Expression of the biomarker COX-2 on circulating tumor cells (CTCs) was found to have prognostic value in nasopharyngeal carcinoma (NPC) in relation to poor response to treatment, the risk of relapse and metastasis, and worse survival outcomes, researchers concluded in an article published in Radiotherapy and Oncology.1

CTC count alone can be informative; it provides clinicians with some information about patient tumor burden and treatment response. The authors reasoned that identification of the specific biomarkers on CTCs could provide a fuller picture of patient status and prognosis across this specific type of head and neck cancer.

The prospective analysis included 131 patients with NPC who had received no prior anticancer medications and did not have metastasis at diagnosis. Treatments were assigned based on clinical TNM stage and patient health: stage I patients received radiotherapy alone, stage II patients received radiotherapy alone or platinum-based concurrent radiochemotherapy, and advanced-stage patients (stage III through stage IV) were given concurrent chemoradiotherapy and neoadjuvant or adjuvant chemotherapy. There were 39 patients (29.8%) in stage I or stage II and 92 patients in the stage III or stage IV category. Twenty-five patients received radiotherapy alone, and all of the other patients (106) were administered a combination of radiotherapy and chemotherapy.

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Blood was collected from patients and COX-2 expression was measured by RNA-ISH at baseline and post-treatment, and investigators followed up with patients every 3 months for the first 3 years of the study and biannually thereafter unless there was a notable clinical development that required attention. Only 115 patients were determined to be evaluable for COX-2 expression after treatment, with 107 patients included in final calculations.

At baseline, 87 of 131 (66.4%) of patients were found to be positive for COX-2 expression on CTCs; the percentage of patients expressing the novel biomarker dropped to 53 of 115 (46.1%) after treatment. This drop was expected by researchers, who acknowledged that cancer treatments “could influence biological reaction and cytokine expression in [the] tumor microenvironment,” so the tumor biomarkers may have evolved in response to drug treatment.1

Of 107 patients, it was determined that COX-2 expression on CTCs post-treatment was significantly correlated with an unfavorable treatment response (P = .011) and an increased risk of local-regional relapse (P = .026) and distant metastasis (P = .007). Expression of this biomarker post-treatment was also significantly associated with poorer progression-free survival (P = .012) and overall survival (P = .018). Baseline COX-2 expression was not found to be significantly correlated with prognosis.

The researchers concluded that this liquid biopsy method overcomes the challenges linked to the biopsy of NPC lesions and “provides a reliable ‘bypass biopsy’ method” to assess the biological features of cancer cells.1


  1. Li Y-J, Luo Y, Xiao-Qi X, Li P, Wang F. The prognostic value of COX-2 expression on circulating tumor cells in nasopharyngeal carcinoma: a prospective analysis [published online August 3, 2018]. Radiother Oncol. doi: 10.1016/j.radonc.2018.07.022