The effect of preoperative therapy against advanced oral cancer. The pattern of residual cancer nests assessed with semiserial whole surgical specimens

Histological change of advanced oral cancers following concurrent chemoradiotherapy was examined with semiserial whole surgical specimens. Subjects included six tongue squamous cell carcinomas (SCCs), two oral floor SCCs and three lower gingival SCCs, and all the tumors were preoperatively treated by the combination of radiotherapy and superselective intraarterial infusion of carboplatin (CBDCA) or oral administration of TS-1. Clinical effect was assessed as complete response (CR) in three cases, partial response (PR) in five, minor response (MR) in two and no change (NC) in two. The distribution of residual cancer nests was categorized as the superficially-located and deeply-located patterns. It was noteworthy that the pattern of residual cancer nests and the histological effect were different between sections even in the same tumors. Furthermore, a few viable cancer nests were observed exclusively in the advancing edge in tumors assessed as Grade 2b (Oboshi-Shimosata classification), where most of the cancer nests were degenerative or necrotic. This finding suggests that the extent of resection could not be reduced even in tumors that responded well to preoperative therapy. In the present cases, the histological effect of chemoradiotherapy was evaluated as Grade 4a in two cases, Grade 2b in four, Grade 2a in five and Grade 1 in one. Tumors of the PR showed a wide variation of histological evaluation from Grade 1 to Grade 4a, resulting in a discrepancy between the clinical and histological evaluations. (author)