Occurrence of metachronous second primary cancer in head and neck cancer survivors: A systematic review and meta-analysis of the literature.

OBJECTIVE: Head and neck cancer (HNC) is the sixth leading cancer worldwide with approximately 600,000 new cases per year. Several studies suggest that HNC survivors may have an increased risk of developing second primary cancers (SPCs). A systematic review and meta-analysis was performed aiming to quantify the overall and site-specific risk of metachronous SPCs in HNC survivors. METHODS: PubMed, Web of Science and Scopus were searched to identify studies published until October 2019. Studies investigating the standardised incidence ratio (SIR) of metachronous SPC were included. A random-effects meta-analysis was performed to calculate the overall and site-specific SIRs. Newcastle-Ottawa Scale was used to assess the study's quality. Heterogeneity was quantified using the I2 statistics and explored using meta-regression. RESULTS: Twenty-six studies were included in the systematic review. Studies differed by the definition of metachronous SPC used. For the meta-analyses, the studies were grouped according to these definitions. In the three groups, the overall risk of metachronous SPC was increased. The highest SPC risk was for oropharynx, oesophagus and lung. CONCLUSIONS: Head and neck cancer survivors are at increased overall risk of metachronous SPCs. The canonical upper aerodigestive sites, HNLE (head and neck, oesophagus and lung), were the SPC sites with the highest risk. IMPLICATION FOR CANCER SURVIVORS: Our results emphasise the importance of targeted surveillance strategies aimed at early detection and tertiary preventive interventions.