2018-19 Section 7-Neoplastic and Inflammatory Diseases of the Head and Neck eBook

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CHERAGHLOU ET AL .

benefit is due to cancer-specific survival, although it is unlikely that adjuvant therapy is associated with improved survival from other causes of death. To our knowledge, this is the first large-scale study to investigate the efficacy of adjuvant treatments for salivary gland cancers. Our results support the expanded use of adju- vant radiotherapy for salivary gland cancers that have adverse postoperative features, regardless of pathologic T classification. Additionally, this analysis suggests a more cautious approach to the use of chemotherapy in the adjuvant treatment of salivary gland malignancies. CONFLICT OF INTEREST The authors declare that they have no conflicts of interest with the contents of this article, and all authors had access to the data and a role in writing the manuscript. REFERENCES [1] Speight PM, Barrett AW. Salivary gland tumours. Oral Dis. 2002;8(5):229-240. [2] Bell RB, Dierks EJ, Homer L, Potter BE. Management and out- come of patients with malignant salivary gland tumors. J Oral Maxillofac Surg. 2005;63(7):917-928. [3] Garden AS, Weber RS, Morrison WH, Ang KK, Peters LJ. The influence of positive margins and nerve invasion in adenoid cystic carcinoma of the head and neck treated with surgery and radiation. Int J Radiat Oncol Biol Phys. 1995;32(3):619-626. [4] Copelli C, Bianchi B, Ferrari S, Ferri A, Sesenna E. Malignant tumors of intraoral minor salivary glands. Oral Oncol. 2008;44 (7):658-663. [5] National Comprehensive Cancer Network (NCCN). NCCN Clin- ical Practice Guidelines in Oncology (NCCN Guidelines): Head and Neck Cancers (version I.2016). https://www.nccn.org/profes- sionals/physician_gls/f_guidelines.asp. Accessed June 15, 2016. [6] Terhaard CH, Lubsen H, Van der Tweel I, et al. Salivary gland carcinoma: independent prognostic factors for locoregional con- trol, distant metastases, and overall survival: results of the Dutch Head and Neck Oncology Cooperative Group. Head Neck. 2004; 26(8):681-692; discussion 692-693. [7] Chen AM, Garcia J, Bucci MK, Quivey JM, Eisele DW. The role of postoperative radiation therapy in carcinoma ex pleomor- phic adenoma of the parotid gland. Int J Radiat Oncol Biol Phys. 2007;67(1):138-143. [8] Olsen KD, Lewis JE. Carcinoma ex pleomorphic adenoma: a clinicopathologic review. Head Neck. 2001;23(9):705-712. [9] North CA, Lee DJ, Piantadosi S, Zahurak M, Johns ME. Carci- noma of the major salivary glands treated by surgery or surgery plus postoperative radiotherapy. Int J Radiat Oncol Biol Phys. 1990;18(6):1319-1326. ORCID Shayan Cheraghlou BA http://orcid.org/0000-0003-4382- 7828

malignancies. Our results demonstrate that chemotherapy is typically added to adjuvant treatment for individuals with similar adverse features as those used to determine whether any adjuvant therapy should be administered (higher grade, positive margins, higher N classification, etc). We also found that academic facilities were more likely to use chemother- apy in the adjuvant setting for patients with late-stage disease with adverse features. Although it has been previously reported that academic facilities are more likely to adminis- trate postoperative chemotherapy in other cancers, 53,54 these have been in cases in which the practice has been demon- strated to lead to improved survival. It is unclear why aca- demic facilities have an increased propensity to use chemotherapy in this setting. Finally, patients with govern- ment insurance are less likely to receive chemotherapy in their adjuvant treatment. Although this may be a treatment disparity and a cause for concern in other types of cancer, it is less worrisome given the limited evidence for chemo- therapy ’ s efficacy in the adjuvant therapy of salivary malignancies. There are a number of limitations to this study that should be addressed. First, a number of cases were excluded due to missing data. Although this is a common occurrence with registry data, it limits the power of our analysis and may intro- duce bias. We were also unable to control our analysis for fac- tors, some of which are features that the NCCN guidelines include as indications for adjuvant therapy, such as ECE, peri- neural invasion, lymphatic/vascular invasion, and nodal loca- tion either due to large amounts of missing data or their absence from the data source. Additionally, there is a potential selection bias as it is likely that adjuvant chemotherapy could be used as an additional measure in cases with the most con- cerning adverse features. Another potential selection bias is removal of patients who die during radiotherapy by excluding those who do not receive therapeutic radiation. Among 345 patients who would have otherwise been included in the anal- ysis, 6 were censored and 34 died within 4.75 months of their surgery. Please note that the 4.75 months is the maximum time after surgery that, given a 7-week radiation course, our date restrictions estimate that a patient ’ s radiation treatment would have concluded. Furthermore, we did not have access to patient records detailing the planned treatment modality. However, we addressed this issue by only including patients undergoing a combined treatment modality if the timing of their treatments was consistent with that of adjuvant radiother- apy or adjuvant chemoradiotherapy. The small size of the late-stage without adverse features group also limited the con- clusions that we could make about this group of patients. Finally, we did not have access to data on local control or disease-specific survival. This limits our ability to ascertain whether the survival benefit previously noted for adjuvant therapy in certain cases is driven by improved recurrence rates. We are also unable to conclude that the noted survival

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