Abstract
BackgroundCancer of unknown primary (CUP) describes patients with metastatic disease without an identified primary tumor site. Successful diagnosis and treatment of these patients remains difficult. Published guidelines on CUP have highlighted “favorable” subtype groups. We investigated a series of CUP patients to review adherence to guidelines, and identification of primary cancers or “favorable” subtypes.MethodsPatients with histologically confirmed CUP at an academic institution from 2012 to 2018 were identified. Patient demographics, tumor presentation, diagnostic work-up and treatment information were retrospectively collected from electronic data records for descriptive analysis and compared to published clinical guidelines. The primary endpoint was the proportion of patients where the primary site was identified. Multivariable logistic regression models were used to identify factors associated with primary site identification. Kaplan-Meier survival curves were used to determine factors associated with poorer OS.ResultsThree hundred and five patients were included with a median follow-up time of 4.3 months. Primary tumor sites were identified in 109 patients (37.5%), which was most commonly lung cancer (33%). Statistical analyses did not identify any demographic or initial presentation factors associated with identifying the primary or not. More diagnostic tests did not increase the likelihood of primary site identification (P=0.44). Patients with an identified primary did not have longer OS than other patients (median 5.2 months vs. 4.7 months, P=0.47). 57 patients (18.7%) who had a defined “favorable” subtype experienced superior OS (36.6 months vs. 3.8 months; P<0.0001). Further, patients with good prognostic status who followed published treatment guidelines had longer OS (17.6 months vs. 13.2 months; P=0.04).ConclusionsCUP remains a difficult cancer to diagnose and treat. These results suggest identifying the primary has less impact than anticipated, but particular efforts to identify patients with “favorable” subtypes of CUP is important prognostically.
Highlights
Cancer of unknown primary site (CUP) describes the diagnosis of a metastatic cancer where the location of the primary tumor is unable to be identified following thorough medical investigation [1]
Median overall survival (OS) times for a patient with a diagnosed primary tumor site in Ontario are significantly longer than CUP patients [9]
Clinical guidelines by several medical organizations are available to reduce the uncertainty in the patient care process by suggesting a list of diagnostic tests; whether Canadian oncologists comply with these guidelines is unknown
Summary
Cancer of unknown primary site (CUP) describes the diagnosis of a metastatic cancer where the location of the primary tumor is unable to be identified following thorough medical investigation [1]. The ultimate aim when investigating CUP remains to try and identify the primary tumor site in order to optimize treatment plans according to other published guidelines. Examples of favorable subtypes include neuroendocrine tumors, isolated axillary nodal metastases in females or non-supraclavicular cervical squamous cell carcinomas. These CUP patients make up 20% of all cases and have well-defined treatment regimens towards dramatically improved survival outcomes [10, 11]. Cancer of unknown primary (CUP) describes patients with metastatic disease without an identified primary tumor site. We investigated a series of CUP patients to review adherence to guidelines, and identification of primary cancers or “favorable” subtypes
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