Strategy of neck dissection for early tongue cancer based on tumor invasion potential

tumor invasion potential: pT re-classification according to the UICC, 8th edition and evaluation of tumor invasion potential by the Yama-moto-Kohama （YK） classification were performed for 45 patients with pT1, 2N0 oral tongue cancers （UICC, 7th edition） who had undergone surgical resection as initial treatment followed by observation. Association between the two factors and late cervical metastases and survival rates were analyzed. The number of patients with pT1/2/3 （UICC, 8th edition） and YK-1, 2/3/4C, 4D was 17/20/8 and 10/18/17, respectively. The late cervical metastasis rate and 5-year disease-specific survival rate for pT1/2/3 were 29/45/63％ and 88/85/63％, and for YK-1, 2/3/4C, 4D were 10/39/65％ and 100/100/53％, respectively. Tumor invasion potential was more strongly associated with prognosis than pT classification （8th edition）. All of the low to moderately invasive YK-1-3 tumors were controlled by neck dissection after the appearance of late cervical metastasis, and therefore, the observation strategy seems to be appropriate for these tumors. In contrast, the highly invasive YK-4C, 4D tumors presented poor control rates by the observation strategy, and therefore, might need more intensive treatments such as additional neck dissection following primary tumor resection before late cervical metastasis appears.