Residual tumor (R) classification and prognosis.

The tumor status following treatment is described by the residual tumor (R) classification: R0, no residual tumor; R1, microscopic residual tumor; R2, macroscopic residual tumor. Residual tumor may be found in the area of primary tumor and its regional lymph nodes and/or at distant sites. The R classification reflects the effects of treatment and influences further treatment planning. Furthermore, the R classification is a strong predictor of prognosis. An acceptable long-term prognosis can be expected only in R0 patients. Although there exist clear correlations between stage and R classification the differences in prognosis of R0 versus R1,2 cannot be explained by differences in stage alone. The prognostic significance of R classification is demonstrated by respective data for non-small cell lung carcinoma, squamous cell carcinoma of oesophagus, gastric carcinoma, ductal adenocarcinoma of the pancreas, colorectal carcinoma, lung and liver metastases.