Histologic Variability and Diverse Oncologic Outcomes of Prostate Sarcomas

Soft tissue sarcomas make up less than 1% of all cancers, and less than 5% of these lesions occur in the genitourinary tract [1, 2, 3]. Primary prostate sarcomas arise from nonepithelial mesenchymal components of prostate sarcoma [4]. These tumors account for less than 0.1% of primary prostate malignancies in adults [5, 6]. For the prostate gland, leiomyosarcoma is the most common histological type in adults, whereas rhabdomyosarcoma is more common in pediatric patients [4, 7, 8, 9]. Clinically, the tumors cause bladder outlet obstruction and often require surgical intervention to control local symptoms. Most patients present with both filling symptoms, such as frequency, urgency, dysuria, and nocturia, and voiding symptoms, such as a poor stream, hesitancy, terminal dribbling, and incomplete voiding. Less frequent manifestations are hematuria, perineal pain, rectal pain, and a burning sensation on ejaculation. Constipation and constitutional symptoms such as weight loss may also be present [1].

Surgery has long been the mainstay of treatment for soft tissue sarcoma and usually involves cystectomy or pelvic exenteration for more locally advanced lesions. Radical prostatectomy or more conservative surgery may be an option if the sarcoma is small and is confined to the prostate but this presentation is uncommon. The long-term survival of patients with prostate sarcomas is poor owing to local recurrence after surgery and chemo-radiation therapy [4, 10]. Because of the rarity of genitourinary stromal cell sarcoma, especially prostate sarcoma, clinical research on these tumors is limited and large institutional-based studies are unavailable [11]. In addition, because of the rarity of these cancers, prognosis is often considered to be unpredictable or highly variable and appears to be related to specific parameters, such as the tumor grade (high vs. low), tumor size (≤5 cm vs. >5 cm), and anatomical site (i.e., resectability) [1]. Hence, we here report the 24-year experience of a single institution with prostate sarcoma.

The rarity of adult prostate sarcoma is a major obstacle in the clinical research of this cancer, and contemporary data are therefore scarce [1, 3, 12]. Sexton et al. [4] reported 21 cases and Wang et al. [11] reported 25 cases of prostate sarcoma in reviews that spanned 3 decades, but these data included only adult prostate sarcoma, whereas our current data included pediatric to adult patients [2]. Russo [13] and Mondaini et al. [1] reported their experience with genitourinary sarcoma, but accurate comparison with our research was difficult because their prostate sarcoma patients were analyzed together with patients with other genitourinary sarcomas, including those of renal, bladder, seminal vesicle, and paratesticular origins.

Most prostate sarcomas cause urinary obstruction, and transurethral prostate resection performed because of symptoms of bladder outlet obstruction without elevation of PSA may reveal prostate sarcoma [7, 14]. Unlike renal sarcoma [15], prostate sarcoma is often suspected before surgery, especially when a young man presents with lower urinary tract obstruction, a markedly enlarged prostate, and a normal PSA value. In contrast with prostate adenocarcinoma, the PSA level is generally not elevated in patients with prostate sarcoma, which can be explained by the nonepithelial origin of sarcoma [16]. For most patients, the initial diagnosis can be preoperatively established by using image-guided needle biopsy, which is well tolerated, requires no anesthesia, and often provides adequate tissue for a histological diagnosis.

Clinical staging is further enhanced by cross-sectional pelvic imaging. MRI is the imaging modality of choice for extremity sarcomas [5]. For large prostate sarcomas, we believe MRI facilitates surgical planning by providing multiplanar images, better delineation of the soft tissue plane, and superior assessment of the relationship between the tumor and adjacent viscera and neurovascular structures. Various histological subtypes have been found. The most common subtype is spindle cell sarcomas. Other subtypes are rhabdomyosarcomas, synovial sarcoma, liposarcoma, Ewing sarcoma, stromal sarcoma, and nerve sheath tumor [17]. Comparison of the relationship between prognosis and the various subtypes has been difficult because of their rarity.

The overall survival rate for patients with prostate sarcoma is poor. Owing to the lack of an early screening method, specific clinical symptoms result in more advanced disease at presentation. The overall 5-year actuarial survival rate for our patients was 12%, compared with a range of 0% to 60% in other series [18, 19, 20]. However, comparison of data from various series is difficult because of a nonuniform method of reporting patient and pathological characteristics, changes over time in radiographic staging, and the relatively small number of patients with prostate sarcoma.

We determined whether various factors, including patient age, tumor grade, size, metastasis, and therapeutic procedures affected survival. However, we found no survival differences between patient groups in our study. We checked the overall survival of patients by use of univariate and multivariate analyses but found no valuable results owing to the various histologies and limited number of patients.

The prognosis is poor for patients with prostate sarcoma who are treated with surgery alone, and a multimodality therapy is thus strongly recommended [21]. The rare occurrence of prostate sarcoma has limited the critical evaluation of treatment strategies and patient survival to anecdotal experiences. However, our results suggest that there may be a survival advantage of treatment with a combined multimodality approach [22, 23]. Although there is no definite treatment strategy for prostate sarcoma, multimodality treatments that are likely to be more effective for patients with prostate sarcoma can be derived from existing protocol-based strategies for other sarcomas, such as retroperitoneal and pelvic sarcomas [24, 25]. Innovative, combined multimodality treatment strategies may help to improve prognosis for patients with these generally poor prognosis tumors.

Prostate sarcoma is a rare neoplasm that accounts for only 0.1% of prostate cancer cases. This cancer usually follows an aggressive clinical course, and the prognosis is generally poor, with a medial overall survival of 20 months in our series. Owing to a lack of screening for prostate sarcoma, early image-guided needle biopsy is recommended for patients with a suspected prostate sarcoma. With existing protocol-based strategies, proper management is needed for curative intent. Additional collaborative large-scale studies are necessary for appropriate management of this undesirable disease.