Medical records of consecutive patients with surgically treated primary oral SCC were reviewed between January 1985 to January 2019, enrolled patients must meet the following criteria: there was prior history of radiotherapy for NPC, and the latency between the diagnosis of oral SCC and the end of radiotherapy was not less than 3 years [13 (link),14 (link)]. Information regarding age, sex, operation record, treatment, and follow-up was collected and analyzed. All the pathologic sections were re-evaluated and patients were re-staged by the 7th edition American Joint Committee on Cancer classification.
To compare the survival between NPC survivors and sporadic oral SCC patients, patients with sporadic oral SCC were also reviewed during the same study period, each NPC survivor was matched with two sporadic oral SCC patients, the matching process was performed by age (±5 years), sex, primary tumor site, perineural invasion, lymphovascular invasion, smoker, disease stage (stage I/II vs. stage III/IV), neck node status (positive vs. negative), and tumor stage (T1/T2 vs. T3/T4) [11 (link)]. Perineural invasion was considered to be present if tumor cells were identified within the perineural space and/or nerve bundle, lymphovascular infiltration was positive if tumor was noted within the lymphovascular channels [15 (link)]. Drinkers were defined as those who consumed at least one alcoholic drink per day for at least 1 year [11 (link),16 (link)], smokers were defined as those smoked on a daily basis or had quit smoking for less than 5 years [11 (link)].
To compare the survival between NPC survivors and sporadic oral SCC patients, patients with sporadic oral SCC were also reviewed during the same study period, each NPC survivor was matched with two sporadic oral SCC patients, the matching process was performed by age (±5 years), sex, primary tumor site, perineural invasion, lymphovascular invasion, smoker, disease stage (stage I/II vs. stage III/IV), neck node status (positive vs. negative), and tumor stage (T1/T2 vs. T3/T4) [11 (link)]. Perineural invasion was considered to be present if tumor cells were identified within the perineural space and/or nerve bundle, lymphovascular infiltration was positive if tumor was noted within the lymphovascular channels [15 (link)]. Drinkers were defined as those who consumed at least one alcoholic drink per day for at least 1 year [11 (link),16 (link)], smokers were defined as those smoked on a daily basis or had quit smoking for less than 5 years [11 (link)].
