Treatment Guidelines and Outcome
Surgery is the mainstay of treatment for adenoid cystic carcinoma. Fulfilling the oncologic principle of achieving clear margins is more difficult in this tumor than in other malignant lesions, due to its insidious submucosal and subperiosteal growth as well as to the tendency to spread along named nerves even far from the site of the lesion. Therefore, the surgeon should be aware of the need to check the radical tumor removal with multiple frozen sections and, possibly, to extend the resection to obtain clear margins. This principle is even more relevant in the sinonasal tract, where, for instance, adenoid cystic carcinoma may invade the sphenopalatine fossa and spread intracranially along the maxillary and vidian nerves. Post-operative radiotherapy is commonly indicated, particularly in sinonasal localizations, with the intent to treat residual microscopic disease. A 66 Gy dose is recommended whenever multiple margins are positive or there is extensive soft tissue involvement (Garden et al. 1995).
Overall and disease-free survival of patients with adenoid cystic carcinoma typically declines along the years. In a recent report strictly focused on sinonasal localizations, Wiseman et al. (2002) found a 5-year, 10-year, and 15-year overall survival of 65%, 55%, and 28%, respectively. Interestingly enough, sinonasal primaries have a poorer prognosis when compared with primaries in the major salivary glands and oral cavity/oropharynx (Khan et al. 2001).
Treatment with radiation alone is indicated for unresectable lesions or recurrences. Fast neutron radiotherapy has been shown to give a better local-regional control of the disease than photon beam radiotherapy (Griffin et al. 1988). Encouraging results have been obtained with this technique as a post-operative adjunct even in patients who had undergone only surgical "debulking" (Douglas et al. 2000). However, base of the skull invasion has still a negative impact on both local-regional control and survival (Douglas et al. 2000). Very recently, Schulz-Ertner et al. (2004) have reported a good local-regional control on unfavorable adenoid cystic carcinomas with combined photon and carbon ion radiotherapy.
Adenoid cystic carcinoma is considered a che-moinsensitive tumor, so that chemotherapy is only in very rare instances indicated as a first-line treatment. However, encouraging results in the management of recurrent adenoid cystic carcinoma have been reported by using a combination of vinorelbine and cisplatin (Airoldi et al. 2001).
Unlike other malignant tumors of the head and neck, patients with adenoid cystic carcinoma may survive for years with distant metastases, which can be even resected in carefully selected patients. Therefore, the presence at diagnosis of secondary lesions does not "per se" exclude to treat the primary with a curative intent.
Advanced T stage (Spiro and Huvos 1992; Khan et al. 2001; Mendenhall et al. 2004) and positive margins (Garden et al. 1995; Prokopakis et al. 1999) have been shown to have a negative impact on local control of the disease. More controversial results have been reported instead on histological subtype (Khan et al. 2001) and local microscopic perineural invasion (Vrielinck et al. 1988; Prokopakis et al. 1999). According to Garden et al. (1995) perineural involvement was an adverse prognostic factor only when perineural spread along a major (named) nerve was present.
Considering the natural history of adenoid cystic carcinoma, periodic follow up evaluations, adjusted for stage of the disease and response to treatment, should be extended far longer than the traditional 5-year period.
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