Second primaries after major salivary gland cancer.

OBJECTIVES To evaluate the risk of second primary cancers in patients with major salivary gland cancer using a large population database and to examine the effects of sex, salivary gland cancer histology, and radiation therapy on the risk of second primaries. STUDY DESIGN Population-based study using the Surveillance, Epidemiology, and End Result (SEER) cancer database. SUBJECT AND METHODS The subjects were 15,572 men and women ages 15 and above, diagnosed with cancer of the major salivary glands from 1973 to 2006. RESULTS There was an increased risk of oral cavity (standardized incidence ratio [SIR] = 3.48, P < .05), salivary (SIR = 9.97, P < .05), lung and bronchus (SIR = 1.60, P < .05), kidney (SIR = 1.68, P < .05), and thyroid (SIR = 2.66, P < .05) cancers. Men had an increased risk of developing kidney cancer (SIR = 1.70, P < .05) compared with women (SIR = 1.64, P > .05). Patients with mucoepidermoid carcinoma had an increased risk of a second salivary gland cancer (SIR = 8.97, P < .05) and thyroid cancer (SIR = 3.97, P < .05). Patients with adenoid cystic carcinoma had an increased risk of oral cavity (SIR = 3.76, P < .05) and nasopharyngeal (SIR = 16.88, P < .05) cancers. Patients with acinar cell carcinoma had an increased risk of salivary (SIR = 31.36, P < .05), kidney (SIR = 2.98, P < .05), and thyroid (SIR = 3.85, P < .05) cancers. Patients who received radiation therapy had a higher incidence of lung and bronchus (SIR = 2.11, P < .05), laryngeal (SIR = 3.08, P < .05), and thyroid (SIR = 2.95, P < .05) cancers compared with patients who did not receive radiation therapy (SIR = 1.18, 0.48, and 2.39, respectively; P > .05). Patients had an increased risk of developing second primaries, even 10 years after diagnosis of primary salivary gland cancer. CONCLUSIONS Patients with major salivary gland cancers are at a risk for certain second primary cancers. This highlights the need for long-term surveillance in these patients, not only for recurrence but also for second primary cancers.