Abstract
PurposeTo compare the long-term outcomes in patients with salivary gland adenoid cystic carcinoma (SGACC) treated with post-operative chemoradiotherapy (POCRT) versus post-operative radiotherapy (PORT).MethodsWe retrospectively reviewed the records of 91 SGACC patients treated with surgery followed by PORT (n = 58) or POCRT (n = 33) between 2000 and 2013. Treatment outcomes between groups were compared using propensity score matching (1:1 nearest neighbor).ResultsThe median radiation dose was 66 Gy, and patients were followed up for a median of 71 months. Cisplatin-based concurrent regimens were the most commonly used chemotherapy schedules. In the entire study cohort, patients undergoing POCRT showed a trend toward higher locoregional control (LRC) rates than those treated with PORT alone at both 5 and 8 years (97 and 97 % versus 84 and 79 %, respectively; P = .066). Distant metastases were the most common form of treatment failure and occurred in 31 (34 %) patients (PORT, n = 17; POCRT, n = 14). After propensity score matching (33 pairs), patients receiving POCRT had 5- and 8 year LRC rates of 97 and 97 %, respectively, compared with 79 and 67 % for patients treated with PORT alone (P = .017). The two groups did not differ significantly in terms of distant metastasis-free survival (DMFS), disease-free survival (DFS), and overall survival (OS). However, a significantly better opioid-requiring pain-free survival (ORPFS) was achieved in POCRT group (P = .038). Subgroup analyses revealed that patients with stage III − IV disease (P = .040 and .017), positive surgical margins (P = .011 and .050), or perineural invasion (P = .013 and .035) had significantly higher 5- and 8 year LRC and ORPFS when treated with POCRT, respectively.ConclusionsIn SGACC patients, adding concurrent chemotherapy to PORT may increase LRC and ORPFS rates, particularly in presence of stage III − IV disease, positive surgical margins, or perineural invasion. However, no significant differences in DMFS, DFS, and OS were observed.
Highlights
Despite being the most common form of salivary gland cancer, salivary gland adenoid cystic carcinoma (SGACC) is a rare malignancy which accounts for only 1 % of all head and neck tumors [1, 2]
Patients who were treated with post-operative chemoradiotherapy (POCRT) were characterized by a significantly higher prevalence of positive surgical margins and nodal extracapsular spread (ECS) (P = .022), a significantly longer time interval between surgery and RT (P = .018) and trends toward higher T stage (P = .099), larger tumor size (P = .051) and higher bone invasion rate (P = .066)
Compared with patients who received post-operative radiotherapy (PORT), those treated with POCRT were more likely to receive magnetic resonance imaging (MRI) (P = .044), 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET; P = .039), intensity-modulated radiation therapy (IMRT)/VMAT (P < .001), and having been treated with RT more recently (2010–2013 versus 2005–2009 versus 2000– 2004; P = .001)
Summary
Despite being the most common form of salivary gland cancer, salivary gland adenoid cystic carcinoma (SGACC) is a rare malignancy which accounts for only 1 % of all head and neck tumors [1, 2]. Because of its local invasiveness, post-operative radiotherapy (PORT) is frequently used to increase locoregional control (LRC), in patients bearing adverse prognostic factors, including positive surgical margins, advanced T stage, and perineural invasion (PNI) [3,4,5]. Despite important advances in combination therapies, the 10 year rate of locoregional recurrence continues to remain high (~30 %) [3,4,5]. Several multicenter randomized trials have demonstrated the effectiveness of post-operative chemoradiotherapy (POCRT) in patients with head and neck squamous cell carcinoma (HNSCC) [6,7,8]. Chemotherapy is generally reserved for the treatment of recurrent or metastatic SGACC [9], the clinical usefulness of adding concurrent chemotherapy to PORT remains unclear
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