Incidence and risk factors of late recurrence in patients with salivary gland cancer

Objectives Recurrence in the late post‐treatment period is relatively common in salivary gland cancer ( SGC ), but risk factors and survival associated with late recurrence have been rarely studied. We investigated the incidence and risk factors of SGC recurrence >5 years after treatment and associated survival. Design A retrospective cohort study. Setting University hospital. Participants A total of 240 patients with previously untreated SGC who underwent definitive treatment. Main outcome measures Late recurrence was defined as recurrence at a time point >5 years after treatment. Univariate and multivariable analyses were used to identify the association of clinicopathologic factors with recurrence‐free survival ( RFS ), cancer‐specific survival ( CSS ) and late recurrence. Results Of the 240 patients, 124 (51.7%) patients developed recurrence during a median follow‐up of 160.0 months (range 121.5–282.2 months). Sixteen (6.7%) patients developed late recurrence; the median time to late recurrence was 92.5 months (range 60.2–138.3 months) after treatment. Multivariable analysis showed that primary site, histologic grade and N classification were independent variables of both RFS and CSS ( P < 0.05 each). Extraparenchymal extension was also an independent variable of CSS ( P = 0.022). In addition, a non‐parotid tumour location was a significant factor for late recurrence in multivariable analysis ( P = 0.017). The median overall survival after the development of late recurrence was 79.7 months (range 0.2–163.4 months), significantly longer than that after early recurrence (19.7 months) ( P = 0.043). Conclusion Late recurrence occurs in some SGC patients. Long‐term close surveillance may be required for patients with non‐parotid SGC .