AB188. Single center experience of diagnosis, treatment and prognosis of specialized stromal tumors of the prostate

Objective: Specialized stromal tumors of the prostate include stromal sarcoma and stromal tumors of uncertain malignant potential (STUMP). They are relatively rare and the clinical and prognostic features are unclear. Our study investigated diagnosis, treatment and prognosis of the disease.

Methods: We reviewed the clinical data of 13 patients diagnosed with specialized stromal tumors of the prostate from 2008 to 2015 in our department. A total of 12 patients were followed up, and we recorded the events of tumor recurrence, tumor progression, and cancer specific death.

Results: Patient age was 25 to 75 years (mean 50 years). The main clinical presentation included urinary obstructive symptoms (7/13), irritative symptoms (6/13), hematuria (5/13), rectal dysfunction (3/13) and prostate-specific antigen (PSA) elevation (2/13). Twelve patients underwent ultrasound examination which showed prostate neoplasm (n=3) and tumor beyond prostate (n=1). Eleven patients received pelvic MRI. Eight cases indicated prostate mass with enhancement, 1 case showed a mass outside prostate and 4 cases showed unclear boundaries with rectum. Of 8 patients taking prostate biopsy, 5 cases were diagnosed with STUMP, 1 case indicated stromal sarcoma and 1 case showed malignant tumor rising from prostatic stromal. Different treatments were used according to different conditions: 3 cases with pelvic exenteration, 3 cases with radical prostatectomy, 2 cases with radical prostatectomy after TURP, 2 cases with TURP, and 2 cases with prostate biopsy alone. Pathological diagnosis after surgery showed 4 cases of stromal sarcoma, 1 case of STUMP associated with sarcoma and 8 cases of STUMP. The median follow-up time was 32 months [2-55]. Among 
4 patients with stromal sarcoma, 1 patient died 3 months after surgery because of the disease, and the others survived for 
38-55 months without recurrence and metastasis. The patient with STUMP and sarcoma was alive with recurrence and metastasis 3 months after operation. Among 8 patients with STUMP, 1 patient suffered recurrence 5 months following operation and received pelvic exenteration with the pathology showing stromal sarcoma and died 7 months later. The others survived for 2-35 months, with 1 case recurring 16 months after radical prostatectomy, 1 case recurring 12 months and 23 months 
after each TURP respectively. There was no evidence of progression of disease for 2 cases of STUMP after biopsy.

Conclusions: Specialized stromal tumors of the prostate are clinically rare and have unspecific clinical manifestations. The diagnostic accuracy of biopsy is limited. The prognosis of stromal sarcoma is poor. The prognosis of STUMP is relatively well, but it still has the potential to recur or even become stromal sarcoma, which needs close follow-up.

Keywords: Stromal tumors; prostate; diagnosis; prognosis