What is the long-term local control rate of patients with adenoid cystic cancer (ACC) managed by surgery?
Patients with ACC who do not receive postoperative radiation therapy (PORT) have poorer local control.
Explore this issue:October 2017
Background: ACC is a rare tumor of the salivary glands and accounts for only 1% of all head and neck malignancies. It affects people in all decades of life and has no known risk factors. Histologically, there are three main growth patterns: solid, cribriform, and tubular patterns. Solid ACC has been reported to show a more aggressive biological behavior.
Surgery with PORT forms the cornerstone of treatment. ACC has a predilection for perineural invasion, which may increase the risk for local recurrence. Other factors associated with local failure include advanced tumor (T) stage and the presence of positive margins. These factors are considered indications for postoperative radiation, although perineural invasion as an isolated factor is controversial if no named nerves are involved.
Study design: Single-institution retrospective cohort study.
Setting: Memorial Sloan Kettering Cancer Center, New York City.
Synopsis: Researchers identified 87 patients who had received surgery for ACC between 1985 and 2009. Patient, tumor, and treatment characteristics were recorded. Local recurrence-free survival (LRFS) was recorded by the Kaplan-Meier method. Predictors of local control were identified.
The study group median age was 54 years. Seventy-two (83%) patients had perineural invasion, 61 (70%) had close/positive margins, and 58 (67%) had pT 1T2. Fifty-nine (68%) patients had postoperative radiation therapy (PORT). With a median follow-up of 85 months, the 10-year LRFS was 78.7%. There were 14 local recurrences. On multivariable analysis, pathological tumor (T)3T4 stage and no PORT were independent predictors for local failure. Patients with no PORT had a 13-fold increased risk of local failure compared with patients treated with PORT after adjusting for stage.
Study limitations include that it was retrospective and that there as considerable heterogeneity in the patient group. The authors recommend that extrapolation of the data to the use of PORT in patients with early T-stage tumors without adverse features needs should be done with caution. Further, they indicate that their data require substantiation with data from other large series, and note that, despite the fact that a randomized control trial would be the obvious gold standard to decide whether PORT is efficacious in all patients, it is extremely unlikely that such a study could be successfully carried out due to the rarity of this tumor.