Adenoid cystic carcinoma (ACC) is a locally aggressive tumor of salivary gland origin. Little data exist to guide treatment when this tumor extends to involve the structures of the skull base.
Fifty-one patients with a diagnosis of ACC affecting the skull base were identified from a prospective database at MD Anderson Cancer Center (from 1992 to 2010).
Median follow-up for study patients was 6.75 years. The 5- and 10-year overall survival (OS) rates were 78% and 50%, respectively. Sixty-six percent of patients had progression of their disease. The 5- and 10-year progression-free survival (PFS) rates were 46.7% and 21.0%, respectively. Gross-total resection was achieved in 75% of patients, with 49% having microscopically negative margins at the time of first operation. On univariate analysis, resections with microscopically negative margins were associated with a significant OS advantage (20.1 ± 3.3 years) compared with resections that left residual disease, even if microscopic (10.3 ± 1.6 years, p = 0.035). In patients who underwent reoperation, the effect persisted, with improved OS in those with negative margins (21.4 ± 0.0 vs 16.7 ± 4.0 years, p = 0.06). The use of adjuvant radiotherapy was associated with an OS advantage (16.2 ± 2.5 vs 5.5 ± 2.2 years, p = 0.03) at initial diagnosis and improved PFS (7.8 ± 1.0 vs 2.1 ± 0.62 years, p = 0.005), whereas repeat irradiation provided no benefit. The use of adjuvant chemotherapy at diagnosis or at recurrence was not associated with any significant advantage. Multivariate analysis revealed margin-negative resection at initial operation and at recurrence retained OS significance, even after controlling for age, radiation therapy, and T stage.
ACC of the skull base is best treated with a multidisciplinary approach aimed at maximal, safe resection. Adjuvant radiotherapy should be offered, whereas chemotherapy does not confer benefit.