THE INFLUENCE OF POSITIVE MARGINS AND NERVE INVASION IN ADENOID CYSTIC CARCINOMA OF THE HEAD AND NECK TREATED WITH SURGERY AND RADIATION

Purpose: Surgery is the primary treatment for adenoid cystic carcinoma s arising from major and minor salivary glands of the head and neck. H owever, local recurrence is frequent because of the infiltrative growt h pattern and perineural spread associated with these tumors. At UTMDA CC, we have had a long-standing policy of using postoperative radiothe rapy to reduce the risk of local recurrence and to avoid the need for radical surgery; this 30-year retrospective study analyzes the results of this combined modality approach. Methods and Materials: Between 19 62 and 1991, 198 patients ages 13-82 years, with adenoid cystic carcin omas of the head and neck, received postoperative radiotherapy for kno wn or suspected microscopic residual disease following surgery. Distri bution of primary sites was: parotid: 30 patients; submandibular/subli ngual: 41 patients; lacrimal: 5 patients; and minor Salivary glands: 1 22 patients. Eighty-three patients (42%) had microscopic positive marg ins and an additional 55 (28%) had close (less than or equal to 5 mm) or uncertain margins. One hundred thirty-six patients (69%) had perine ural spread with invasion of a major (named) nerve in 55 patients (28% ). Using radiation techniques appropriate to the primary site, a media n dose of 60 Gy (range 50-69 Gy) was delivered to the tumor bed. Follo w-up ranged from 5-341 months (median, 93 months). All surviving patie nts had a minimum of 2 years follow-up. Results: Twenty-three patients (12%) had local recurrences with 5-, 10-, and 15-year actuarial local control rates of 95%, 86%, and 79%, respectively. Fifteen of the 83 p atients (18%) with positive margins developed local recurrences, compa red to 5 of 55 patients (9%) with close or uncertain margins, and 3 of 60 patients (5%) with negative margins (p = 0.02). Patients with and without a major (named) nerve involved had crude failure rates of 18% (10 out of 55) and 9% (13 out of 143), respectively (p = 0.02). There was a trend toward better local control with increasing dose. This was significant in patients with positive margins, in whom crude control rates were 40 and 88% for doses of <56 Gy and greater than or equal to 56 Gy, respectively (p = 0.006). Actuarial 5-, 10-, and 15-year freed om from relapse rates were 68%, 52%, and 45%, respectively. Base of sk ull and neck failures were uncommon with or without elective treatment , developing in 2 and 3% of patients, respectively. Distant metastases were the most common type of disease recurrence, developing in 74 pat ients (37%) of whom 62 (31%) were disease-free at the primary site. Co nclusions: Excellent local control rates were obtained in this populat ion using surgery and postoperative radiotherapy and we recommend this combined approach for most patients with adenoid cystic carcinomas of the head and neck. Perineural invasion was an adverse prognostic fact or only when a major (named) nerve was involved. Microscopic positive margins was also an adverse prognostic factor, but even when present, local control was achieved in over 80% of our patients. We recommend a dose of 60 Gy to the tumor bed, supplemented to 66 Gy for patients wi th positive margins. Despite effective local therapy, one-third of pat ients fail systemically, and good treatment to address this problem is lacking.