Chordoma is a rare bony tumor, afflicting approximately 300 persons a year in the United States. ¹ These lesions are thought to arise from transformed remnants of the fetal notochord and account for approximately 2 to 3% of all bony cancers. ¹ The relative rarity of this disease has made study of the factors associated with risk and survival difficult, with no environmental factors identified to date. ² Over the years, several small registry-based series have been reported outside of the United States, but none includes more than 100 cases. ^{3,​4,​5,​6,​7} Within the United States, two groups ^8,​9 have reported on these lesions using population-based data drawn from the National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results (SEER) Program. The first ⁸ examined all chordomas using data available through 1995, whereas a second group ⁹ focused specifically on spinal chordomas using data available through 2003. As almost two decades have passed since the last complete examination of these tumors, in this chapter, updated information is provided on the patient characteristics, patterns of care, and survival for both cranial and spinal chordomas using data drawn from the NCI’s SEER Program during the years 1973 to 2011.

2.2 Methods

2.2.1 Data

The data are drawn from the SEER Program of the NCI. ¹⁰ The SEER Program is a population-based tumor registry that contains data covering from approximately 10 to 26% of the U.S. population depending on the year. Information concerning primary tumor type, patient demographics, initial cancer treatments, and survival is collected in the database. Data from the most recent SEER data set, from 1973 to 2011, were used for this analysis.

We include the 912 patients diagnosed between 1973 and 2011 with a histologically confirmed chordoma (International Classification of Diseases for Oncology third edition [ICD-O-3] code 9370). In an effort to examine a homogenous study population and to reduce the probability of including individuals with metastatic lesions, individuals with more than one primary cancer (i.e., a chordoma and a cancer of another site) were excluded from these analyses, as were patients diagnosed at death (autopsy only).

Both cranial and spinal sites of presentation are included in these analyses. Cranial sites were defined to include the oropharynx (ICD-O-2 code C103), nasopharynx (C111, C112, C119), pharynx (C140, C148), bones of the skull and face (C410), connective, subcutaneous, and soft tissues of the head (C490), cerebral meninges (C700), and any brain structures (C710–719, C722–725, C751–753, C760). Spinal sites were defined to include bones of the spine exclusive of the sacrum and coccyx (C412), the spinal cord (C720), posterior mediastinum (C382), and connective, subcutaneous, and soft tissues of the thorax or trunk (C493, C496). Sacral sites included bones of the sacrum and coccyx (C414), connective, subcutaneous, and soft tissues of the pelvis (C495), and pelvis not otherwise specified (C763). As the focus of this analysis is on lesions likely to include the central nervous system, the extra-axial sites, that is, long bones of the lower limb (C402) and connective tissues of the upper limb and shoulder or other unspecified sites (C491, C499), were not included. Information on sex, race, age, and year of diagnosis was available, as was information regarding whether the patient had received surgical resection (yes/no) and/or radiation therapy (yes/no) as part of the first course of treatment. Treatment parameters after the first course were not available in these data nor were specifics of chemotherapy regimes. Race was defined according to SEER categories of white, black, and other due to small sample sizes in the nonblack and nonwhite categories. Age was utilized as a continuous variable in the proportional hazards model. The primary outcome variable was time to death as measured in years.

2.2.2 Statistics

Comparison of cases by descriptor variables was done using a chi-square test, Fisher’s exact test, or unadjusted odds ratios (with 95% confidence intervals) for discrete variables and a t-test for continuous variables. Estimates of survival probabilities (with 95% confidence intervals) were calculated using Kaplan–Meier product limit methodology and compared using a Wilcoxon log-rank test. Hazard rates were computed using a Cox proportional hazards model. All analyses were completed using the SAS statistical software version 9.3. ¹¹

2.3 Results

Descriptive data for the sample are provided overall and by anatomical site in ▶ Table 2.1. The mean age at diagnosis is 52.7 (SD = 19.7) and varies significantly by anatomical site (p < 0.01), with cranial cases diagnosed at the youngest mean age (45.9 years) and sacral cases at the oldest mean age (60.9 years). The majority of cases are white (87.7%) and male (60.1%). In terms of anatomical site, 41% of cases are defined as cranial, with the remainder of cases split between spinal (30.0%) and sacral (28.5%) locations. Although the higher proportion of males relative to females was noted for all three anatomical sites, this sex difference varied significantly by anatomical site, with males representing 55.6% of cranial cases versus 59.5% and 67.3% of spinal and sacral cases, respectively (p < 0.01). The predominant anatomical site also varied significantly by race, with whites approximately half as likely as nonwhites to be diagnosed with a cranial versus a noncranial tumor (odds ratio [OR]: 0.52, 95% confidence interval [95% CI]: 0.35, 0.78).

The majority (84.5%) of patients received surgical treatment as part of the first course of treatment, although patients with disease of the sacrum were significantly less likely (73.3%) to receive surgery than were patients with cranial (90.9%) or spinal (86.0%) sites of disease (p < 0.01). Approximately 44% of patients received some form of radiation therapy at first course of treatment; this did not differ by anatomical site. Of note, receipt of treatment did not differ by race or sex.

Across all anatomical sites, the median survival is 4.7 years (mean survival is 6.1 years), although some patients survived for as long as 20 years. At 5, 10, 15, and 20 years from time of diagnosis, 67% (1.7% [SE]), 43.8% (2.0%), 32.0% (2.2%), and 19.8% (2.5%) of patients, respectively, remained alive ( ▶ Fig. 2.1, ▶ Fig. 2.2). When each of the risk factors (age at diagnosis, race, sex, anatomical site, decade of diagnosis, use of surgery, use of radiotherapy) was examined separately, survival was significantly associated with each factor with the exception of race ( ▶ Table 2.2). When these variables were considered jointly (multivariate model), survival varied significantly by age at diagnosis, sex, decade of diagnosis, and whether or not surgical treatment at first course was utilized. Improved survival was associated with female sex (hazard ratio [HR]: 0.80, 95% CI: 0.66, 0.98), young age at diagnosis (HR per year: 1.03, 95% CI: 1.02, 1.04), and use of surgery at first course of treatment (HR: 0.71, 95% CI: 0.55, 0.91). In addition, patients diagnosed and treated during the last two decades (1990–2011) versus during earlier years (1973–1989) showed an improved rate of survival, suggesting some improvement in treatment over time ( ▶ Table 2.2). After adjustment for the other factors, use of radiation therapy at first course of treatment, race, and anatomical site were not associated with overall survival.

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