Second cancer incidence and risk factors in patients with salivary gland cancers.

ABSTRACT

IMPORTANCE Second primary cancers (SPCs) are common in patients with head and neck squamous cell carcinoma, while the incidence and risk factors of SPC in patients with salivary gland cancers (SGCs) are largely unknown. This study aimed to examine the incidence of and risk factors for SPC in patients with SGC. OBJECTIVE: To report the risk factors and incidence of SPC in patients with SGC and compare them with the values of newly developed cancers (NDCs) in a healthy population. DESIGN, SETTING, AND PARTICIPANTS: A retrospective case-control study conducted at a university teaching hospital. The study population comprised 184 patients with SGC, without a history of cancer, who were treated between 2000 and 2010 and followed up for at least 2 years, and 200 healthy individuals (control group) who underwent medical examinations in health promotion programs during the same period. INTERVENTIONS: All individuals received the diagnostic scrutiny including endoscopic and radiological examinations at initial staging and at follow-up. Individuals suspected of having SPC or NDC underwent histological confirmation. MAIN OUTCOMES AND MEASURES: Risk factors of SPC development and cumulative incidence of SPC (or NDC) in each group. RESULTS: The cumulative 2-, 5-, and 10-year rates of SPC were 4.4%, 8.3%, and 12.4%, respectively, and those of NDC were 1.1%, 3.4%, and 10.5%, respectively (P = .29). Except for the thyroid gland, SPC and NDC were located outside the head and neck region. Univariate analysis was unable to identify any variable significantly predictive of SPC or NDC. CONCLUSIONS AND RELEVANCE In the present study, there was no statistical difference in the SPC cumulative incidence between the SGC and control groups, which might result from the possible limitation of a small sample size.