Outcomes and prognostic factors for major salivary gland carcinoma following postoperative radiotherapy
Highlights
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PORT with 3D-CRT/IMRT for salivary gland carcinoma achieved excellent outcomes.
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DM was the most frequent cause of treatment failure and cancer-related mortality.
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Prognostic factors were stage III–IVB, LVI, R1 and high risk pathology.
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Further research is required to determine the incremental benefit of chemotherapy.
Introduction
Major salivary gland carcinomas (SGC) represent <5% of all head and neck cancers. These tumors are not only rare but also very heterogeneous, with over 20 histological subtypes with varying prognoses. The mainstay treatment of SGC is surgical resection. In well-selected patients with early-stage, low-risk disease and R0 resections, surgery alone is appropriate. In all other cases, combined modality treatment is recommended [1].
A number of studies have indicated that postoperative radiotherapy (PORT) significantly improved locoregional control (LRC) [2], [3], [4] and survival [5], [6], [7] in SGC patients with adverse pathologic features. However, despite bimodality therapy for aggressive disease, locoregional failure (LRF), distant metastases (DM) and poor survival have been frequently reported for certain prognostic features such as stage III/IV, lymphovascular invasion (LVI), positive surgical margins and high risk pathology [3], [4], [8], [9], [10], [11], [12]. The recognition of these adverse prognostic factors suggests a role for intensifying therapy in this group of patients.
In our institution, intensity modulated radiotherapy (IMRT) has become the standard of care for SGC in the postoperative setting since 2005. The rationale for conducting this study was to retrospectively review patients with major SGC following PORT to describe the clinical outcomes and to identify patients at high risk of DM who might benefit from the addition of chemotherapy or targeted therapy in multimodality management of SGC.
Section snippets
Study population
After institutional research ethics board approval, we identified all patients with previously untreated, pathologically confirmed primary non-metastatic major SGC, treated with curative intent in our institution between 2000 and 2012 with surgery and PORT. Patients younger than 18 years, those with squamous cell carcinoma (SCC) histology and features suggesting nodal spread from an undetected skin primary, and those with minor SGC or patients treated with surgery alone were excluded from this
Patient characteristics
A total of 304 eligible patients with major SGC were identified. The most common primary site was the parotid gland (n = 237; 78%). MEC (n = 56, 18%), ACC (n = 55, 18%), acinic cell (n = 49, 16%) and salivary duct carcinoma (n = 40, 13%) were the most prevalent histologies. High risk pathology was found in 190 patients (64%): ACC (n = 55), salivary duct carcinoma (n = 40), SCC (n = 11), G2/3 adenocarcinoma (n = 15), G2/3 MEC (n = 35), G2/3 carcinoma ex-pleomorphic adenoma (n = 22), and G3 rare histologic subtypes (n =
Discussion
Major SGC constitute rare cancers with diverse histological subtypes. The present study reports our experience in treatment of SGC with surgery and PORT. With this combined modality treatment, we were able to achieve excellent outcomes. Our 5-(10-) year LC, RC, DC, CSS, and OS were 96% (96%), 95% (94%), 80% (77%), 83% (82%) and 78% (75%), respectively; late toxicity was only 3% at both 5 and 10 years. The comparison of our outcomes with those of other institutions is fairly difficult because of
Conclusion
Surgery and PORT with 3D-CRT/IMRT achieved excellent long-term outcomes with low rates of toxicity in SGC. DM was the most frequent cause of treatment failure and cancer-related mortality. Further research is required for patients with stage III–IVB, LVI, positive surgical margins and high risk pathology to determine the incremental benefit of systemic or targeted therapy in multimodality management of SGC.
Conflict of interest
None declared.
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