Colonoscopy showed external tumor invasion at anterior rectum, from 3cm above anal verge (AAV) untill 10cm AAV, compatible with urologic tumor with rectal invasion.

Therefore, after thorough discussion with the patient, radical cystoprostatectomy with ileal conduit reconstruction and rectum resection with end colostomy were performed. All gross tumors were resected and total blood loss was 2000 ml. The final pathology disclosed adenocarcinoma, Gleason score 5+4. The tumor cells were positive for CK, NKX3.1, and PSMA stain. Surgical margin was free of tumor. No evidence of neuroendocrine tumor nor sarcoma features was noted. Rectum specimen showed tumor involvement, and bilateral cut ends were also free of tumor. Total 14 pelvic lymph nodes were removed and none of them had cancer involvement. The final staging was pT4N0M0.

The post-operative course was complicated with small bowel perforation and poor wound healing, but after small bowel re-anastomosis and wound debridement operations, the patient recovered well and was discharged home. Serum PSA tests 24 days and 60 days after the surgery were within undetectable level.

Discussion

This case presented with unusual presentations of giant prostate adenocarcinoma over 9 cm in diameter with rectum invasion but with low serum PSA level. Biopsy was not recommended to the patient initially as prostate sarcoma was highly suspected by the clinical and radiological pictures. For patients with prostate sarcoma, complete surgical resection with negative margins remains the mainstay of treatment and represents the best chance of achieving cure ^[1]. Pure prostate adenocarcinoma was considered very unlikely then. After shared-decision making with the patient, we opted for en bloc resection with ileal conduit and end colostomy reconstruction per principles of sarcoma treatments.

The final pathology eventually disclosed prostate adenocarcinoma, Gleason score 5+4, without lymph node nor distant metastasis. According to current NCCN guideline, such very high risks group locally-advanced disease without distant metastases should receive EBRT + ADT instead of surgical resection. However, for prostate cancer of giant tumor size and accompanied with urinary retention and obstipation, the feasibility of radiotherapy is questionable. Patient will be under great risks of prostate bleeding, radiation cystitis, radiation colitis, or tumor lysis syndrome. Therefore, we believed that surgical resection is still a good choice for this patient on account of tumor controls as well as symptoms relief.

In conclusion, this is a rare case of giant locally-advanced prostate adenocarcinoma with rectal invasion, but with low serum PSA level. Further genetic sequencing may be studied to investigate whether this is a distinct phenotype of prostate cancer.

References

1. Musser JE, Assel M, Mashni JW, Sjoberg DD, Russo P. Adult prostate sarcoma: the Memorial Sloan Kettering experience. Urology. 2014 Sep;84(3):624-8