New staging systems for functional and clinical severity are better at predicting outcomes of nonmetastatic papillary thyroid cancer (PTC) than the current American Joint Committee on Cancer (AJCC) system, researchers report.
"Survival estimates for patients with papillary carcinoma based on size of the tumor are inaccurate,” Dr. Jay F. Piccirillo from Washington University in St. Louis, Missouri, told Reuters Health by email. “The addition of patient age and comorbidity, or other diseases or illnesses that a patient has, provides important prognostic information.”
PTC has survival rates of 97% at five years and 93% at 10 years, and there is conflicting evidence regarding the prognostic impact of age, sex, burden of comorbidity and morphological spread of the tumor.
Dr. Piccirillo's team developed and validated a comprehensive functional-severity-staging system (FSSS) and clinical-severity-staging system (CSSS) for predicting five-year survival in patients with PTC.
Based on results from 774 patients, the FSSS incorporated increasing age and comorbidity into three stages: stage alpha, with a five-year survival of 99%; stage beta, with a five-year survival of 85%; and stage gamma, with a five-year survival of 66%.
They then consolidated FSSS and TNM pathological stage group into a three-stage CSSS: stage A, with a five-year survival of 95%; stage B, with a five-year survival of 74%; and stage C, with a five-year survival of 58%.
Using Siteman Cancer Center registry data, the CSSS outperformed the FSSS and the AJCC staging systems, the researchers report in JAMA Otolaryngology Head and Surgery, April 27. With National Cancer Database (NCDB) data, the CSSS had the largest overall survival gradient, but the FSSS performed best in all other evaluation measures.
“Our results suggest overdiagnosis is a major problem, with most papillary thyroid cancer patients experiencing an excellent prognosis,” Dr. Piccirillo said. “For young patients with no other illnesses and a small thyroid tumor, survival is excellent and consideration to watchful waiting approach is not unreasonable.”
Using these new systems, he said, “physicians can provide patients with more accurate estimates of survival by considering patient age and comorbidity."
“The FSSS and CSSS staging systems, compared with the AJCC, may improve the scientific reporting of disease outcomes and guide clinical care by improving classification of patients in clinically meaningful strata,” the researchers conclude. “In light of the overdiagnosis phenomenon, both the FSSS and CSSS can be useful tools to support comparative effectiveness studies and facilitate patient involvement in decision making.”