Adenoid cystic carcinoma. An indolent but aggressive tumour. Part B: treatment and prognosis

The purpose of this review is to analyse the very large number of studies (sometimes contradictory) on adenoid cystic carcinoma (ACC). This second part provides a critical analysis of various treatment described in the literature. Anywhere the primary tumour is located, the most common treatment for ACC is complete surgical resection, with or without post-operative radiotherapy (PORT), while conventional photon and/or electron radiotherapy alone and chemotherapy are commonly used in unresectable or metastatic disease. Fast neutron radiotherapy was used in the past with good local results, but the risk of late effects was high and tended to increase over time. Modern carbon-ion radiotherapy seems to be a valid option in selected cases. The quite universally accepted poor prognostic factors are advanced stage, perineural and intraneural invasion, involved margins, and initial presence or later development of neck metastases. The impact of histologic grade on prognosis is controversial. Owing to the long natural history of ACC, the follow-up for patients must be at least 10 years long.