International Journal of Radiation Oncology*Biology*Physics
Clinical InvestigationPrognostic Impact of the 6th and 7th American Joint Committee on Cancer TNM Staging Systems on Esophageal Cancer Patients Treated With Chemoradiotherapy
Introduction
Staging systems for cancer have evolved over time and continue to change as knowledge of cancer increases. The TNM staging system is one of the most widely used staging systems, and was based on the extent of the tumor (T), the extent of spread to the lymph nodes (N), and the presence of distant metastasis (M). Tumor stage is the most important prognostic factor for any type of cancer, and planning for optimal treatment is mainly decided according to tumor stage (1).
The TNM staging system was recently revised in the 7th edition of the American Joint Committee on Cancer/International Union Against Cancer (AJCC/UICC) cancer staging manual, which was published in 2009 (2). The main differences between the 6th and 7th editions include: 1) T is was redefined and T4 was subclassified as T4A and T4B and 2) regional lymph nodes were redefined. N was subclassified according to the number of positive regional lymph nodes, and 3) M was redefined. In addition, prognostic staging, including histological grade and cancer site, was defined for T1-3N0M0 patients.
The 7th edition staging system for esophageal cancer was also revised and was based on retrospective analysis of pathologic data from patients treated only by primary surgical resection (3). However, because of poor outcomes with surgery alone, the current treatment for esophageal cancer incorporates neoadjuvant chemotherapy or chemoradiother-apy (CRT) 4, 5, 6. Definitive CRT has been established as a curative treatment for esophageal cancer, and its clinical utility has been recently expanded 7, 8, 9. To our best knowledge, the prognostic impact of the 7th edition staging system has been not evaluated in detail for esophageal cancer patients undergoing CRT.
Therefore, the objective of the present study was to evaluate the prognostic impact of clinical staging in the 7th edition on esophageal squamous cell cancer patients treated with CRT. We performed two analyses: 1) the prognostic impacts of the TNM staging systems of the 6th and 7th editions were compared and 2) the prognostic impacts of stage and prognostic groups, which incorporate TNM, cancer site, and histological grade, on patients with Stage I and II cancers were also compared.
Section snippets
Patients
This was a retrospective cohort study of esophageal cancer patients treated with CRT at the Aichi Cancer Center Hospital between January 2003 and January 2009.There were a total of 301 patients who met the following inclusion criteria: 1) carcinoma of thoracic esophagus; 2) histological diagnosis of primary esophageal squamous cell carcinoma; 3) total radiation dose ≥50 Gy; 4) concomitant chemotherapy consisting of 5-fluorouracil and platinum agents; 5) no previous thoracic radiotherapy (RT);
Patient characteristics
Between January 2003 and January 2009, 513 consecutive patients with esophageal cancer received RT. There were 212 patients excluded from this analysis for the following reasons: adenocarcinoma (n = 15), small-cell carcinoma (n = 1), carcinoma of cervical esophagus (n = 40), total radiation dose <50 Gy (n = 45), underwent RT alone (n = 37), underwent primary endoscopic mucosal resection (n = 23), chemotherapy other than 5-fluorouracil and platinum (n = 18), and missing analysis data (n = 33).
Discussion
Although neoadjuvant chemotherapy, CRT followed by esophagectomy, or CRT as definitive treatment have been standard therapies for resectable esophageal squamous cell cancer 4, 5, 6, 7, 8, 9, the 7th edition of the AJCC/UICC cancer staging system for esophageal cancer was based on pathologic data from esophageal cancer treated by primary surgical resection alone (3). However, pathologic staging criteria have been thought to be inadequate for patients receiving neoadjuvant therapy, including CRT
Acknowledgment
We appreciate the statistical advice and expertise of Keitaro Matsuo.
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Conflicts of interest: none.