Clinical outcome of surgical management for symptomatic metastatic spinal cord compression from prostate cancer

We retrospectively assessed 19 patients who underwent decompression and reconstruction surgery for symptomatic MSCC from PC from 2002 to 2017 in Yokohama City University Medical Center and Yokohama City University Hospital. The indication for surgery was determined by multidisciplinary team management (shared decision-making among the patients, urologists, orthopedic surgeons, and radiation oncologist) under consideration of each patient’s prognosis, neurological deficits, and overall health status. In general, patients with a < 1-year prognosis and fixed neurological deficits were not recommended for surgery. The metastatic site and spinal cord compression were evaluated by computed tomography and magnetic resonance imaging. Before surgery for MSCC, all patients received high-dose dexamethasone as the initial treatment to prevent irreversible neurological impairment. Of the 19 patients included in the study, 8 had mHNPC and 11 had mCRPC. All patients had pathologically confirmed prostate adenocarcinoma. Clinical data were collected from each patient’s medical records. Tumor grades were classified by the Gleason grading system according to the 2014 International Society of Urological Pathology consensus [11].

The extent of disease on the initial bone scan [12] was used for objective semi-quantitative classification of the osseous metastases: 0 = normal or abnormal because of benign bone disease; 1 = fewer than 6 bony metastases, each of which is less than 50% of the size of a vertebral body (1 lesion about the size of a vertebral body was counted as 2 lesions); 2 = 6 to 20 bone metastases, sized as described above; 3 = more than 20 metastases but fewer than the number of metastases seen in a “superscan”; and 4 = “superscan” or its equivalent (i.e., more than 75% of the ribs, vertebrae, and pelvic bones). The surgical sites for MSCC were classified into five sites: the cervical spine, cervical-thoracic spine, thoracic spine, thoracic-lumbar spine, and lumbar spine.

The standard surgical procedures were posterior decompression and stabilization. Patients without mechanical instability and with preservation of sagittal alignment of the spine were treated by decompression alone, although the surgical procedures performed were at each surgeon’s discretion. An early rehabilitation program specific to the patient’s spinal cord injury was implemented. Postoperative radiation was not used in patients with mHNPC because primary androgen deprivation therapy was expected to be effective. In contrast, postoperative radiation was recommended for patients with mCRPC if the patient could tolerate radiation therapy.

The standard medical therapy for mHNPC was androgen deprivation therapy. No patients received cytotoxic agents or new androgen receptor-targeted therapy (abiraterone and/or enzalutamide) for mHNPC. After failed to CRPC, bisphosphonates or denosumab, new androgen receptor-targeted therapy, radium-223, or cytotoxic agents (docetaxel with steroids and/or cabazitaxel with steroids) were used if these agents were approved in Japan when the physician decided to use them. The treatment sequence for mCRPC was at the physician’s discretion.

The Frankel grading classification [13] was used for the functional evaluation preoperatively and 3 months postoperatively. The Frankel grading classification reveals the extent of the neurological/functional deficit caused by spinal cord injury and was established by Frankel et al. [13] in 1969. This classification system is divided into five grades: (A) no function, (B) sensory only, (C) some sensory and motor preservation, (D) useful motor function, and (E) normal. Frankel grades D and E indicate an ambulatory state.

The Kaplan–Meier product-limit method was used to estimate the overall survival (OS) distribution after surgery for MSCC. All analyses were conducted using IBM SPSS Statistics software for Windows, version 24 (IBM Corp., Armonk, NY, USA).

The experimental procedures were conducted in accordance with the ethical standards of the Helsinki Declaration.

Table 1 shows the patients’ characteristics. The median age of the patients with mHNPC and mCRPC at the time of surgery for MSCC was 72 and 65 years, respectively. The median prostate-specific antigen concentration at the diagnosis of MSCC in patients with mHNPC and mCRPC was 910 and 67 ng/mL, respectively. The sites of decompression surgery in patients with mHNPC were the thoracic spine in six (75.0%) patients and the lumbar spine in two (25.0%), and those in patients with mCRPC were the cervical spine in one (9.1%) patient, the cervical-thoracic spine in two (18.2%), the thoracic spine in six (54.5%), the thoracic-lumbar spine in one (9.1%), and the lumbar spine in one (9.1%). The median time to decompression surgery from symptom onset was 4 days in patients with mHNPC and 2 days in patients with mCRPC. Bone-targeted agents such as zoledronic acid and denosumab were used in four (36.3%) patients with mCRPC and no patients with mHNPC. Other variables at the initial diagnosis of PC are also listed in Table 1.

Table 2 shows the functional outcomes evaluated by the Frankel grade before and after decompression surgery among men with mHNPC. Although two of eight patients (25.0%) with mHNPC were ambulatory (Frankel grade D and E) preoperatively, six patients (75.0%) were ambulatory postoperatively. Table 3 shows the functional outcomes evaluated by the Frankel grade before and after decompression surgery among men with mCRPC. Among 11 patients with mCRPC, only 3 (27.3%) were ambulatory preoperatively while 6 (54.5%) were ambulatory postoperatively.

Figure 1a shows the Kaplan–Meier curve for OS after decompression surgery in the entire cohort, and Fig. 1b shows the Kaplan–Meier curve among men with mHNPC and mCRPC. The median OS after decompression surgery in the entire cohort, men with mHNPC, and men with mCRPC was 17 months, not reached, and 8 months, respectively.