Survival prognostic factors for metachronous second primary head and neck squamous cell carcinoma.

We examined the overall survival rates of a national cohort to determine optimal treatments and prognostic factors for patients with metachronous second primary head and neck squamous cell carcinomas (mspHNSCCs) at different stages and sites. We analyzed data of mspHNSCC patients collected from the Taiwan Cancer Registry database. The patients were categorized into four groups based on the treatment modality: Group 1 (control arm; chemotherapy [CT] alone), Group 2 (reirradiation [re-RT] alone with intensity-modulated radiotherapy [IMRT]), Group 3 (concurrent chemoradiotherapy alone [irradiation with IMRT]), and Group 4 (salvage surgery with or without RT or CT). We enrolled 1741 mspHNSCC patients without distant metastasis. Multivariate Cox regression analyses revealed that Charlson comorbidity index (CCI) ≥6, stage of second HNSCC, stage of first HNSCC, and duration from first primary HNSCC of <3 years were significant poor independent prognostic risk factors for overall survival. After adjustment, adjusted hazard ratios and 95% confidence intervals for the overall all-cause mortality risk at mspHNSCC clinical stages III and IV were 0.72 (0.40-1.82), 0.52 (0.35-0.75), and 0.32 (0.22-0.45) in Groups 2, 3, and 4, respectively. A Cox regression analysis indicated that a re-RT dose of ≥6000 cGy was an independent protective prognostic factor for treatment modalities. CCI ≥ 6, stage of second HNSCC, stage of first HNSCC, and duration from first primary HNSCC of <3 years were significant poor independent prognostic risk factors for overall survival. A re-RT dose of ≥6000 cGy may be necessary for mspHNSCCs.