Prognostic molecular biomarkers in chordomas: A systematic review and identification of clinically usable biomarker panels

Introduction and objective

Despite the improvements in management and treatment of chordomas over time, the risk of disease recurrence remains high. Consequently, there is a push to develop effective systemic therapeutics for newly diagnosed and recurrent disease. In order to tailor treatment for individual chordoma patients and develop effective surveillance strategies, suitable clinical biomarkers need to be identified. The objective of this study was to systematically review all prognostic biomarkers for chordomas reported to date in order to classify them according to localization, study design and statistical analysis.

Methods

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically reviewed published studies reporting biomarkers that correlated with clinical outcomes. We included time-to-event studies that evaluated biomarkers in skull base or spine chordomas. To be included in our review, the study must have analyzed the outcomes with univariate and/or multivariate methods (log-rank test or a Cox-regression model).

Results

We included 68 studies, of which only 5 were prospective studies. Overall, 103 biomarkers were analyzed in 3183 patients. According to FDA classification, 85 were molecular biomarkers (82.5%) mainly located in nucleus and cytoplasm (48% and 27%, respectively). Thirty-four studies analyzed biomarkers with Cox-regression model. Within these studies, 32 biomarkers (31%) and 22 biomarkers (21%) were independent prognostic factors for PFS and OS, respectively.

Conclusion

Our analysis identified a list of 13 biomarkers correlating with tumor control rates and survival. The future point will be gathering all these results to guide the clinical validation for a chordoma biomarker panel. Our identified biomarkers have strengths and weaknesses according to FDA’s guidelines, some are affordable, have a low-invasive collection method and can be easily measured in any health care setting (RDW and D-dimer), but others molecular biomarkers need specialized assay techniques (microRNAs, PD-1 pathway markers, CDKs and somatic chromosome deletions were more chordoma-specific). A focused list of biomarkers that correlate with local recurrence, metastatic spread and survival might be a cornerstone to determine the need of adjuvant therapies.

Long-term outcome of adjunctive Gamma Knife radiosurgery in skull-base chordomas and chondrosarcomas: An Indian experience

Skull-base chordomas (CD) and chondrosarcomas (CS) are locally-invasive tumors, have similar clinical presentations, while differing in their nature of growth and outcomes. In this study, we compare the long-term outcomes of Gamma Knife Radiosurgery (GKRS) as an adjunctive treatment modality for residual skull-base CD and CS. A retrospective analysis of clinico-radiological, pathological, radiotherapeutic and outcome data was carried out in patients who underwent adjunctive GKRS for residual skull-base CD and CS at P D Hinduja Hospital, Mumbai, between 1997 and 2020. All 27 patients included had either histopathologically proven CD (20 patients) or CS (7 patients). Brachyury immunohistochemistry in CD specimens gave 70.6% positivity. Total sessions of GKRS in CD and CS groups were 22 and 7, respectively. Mean tumor volume and mean margin dose in CD group were 6.53 ± 4.18 cm3 and 15.95 ± 1.49 Gy respectively, while for CS group, they were 4.16 ± 2.79 cm3 and 18.29 ± 3.15 Gy. With mean follow-up periods of 5.25 ± 4.73 years and 6 ± 2.07 years respectively, the CD and CS groups showed 5-year progression free survival (PFS) of 56.8% and 57.1%, and a 5-year overall survival (OS) of 82.1% and 100%. Sub-group analysis in both CD and CS groups revealed a better 5-year PFS with the following factors - CS histopathology, patient age < 45 years, margin dose > 16 Gy, tumor volume < 7 cm3 (p-value < 0.05), gross total resection, and brachyury positivity. Adjunctive radiotherapy for skull-base CD and CS holds promise.

Development of a Novel Orthotopic Primary Human Chordoma Xenograft Model: A Relevant Support for Future Research on Chordoma

Chordomas are slow-growing rare malignant neoplasms. The aim of this study was to establish a primary model of chordoma in the lumbosacral orthotopic area, to compare the growth rate to the subcutaneous site, and to show that this new graft site optimizes tumor growth and bony invasion. Eleven chordoma samples were transplanted subcutaneously in the flank and/or in contact with the lumbosacral region and grown into nude mice. Engraftment rate was significantly more successful in the lumbosacral environment compared with the flank at P0. Two xenografts from 2 patients showed bone invasion. One tumor was maintained through multiple rounds of serial transplantation, creating a model for study. Histological and immunostaining analysis confirmed that tumor grafts recapitulated the primary tumor from which they were derived, consisting of a myxoid chordoma expressing brachyury, cytokeratin AE1, EMA, and VEGF. Clear destruction of the bone by the tumor cells could be demonstrated. Molecular studies revealed PIK3CA and PTEN mutations involved in PI3K signaling pathway and most of the frequently reported chromosomal alterations. We present a novel orthotopic primary xenograft model of chordoma implanted for the first time in the lumbosacral area showing bone invasion, PIK3CA, and PTEN mutations that will facilitate preclinical studies.

Recent advances in understanding and managing chordomas

Chordomas are rare primary bone tumors arising from embryonic remnants of the notochord. They are slow-growing, locally aggressive, and destructive and typically involve the axial skeleton. Genetic studies have identified several mutations implicated in the pathogenesis of these tumors. Treatment poses a challenge given their insidious progression, degree of local invasion at presentation, and high recurrence rate. They tend to respond poorly to conventional chemotherapy and radiation. This makes radical resection the mainstay of their treatment. Recent advances in targeted chemotherapy and focused particle beam radiation, however, have improved the management and prognosis of these tumors.

Factors for tumor progression in patients with skull base chordoma

Skull base chordoma is a rare and fatal disease, recurrence of which is inevitable, albeit variable. We aimed to investigate the clinicopathologic features of disease progression, identify prognostic factors, and construct a nomogram for predicting progression in individual patients. Data of 229 patients with skull base chordoma treated by one institution between 2005 and 2014 were retrieved and grouped as primary and recurrent. Kaplan-Meier survival of progression was estimated, taking competing risks into account. Multivariable Cox regression was used to investigate survival predictors. The primary group consisted by 183 cases, gained more benefits on 5-year progression-free survival (PFS) (51%) and mean PFS time (66.9 months) than the recurrent group (46 cases), in which 5-year postrecurrent PFS was 14%, and mean postrecurrent PFS time was 29.5 months. In the primary group, visual deficits, pathological subtypes, extent of bone invasion, preoperative Karnofsky performance scale (KPS) score, and variation in perioperative KPS were identified as independent predictors of PFS. A nomogram to predict 3-year and 5-year PFS consisted of these factors, was well calibrated and had good discriminative ability (adjusted Harrell C statistic, 0.68). In the recurrent group, marginal resection (P = 0.018) and adjuvant radiotherapy (P = 0.043) were verified as protective factors associated with postrecurrent PFS. Factors for tumor progression demonstrated some differences between primary and recurrent cases. The nomogram appears useful for risk stratification of tumor progression in primary cases. Further studies will be necessary to identify the rapid-growth histopathological subtype as an independent predictor of rapid progression.