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Age 55 years optimal cutoff for staging thyroid cancer
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Using the cutoff age of 55 years was more appropriate for TNM staging in patients with differentiated thyroid cancer compared with 45 years, study data show.
According to researchers, the raised cutoff point could prevent inaccurate staging and over-aggressive thyroid cancer treatment.
“Age greater than 45 years is included as a staging variable for differentiated thyroid cancer in the American Joint Cancer Committee/Union for International Cancer Control TNM staging system, which has a higher predictive value of survival than others,” Mijin Kim, MD, of the department of internal medicine at Asan Medical Center, University of Ulsan College of Medicine in Seoul, and colleagues wrote. “However, the cutoff age of 45 years is controversial because this was a median age based on mostly outdated historical cohorts and has been adopted as a staging variable since the second edition of the TNM system. Several recent studies have demonstrated that 45 years may not be the most statistically robust cutoff age for this purpose.”
Kim and colleagues performed a cohort study of patients with thyroid cancer who underwent surgery at two care centers between 1996 and 2005 (n = 6,333), assessing cutoff points between 45 and 65 years for prediction of disease-specific survival. The researchers calculated the proportion of variation explained (PVE) and the Harrell’s c-index for each model to compare predictability. Median follow-up was 10 years.
Median patient age was 46 years, and 87% of participants were women; 60% (n = 3,810) of patients had stage I cancer, 2% stage II, 31% stage III and 7% stage IV. Kim and colleagues wrote that using the cutoff of 45 years, the 10-year disease-specific survival rate was 99.4% for stage I, 96.1% for stage II, 97.7% for stage III and 85.9% for stage IV (PVE = 3%; Harrell’s c-index = 0.693). With the 55-year cutoff, the disease-specific survival rate was 99.4% in stage I, 92.2% in stage II, 95.3% in stage III and 79.7% in stage IV (PVE = 4.3%; Harrell’s c-index = 0.776). When researchers used the age 55 cutoff, disease stage was downgraded among 20% of patients. An ROC curve analysis showed 55.4 years was the optimal cutoff for predicting disease-specific survival, with 76.4% sensitivity and 78.1% specificity (P < .001).
“Changing the cutoff age from 45 to 55 years led to down-staging of about 20% of patients and provided more accurate prognostic information for patients with stage IV disease,” Kim and colleagues wrote. “This change would prevent over-staging in low-risk patients and prevent over-aggressive treatment.” – by Andy Polhamus
Disclosures: The researchers report no relevant financial disclosures.
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