ESTRO 2025 - Abstract Book

S1000

Clinical – Head & neck

ESTRO 2025

1879

Digital Poster A single institution study on patterns of relapse and survival outcomes in head and neck salivary gland carcinomas treated with surgery and IMRT Justin K.W Ng 1 , Edwin C.Y Wong 1 , Jiminy T.C Liu 1 , Jessica L.C Hung 1 , Janet Q.J Du 1 , Michelle Y Li 1 , George C.N Hui 2 1 Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, Hong Kong. 2 Diagnostic Radiology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, Hong Kong Purpose/Objective: To evaluate real world patterns of relapse and survival outcomes of patients treated with surgery and post operative intensity modulated radiotherapy (IMRT) for head and neck salivary gland carcinoma Material/Methods: We retrospectively reviewed outcomes of patients at our institution treated with curative intent for non metastatic head and neck salivary gland carcinomas between January 2011 and July 2024. Surgery consisted of primary resection +/- regional lymphadenectomy (for node positive or high risk node negative patients). Indications for post operative radiotherapy included high grade histology, close/positive margin, perineural invasion (PNI) and stage T3 4 or node positive tumour. RT was delivered with IMRT and concurrent chemotherapy was delivered in selected high risk cases. Local relapse free survival (LRFS), distant relapse free survival (DRFS) and overall survival (OS) was calculated using the Kaplan Meir method. Cox regression was performed to assess predictors for survival outcomes Results: Total 60 patients were analysed. Median follow up was 66 months. 39 cases (65%) were early stage (AJCC 8 th ed. Stage I-II) tumours. 35 (58%) were of high grade histology. Major and minor salivary gland tumours comprised 41 (68.3%) and 19 (31.7%) cases respectively. Concurrent chemoradiotherapy was given in 2 patients (3%). 5-(10-) year LRFS, DRFS and OS were 91.7% (91.7%), 88% (87%), 85% (80%). Locoregional and distant recurrence occurred in 5 (8%) and 9 (15%) patients respectively. Skull base recurrence (SBR) occurred in 3 patients (60% of locoregional recurrences), all located near the foramen ovale. All 3 cases had parotid primary with high grade histology and perineural invasion. Only one patient with SBR survived beyond 5 years. High grade tumour (HR 4.75, p = 0.04), perineural invasion (HR 3.48, p= 0.012), baseline facial nerve involvement (HR 3.87, p = 0.028) and locoregional failure (HR 9.52, p < 0.01) predicted for OS on univariate analysis. Locoregional failure remained the only significant predictor for OS on multivariate analysis (HR 5.33, p = 0.05). Conclusion: Comparable survival outcomes to historical studies 1,2 were achieved in the real world setting using post operative IMRT for salivary gland cancers. Locoregional failures were mostly at the skull base and were associated with inferior OS. Our findings suggest that skull base coverage should be strongly considered in adjuvant radiotherapy planning, especially for those with high grade histology or PNI.

Keywords: Post operative Radiotherapy, Salivary Gland

References: 1. Hosni A, Huang SH, Goldstein D, Xu W, Chan B, Hansen A, et al. Outcomes and prognostic factors for major salivary gland carcinoma following postoperative radiotherapy. Oral Oncol [Internet]. 2015;54:75–80. Available from: http://dx.doi.org/10.1016/j.oraloncology.2015.11.023 2. Mathew MM, Choi M. Postoperative radiation therapy for salivary gland malignancies. Int J Radiat Oncol Biol Phys [Internet]. 2016;94(4):956. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0360301615271477