Much of what we know about the epidemiology of musculoskeletal tumors is derived from retrospective series collected at large teaching centers1. The SEER (Surveillance, Epidemiology, and End Results) database is a validated national epidemiologic surveillance system and cancer registry that has been used to evaluate the treatment outcomes of various cancers. As noted by the authors, this database has been used to report the outcome of several malignant diseases, including breast, colorectal, prostate, and lung cancers. The authors have evaluated the SEER data on chondrosarcoma with the hope of identifying the demographics, prognostic factors, and natural history of chondrosarcoma.
The SEER database contains the demographic characteristics of the patients (the location, histological characteristics, and grade of tumors) and information regarding the surgical stage, the use of surgery and/or radiation treatment, and survival. The authors grouped chondrosarcomas from the SEER database into low-grade tumors (ICD-O-3 [International Classification of Diseases for Oncology, Third Edition] Grades 1 and 2) and high-grade tumors (ICD-O-3 Grades 3 and 4). However, it is important to note that the grading of cartilage lesions remains difficult and controversial.
The Skeletal Lesions Interobserver Correlation among Expert Diagnosticians (SLICED) Study group recently attempted to quantify the interobserver reliability of the determination of grade for cartilaginous lesions among a group of experienced musculoskeletal pathologists and radiologists. They concluded that the reliability associated with the grading of cartilage lesions, even among experienced clinicians, is low2. Thus, one may question the accuracy of the grades of chondrosarcomas from the SEER database—a database derived from seventeen population-based cancer registries—and this may make it difficult to generate conclusions from such a database with regard to outcome and prognosis based on grade.
Although most tumors in the SEER database were classified as chondrosarcoma NOS (not otherwise specified), the authors were able to create a histological profile of tumor subtypes and their associated five-year survival rates. The five-year survival rate that was associated with these subtypes was found to vary widely, from 0% (dedifferentiated) to 100% (clear cell). Although it is not surprising that the highest-grade lesions were associated with a statistically worse prognosis, this information is helpful, given the rarity of these diseases and the numbers amassed in the SEER database. However, further clarification would be beneficial. Mesenchymal chondrosarcoma and dedifferentiated chondrosarcoma are two rare entities against which neoadjuvant chemotherapy is often employed. If the five-year survival rate associated with these entities is 0% despite the use of chemotherapy, then, as stated in the article, the question arises whether chemotherapy, given its substantial toxicities, is beneficial. Unfortunately, the authors did not offer a conclusion regarding the efficacy of adjuvant therapy in treating these high-grade lesions.
Specific information on the type of surgery performed and the adequacy of surgical margins is not included in the SEER database. Thus, the authors were unable to evaluate how the treatment of chondrosarcoma affected survival and outcome. The treatment of chondrosarcoma is still evolving. Specifically, the ideal surgical treatment of low-grade chondrosarcoma remains controversial. Recently, several investigators have evaluated the treatment of these lesions3. They concluded that, although intralesional procedures for low-grade chondrosarcoma were associated with a significantly higher rate of local recurrence, they did not influence the overall survival rate or the rate of metastasis. Although the authors did not compare the specific treatments of these low-grade lesions (amputation versus resection versus curettage), their conclusion regarding the lack of change noted in the disease-specific survival plot may confirm that less-invasive management of these low-grade lesions, which is now gaining favor, does not affect the overall survival.
Recurrence of chondrosarcoma remains an important problem. With low-grade lesions, local recurrence has not been shown to be associated with the development of metastatic disease or to affect the overall prognosis. However, recurrence of high-grade lesions has been shown to be negatively associated with survival. As the authors point out, the lack of information in the SEER database regarding treatment provided after four months eliminates any potential information on patients who have had multiple operations. These factors been shown to have importance with regard to recurrence, metastasis, and survival. This information would be helpful for physicians not only in their decision-making but also in the counseling of their patients regarding surgical options and the outcome of these options.
The authors report sex-related differences in the incidence and associated survival rate of chondrosarcoma. The present series reveals a higher proportion of appendicular chondrosarcomas in women than in men. Unfortunately, tumor location is not well described in the database. Chondrosarcomas of the hand have been shown to have a female predominance. These lesions tend to have an ominous histologic appearance but a low metastatic potential4,5. It may be the case that chondrosarcomas of the digits not only account for the greater proportion of the appendicular lesions seen in women in this study but also for the better survival rate seen in women in this series. Thus, it would be helpful if specific bones were included as subcodes within the broader categories in the SEER database.
The greatest advantage of the present study is its size and the breadth of available patient demographic information and long-term follow-up data. The deficiencies in the database, however, serve to emphasize the difference between our knowledge about musculoskeletal malignant neoplasms and the other solid-tumor malignant diseases (i.e., of the breast, lung, and prostate). This study has shown some of the important deficiencies in the SEER database regarding outcomes of these musculoskeletal neoplasms. It is the correction of these deficiencies that will improve the quality of the data collected and allow for further evaluation of these rare diseases.
*The author did not receive any outside funding or grants in support of her research for or preparation of this work. Neither she nor a member of her immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.
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2. Skeletal Lesions Interobserver Correlation among Expert Diagnosticians (SLICED) Study Group. Reliability of histopathologic and radiologic grading of cartilaginous neoplasms in long bones. J Bone Joint Surg Am. 2007;89:2113-23.
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