Intra-tumour heterogeneity is a common molecular phenomenon in metastatic clear cell renal carcinoma (mRCC), representing the genetic complexity of a tumour with multiple metastatic sites. The present commentary discusses the observed phenomena of phenotypic intra-tumour heterogeneity in mRCC patients treated with the tyrosine kinase inhibitors sunitinib or pazopanib. Here, drug response can be different on the level of each evaluated metastasis in the individual patient. This questions the currently used radiologic staging systems of RECIST criteria and demands for a modification of radiologic response assessment with the consequence of a patient-tailored therapy in the clinical setting.Please see related article: http://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-016-0729-9 .
Keywords: Intra-tumour heterogeneity; Metastatic clear cell renal carcinoma; Pseudoprogression; RECIST criteria; Response pattern; Tyrosine kinase treatment.