Cancer-of-Unknown-Primary-Origin: A SEER-Medicare Study of Patterns of Care and Outcomes among Elderly Patients in Clinical Practice

Abstract

Knowledge of contemporary patterns of cancer-of-unknown-primary-origin (CUP) diagnostic work-up, treatment, and outcomes in routine healthcare is limited. Thus, we examined data from elderly patients diagnosed with CUP in real-world US clinical practice. From the Surveillance, Epidemiology, and End Results-Medicare-linked database, we included patients ≥ 66 years old with CUP diagnosed between 1 January 2013 and 31 December 2015. We analyzed baseline demographics, clinical characteristics, methods of diagnostic work-up (biopsy, immunohistochemistry, imaging), treatment-related factors, and survival. CUP diagnosis was histologically confirmed in 2813/4562 patients (61.7%). Overall, 621/4562 (13.6%) patients received anticancer pharmacotherapy; among these, 97.3% had a histologically confirmed tumor and 83.1% received all three procedures. Among those with a histologically confirmed tumor, increasing age, increasing comorbidity score, not receiving all three diagnostic measures, and having a not-further specified histologic finding of only 'malignant neoplasm' were all negatively associated with receipt of anticancer pharmacotherapy. Median overall survival was 1.2 months for all patients. Median time between CUP diagnosis and treatment initiation was 41 days. Limited diagnostic work-up was common and most patients did not receive anticancer pharmacotherapy. The poor outcomes highlight a substantial unmet need for further research into improving diagnostic work-up and treatment effectiveness in CUP.

Keywords: Medicare Part A; Medicare Part B; SEER program; diagnostic tests and procedures; drug therapy; neoplasms; registries; survival analysis; unknown primary.

Figure 1

Trends in the number of diagnostics^a performed among treated (n = 621; closed circles) and untreated patients (n = 3941; open circles) with CUP. B, biopsy; CUP, cancer-of-unknown-primary-origin; IHC, immunohistochemistry; IM, imaging. ^a Record of claim for a biopsy, immunohistochemistry, or imaging modality (computed tomography, positron emission tomography, magnetic resonance imaging) for any reason.

Figure 2

Survival of patients with CUP who were (A) untreated, overall and by histologic confirmation status, (B) treated without pharmacotherapy, and (C) treated alongside pharmacotherapy. * Suppressed data based on NCI guidelines for confidentiality. CUP, cancer-of-unknown-primary-origin; NCI, National Cancer Institute. See Table S4 for further data on patient survival.