Cancers of unknown primary: Institut Curie takes on the challenge of treating metastases without knowing the primary tumor

An unknown primary cancer (CUP, also called cancer of unknown origin) is defined by the presence of metastases in a patient, without being able to identify the primary tumor after the usual examinations. Every year, nearly 7,000 new cases are diagnosed in France. Given that these forms of cancer are often diagnosed at an advanced stage, therapeutic management is complex. First-line treatments are based on broad-spectrum empirical chemotherapy, but their effectiveness is very limited, with an overall survival of less than one year for most patients.

For several years, the use of new molecular biology technologies has made it possible to improve the identification of the origin of CUP metastases and thus to propose personalized treatments. However, access to these technologies is very uneven across the national territory, and their use in routine clinical practice requires specific expertise. In this context, a multidisciplinary consultation meeting (RCP) dedicated to unknown primary cancer and coordinated nationally by Institut Curie was created in 2020 with the aim of guiding the diagnostic and therapeutic management of patients and promoting access to advanced diagnostic technologies throughout France.

"With approximately 1,000 patients, the national database of CUPs gathers extremely rich and valuable clinical, pathological, and molecular data for these rare and serious cancers," declares Dr. Sarah Watson, medical oncologist and researcher at Institut Curie, Director of the Early Clinical Trials and Innovation Department at Institut Curie, and also national coordinator of the multidisciplinary consultation meeting dedicated to CUPs. "Our database is growing, our research is accelerating, and today, it allows us to study intermediate cohorts to better understand, better classify CUPs, and propose therapeutic solutions to patients."

Thanks to data from the national multidisciplinary consultation meeting, teams at Institut Curie have managed to identify a specific signature of response to immunotherapy, likely to constitute a predictive biomarker for treatment response and prognostic for disease progression. Furthermore, new data reinforce results showing that the consultation of clinical, pathological, and molecular expertise improves the survival of patients with CUP. Furthermore, Institut Curie has conducted research on patient subgroups, particularly work on 50 adolescents and young adults, which has refined therapeutic solution proposals specifically dedicated to this subpopulation.