The importance of correct stage grouping in oncology. Results of a nationwide study of oropharyngeal carcinoma in The Netherlands

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Abstract
Background. In the frame of a nationwide study of oropharyngeal carcinoma in the Netherlands (1986-1990), the current International Union Against Cancer 1992/American Joint Committee on Cancer 1988 staging system was evaluated with respect to patient distribution and prognostic value. Methods. Data related to epidemiology, treatment and survival from 640 patients referred for primary treatment were analyzed. Staging was first evaluated in a proportional-hazard regression analysis controlled for these data. Next, all possible combinations of T, N, and M were tested in a stepwise backward elimination model until all remaining indicator variables had a P value of less than 0.05. New stages were defined, based on the coefficients of the remaining indicator variables. Results. The revised stages revealed two advantages compared with the UICC 1992/AJCC 1988 version: a more balanced distribution of patients (31% in Stage I, 31% in Stage II, 18% in Stage III, 14% in Stage IV, and 5% unknown in the revised staging system versus 7% in Stage I, 17% in Stage II, 24% in Stage III, 50% in Stage IV, and 2% unknown in the UICC 1992/AJCC 1988 staging system), and an improved prognostic discrimination for the disease specific survival (5-year results in the revised staging were 67% in Stage I, 42% in Stage II, 28% in Stage III, and 11% in Stage IV, versus 68% in Stage I, 64% in Stage II, 44% in Stage III and 27% in Stage IV in UICC 1992/AJCC 1988). Conclusion. Improvements in the current staging system in patient distribution in the stages in prognostic discrimination is feasible by regrouping the T, N, and M but without redefining the categories themselves. Cancer 1995;75:2656–62.