Unravelling the enigma of cancer of unknown primary

Cancer of unknown primary (CUP) is a poorly understood type of cancer where you cannot tell where in the body the cancer started.¹ If a doctor cannot find the original location of a cancer, treatment is limited to chemotherapy.

There is an urgent medical need for better understanding of what drives CUP, to improve therapy options:

Approximately 3-5% of cancers are classified as CUP.1

Not knowing the original location of the cancer can be frustrating for patients and doctors.

Median overall survival is only between eight and twelve months for people diagnosed with CUP.2

It is the fourth most common cause of cancer death.1

In the absence of information about the cancer’s site of origin, it’s important to gather as much molecular information as possible. This includes finding out which mutations are driving the cancer.

This information can be revealed by comprehensive genomic profiling (CGP). 

CGP is a type of genomic testing that can be used to help find specific changes in the DNA of a tumour, or the unique “fingerprint” of a patient’s tumour, to help determine how it behaves and grows.3

From either tumour tissue or blood, CGP uses a testing method called next-generation sequencing to analyse hundreds of genes at once to identify those which drive cancer, and which can inform treatment strategies.4

Insights from CGP can help physicians to identify a targeted therapy, immunotherapy, or clinical trial that is tailored to the patient’s tumour profile, potentially removing the need to determine the cancer’s original location to treat it effectively. It can also inform care in case of no actionable biomarker is identified.

Using CGP to inform the treatment of patients with CUP could pave the way for a truly targeted and personalised treatment strategy.

It could help patients to achieve better outcomes and avoid unnecessary treatments and diagnostic procedures, as well as support healthcare systems to be sustainable over the long term.

CGP is increasingly being incorporated into clinical guidelines; for example, the National Comprehensive Cancer Network clinical guidelines for CUP now recommend CGP to identify actionable genomic alterations.2


  1. Qaseem A, et al. Cancer of unknown primary: a review on clinical guidelines in the development and targeted management of patients with the unknown primary site. Cureus. 2019;2;11(9):e5552. 

  2. NCCN Clinical Practice Guidelines in Oncology: Occult Primary (Version 3.2023).

  3. Thomas DM, et al. Unlocking access to broad molecular profiling: benefits, barriers, and policy solutions. Public Health Genomics. 2022; 25 (3-4): 70–79.

  4. Woodhouse R, et al. Clinical and analytical validation of FoundationOne Liquid CDx, a novel 324-Gene cfDNA-based comprehensive genomic profiling assay for cancers of solid tumor origin. PLoS One. 2020; 25;15(9):e0237802.

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