RB1 and chondrosarcoma: No significant difference was observed in protein expression of selected markers (Fig. 2c, Additional file 1: Figure S3), however three CDKN2A deletions (3/4) and one RB1 deletion (1/4) were found in the highly radioresistant group and none in the less radioresistant group indicating that a defective Rb pathway may be able to impair the response to γ-radiation in chondrosarcoma (Fig. 2d, Tables 1 and 2).