Primary Extradural Tumors of the Spine - Case Review with Evidence-guided Management

Background:

Primary extradural tumors of the spine comprise only a small percentage of all spinal tumors. However, given their relative radioresistance and their typical malignant, invasive nature, surgery may be associated with fairly high morbidity and mortality rates. Furthermore, it may be especially difficult to achieve gross total resections with tumor-free margins.

Case Descriptions:

We present two cases and review the literature regarding the presentation, diagnosis, and evidence-based guidance/treatment of primary extradural spinal tumors. The first patient with an L1 chordoma presented with cauda equina syndrome. Following surgery, the second patient, with a giant cell tumor of the cervicothoracic junction, responded well to the novel drug denosumab, a monoclonal antibody to the RANK ligand.

Conclusion:

Primary extradural spine tumors pose significant challenges to surgeons as the aim is to achieve satisfactory surgical outcomes with clean tumor margins (e.g, thus avoid recurrence) while minimizing morbidity. Improvements in radiotherapy, chemotherapy, and novel molecular drugs may increase survival rates and improve overall outcomes.

A role for maintenance therapy in managing sarcoma

Despite the use of recommended chemotherapy regimens, patients with metastatic sarcomas have a poor prognosis. To date, the median overall survival for metastatic disease remains less than 18 months. First-line treatment of most metastatic sarcomas consists of chemotherapy with or without surgical excision of residual disease, followed by "watchful waiting" until disease progression or recurrence. According to the current treatment paradigm, recommended by United States and European clinical guidelines, chemotherapy is administered for a fixed number of cycles, and then a watchful waiting approach is taken once a best response is achieved. Single-agent doxorubicin remains the standard for treatment of most soft-tissue sarcomas (STS), as combination and dose-intense regimens have largely failed to improve survival. Combination chemotherapy is the standard treatment approach for osteosarcoma and Ewing's sarcoma, but outcomes are poor for patients with recurrent disease. In order to improve outcomes (in particular, progression-free survival [PFS] and overall survival [OS]), strategies shown to be effective in other solid malignancies, such as maintenance therapy and long-term treatment with targeted therapy, are being investigated in patients with advanced sarcomas. One potential promising approach is the use of mammalian target of rapamycin (mTOR) inhibitors for maintenance therapy. One such mTOR inhibitor, ridaforolimus (AP23573, MK-8669), is currently being evaluated in patients with advanced bone and STS in the ongoing Sarcoma mUlti-Center Clinical Evaluation of the Efficacy of riDaforolimus (SUCCEED) trial.

Treating soft tissue sarcomas with adjuvant chemotherapy

Surgery remains the cornerstone of treatment and the only curative loco-regional approach of localized resectable soft tissue sarcoma (STS) in 2011: the usual first-line treatment is wide margin surgery plus radiotherapy, especially in the case of primary tumors arising in the limbs. An optimal initial R0 resection is one of the most reproducible and reliable prognostic factors for survival in resectable STS. Nevertheless, despite improved local control rates, more than half of the patients still develop and die from unresectable, locally advanced, and/or metastatic disease. Unfortunately, very few cytotoxic drugs have shown activity in this clinical setting with the exception of doxorubicin, ifosfamide, and to a lesser extent, dacarbazine. A conventional-dose, single-agent chemotherapy is still considered to be the standard treatment for metastatic disease. The impact of adjuvant chemotherapy after resection of a high-grade STS remains controversial due to the lack of reproducible impact on survival. Because STS is a rare disease, most trials have involved a relatively small number of patients, with heterogeneous groups of histological/molecular subtypes of sarcomas, initial sites of the disease, and patient's characteristics. In a few trials, a lower risk for local recurrence was observed among patients receiving adjuvant chemotherapy but without any significant gain in overall survival. A meta-analysis based on individual data of these randomized studies has confirmed a significant impact of adjuvant chemotherapy on relapse, either local or metastatic, but without any significant benefit on survival. It should be of importance to include the last recent large trials in a new meta-analysis of source data in order to more carefully analyze a possible benefit of systemic adjuvant chemotherapy in localized sarcoma. Until this study is performed, it is an obvious conclusion that adjuvant chemotherapy has not reproducibly demonstrated its capacity to improve overall survival and relapse-free survival in an unselected population of patients. In 2011, there is therefore an urgent need to determine whether or not there are small subpopulations of patients truly benefiting from adjuvant chemotherapy (with conventional agents), and to identify prospectively these populations. With the exception of male, older than 40 years, with a non-optimal resection of their primary (R1 resection) or in the subgroup of grade 3 STS, no other relevant clinical prognostic/predictive factors have been highlighted. The take home messages in 2011 could be as follows: (1) adjuvant chemotherapy is not recommended routinely in high-grade STS; (2) adjuvant chemotherapy is recommended in patients underwent a R1 resection and with a grade 3 STS; (3) adjuvant chemotherapy cannot rescue an inadequate initial surgery; (4) if selected, chemotherapy has to be contain anthracycline and fractionated adequate dose of ifosfamide (around 9 g/m(2) per cycle); (5) the era of adjuvant chemotherapy trials with the same chemotherapy regimen in all histological subtype of sarcoma is ended; and (6) prognosis of patients with a localized STS starts at diagnosis. The dramatic activity of imatinib in GIST, the heterogeneous outcome of each histological subtype of sarcomas akin to being different diseases, and the high sensitivity of some histological subtypes of sarcoma to specific agents clearly open a new era in the management and the evaluation of new agents in the field of STS. The design of the future adjuvant trials has to incorporate these new findings and new prognostic/predictive biomarkers in order to improve the as yet dismal prognosis of patients developing high-grade localized STS.

The epidemiology of malignant giant cell tumors of bone: an analysis of data from the Surveillance, Epidemiology and End Results Program (1975-2004)

Malignant giant cell tumor (GCT) of bone is a rare tumor with debilitating consequences. Patients with GCT of bone typically present with mechanical difficulty and pain as a result of bone destruction and are at an increased risk for fracture. Because of its unusual occurrence, little is known about the epidemiology of malignant GCT of bone. This report offers the first reliable population-based estimates of incidence, patient demographics, treatment course and survival for malignancy in GCT of bone in the United States. Using data from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program, we estimated the overall incidence and determinants of survival among patients diagnosed with malignant GCT of bone from 1975–2004. Cox proportional hazards regression was used to evaluate demographic and clinical determinants of survival among malignant GCT cases. Based on analyses of 117 malignant GCT cases, the estimated annual incidence in the United States was 1.6 per 10,000,000 persons per year. Incidence was highest among adults aged 20 to 44 years (2.4 per 10,000,000 per year) and most patients were diagnosed with localized (31.6%) or regional (29.9%) disease compared to distant disease (16.2%). Approximately 85% of patients survived at least 5 years, with survival poorest among older patients and those with evidence of distant metastases at time of diagnosis. The current study represents the largest systematic investigation examining the occurrence and distribution of malignancy in GCT of bone in the general U.S. population. We confirm its rare occurrence and suggest that age and stage at diagnosis are strongly associated with long-term survival.