PV-0432: Impact of Re-Irradiation Volume and Dose on the Survival of Recurrent HN Cancer: an AIRO Study

Purpose or ObjectiveThe most recent American Joint Committee on Cancer (AJCC 2017, eighth edition) staging manual modified the T classification of patients with tongue squamous cell carcinoma (SCC).Specifically, the presence of extrinsic tongue muscle invasion does not longer be classified as a T4 disease.However, this approach may be debatable as it can lead to tumor downstaging.To investigate whether this is actually the case, we designed a nationwide study to compare the clinical outcomes of Taiwanese patients with tongue SCC staged as pT3 versus pT4 based on the former AJCC 2010 seventh edition criteria.Patients with pT1 and pT2 tumors served as reference categories for survival analyses. Material and MethodsUsing data collected from the Taiwanese Cancer Registry Database between 2004 and 2012, we examined 8,509 patients with first primary tongue SCC who received surgery with or without adjuvant therapy.The distribution of T classification was as follows: pT1, n = 3,618; pT2, n = 3,043; pT3, n = 766; and pT4, n = 1,082. ResultsLess favorable 5-year outcomes were observed in patients with pT4 malignancies than in those with pT1-pT3 tumors (disease-specific survival [DSS], 53%/89%/74%/64%; overall survival [OS], 43%/82%/67%/56%, respectively, p <0.0001; pT4 versus pT3, p <0.0001).The presence of pT4 disease (versus pT3) was identified as an unfavorable independent prognostic factor for both DSS and OS. ConclusionPatients with pT4 tongue SCC have a less favorable prognosis than other T categories.Cases with tongue SCC and extrinsic muscle invasion should continue to be classified as having pT4 tumors.