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.