Nasopharyngeal carcinoma (NPC) is a malignancy that arises from epithelial cells of the nasopharynx. It tends to occur in one per 100,000 worldwide and less in Western countries [1,2]. In Saudi Arabia, head and neck cancer cases account for 6 % of all malignancies diagnosed annually, and 33 % of all head and neck cancer cases are nasopharyngeal carcinoma [3]. NPC is classified histologically into 3 types, keratinizing well-differentiated (WHO type I), non-keratinizing well-differentiated (WHO type II), and the commonest type non-keratinizing poorly-differentiated (WHO type III), which has a pathognomonic histological feature, closely associated with Epstein-Barr virus (EBV), with a favorable prognosis [4]. However, because of its proximity, the base of the skull and intracranial extension is a common finding. The nodal involvement has been reported as high as 70 %, regardless of the primary size. And about 30 % of patients develop distant metastases after treatment, with poor prognosis [5].

Identifying failure patterns is crucial to successful treatment, especially when it comes to intensifying locoregional treatments and prescribing systemic therapy [6]. Nevertheless, distant metastasis is the most common treatment failure that affects survival [7,8].

While age was recognized as an important prognostic factor, tumor-related features (TNM stage, EBV status, WHO type) and treatment received (combined chemoradiotherapy, radiation volume dose) was the most important prognostic factors [10]. Therefore, combining chemotherapy and radiotherapy is the primary treatment protocol for advanced disease [11].

This study aimed to examine the patterns of failure and clinical outcomes. Therefore, the findings of this study could be used to identify the nature of the disease after treatment. The study will also demonstrate alarming factors contributing to treatment failure as patients are followed up.