Clinical Profile and Treatment Outcomes of Metastatic Carcinoma with Unknown Primary: A Single Institution Experience

Background: Cancer of unknown primary origin (CUP) is a heterogeneous group of cancers defined by the presence of metastatic disease with no identified primary. CUP has been reported to comprise approximately 2% to 5% of all cancer cases. With the availability of sophisticated imaging techniques and targeted therapies in the treatment of cancer, the extent of workup in CUP remains a challenge and should be based on the clinical presentation, radiological imaging, tumour biomarkers, pathology with immunhistochemistry and the patient’s ability to tolerate therapy. Objectives: To study the incidence, clinical presentation, histology, treatment modalities used, survival and lacunae in not establishing the diagnosis of primary.Materials & Methods: This was a retroprospective study done between January 2014 to December 2018. 650 patients of cancer of unknown primary at presentation were enrolled in this study. After going through various investigations, primary of 387 patients were detected & hence, were excluded from this study. Primary could not be detected in 263 patients even after going through comprehensive work up and henceforth, these were taken up for this study. Demographics, imaging, pathology and treatment data were analyzed from the case records retrospectively between 1st January 2014 to June 2017. The data was collected prospectively between July 2017 to December 2018. Patients with histopathological evidence of metastatic lesion were included and patients whose primary were detected after comprehensive work-up were excluded from this study. Results: Incidence of unknown primary was 0.65 per 1 lakh population. Majority of the patients were from rural areas (77.9%) & most of the patients were in the age group of 61-80 years (47.1%). Male to female ratio was 1.45:1. Abdominal pain (29.7%) and bone pain (20.5%) were the most common clinical symptoms reported. Computed Tomography & PET-CT scans detected primary lesions in 156 out of 650 (24%) & 12 out of 33 (33.3%) patients respectively. Adenocarcinoma was the most common histology (58.6%). The most common treatment modality received by the patients was external beam radiotherapy (12.5%). The median survival of the studied patients was 6-12 months. Conclusion: Patients presenting with metastatic carcinoma with unknown primary have poor outcomes. These patients need a patientcentred, streamlined, rapid diagnostic pathway. The outcome of these patients with standard chemotherapy remains poor. Larger studies with other therapeutic and novel agents are warranted to improve the treatment outcomes.