Luangyot Thongthieang, MD¹

Background: Carcinoma of unknown primary (CUP) remains a heterogeneous disease, with poor survival outcomes and limited data from Thailand.

Objective: To describe clinical characteristics, clinicopathologic features, treatment patterns, progression-free survival (PFS), overall survival (OS), and to identify prognostic factors of patients with CUP.

Materials and Methods: A retrospective study was conducted on patients diagnosed with CUP between January 2012 and December 2022 at Khon Kaen Cancer Center, Khon Kaen Hospital. Patients were categorized into favorable- or unfavorable-risk subsets according to ESMO criteria.

Results: Among 102 patients, the median age was 60.7 years, and 64.7% were male. Disseminated disease was present in 86.3%, and adenocarcinoma (56.86%) was the most common histology, and favorable-risk subsets accounted for 72.5%. The median PFS for the favorable-risk groups and the unfavorable-risk group were 7 months vs. 1 month (p<0.001), respectively. The median OS for favorable-risk groups and unfavorable-risk groups were 17 months vs. 2 months (p<0.001), respectively. Most treated patients received empirical platinum-based chemotherapy, predominantly paclitaxelplatinum combinations. In multivariable analysis, disease extent (localized vs. disseminated) and smoking status (smoke vs. non-smoke) were the only independent prognostic factors for OS and PFS.

Conclusion: This real-world CUP cohort shows patients with favorable risk groups have better survival outcomes than unfavorable risk groups, with survival comparable to specialized international series. Disease extent and smoking status emerged as the only independent prognostic factors.

Received 24 March 2026 | Revised 14 May 2026 | Accepted 21 May 2026

DOI: 10.35755/jmedassocthai.2026.9.04408