Why is tumor tissue so important in the management of cancer patients? It turns out it goes well beyond establishing a diagnosis.
The purpose of obtaining tissue from a tumor through a biopsy has evolved over the last few years from merely establishing a diagnosis to predicting response to therapy and providing a realistic prognosis for patients. This evolution stems from the recently acquired ability to precisely analyze tissue using molecular assays, biomarkers and genotyping and is in keeping with the notion of “molecular medicine” itself often referred to as “personalized or precision medicine” where a treatment plan is formulated based on the specific characteristics of a patient’s tumor. Indeed, patients and physicians alike want to know the status of a tumor from a molecular point of view in order to identify potential targets within this tumor for drug therapy and suggest available drug options. In this manner, a “personalized” treatment plan can be formulated based on realistic expectations, making the need for tissue in the first place absolutely critical.
Cancer is not a static process which means that tissues samples are required throughout the lifetime of the tumor; from the initial diagnosis until the tumor is entirely destroyed. Obtaining samples at multiple time points has now become an essential component of the management of cancer patients to monitor the evolution of a specific tumor and assess real-time the molecular signature of a tumor. In addition, tumors are notoriously heterogeneous not only across sites of metastases but also within a single tumor making it very difficult to obtain a global picture of the tumor from its molecular characteristics. Therefore, multiple samples in various locations are often necessary for molecular profiling, help select a treatment option and assess tumor resistance. Fortunately, constant progress made in imaging technology allows for extremely precise visualization of tumors, targeting and sample collection. A tumor can now be sampled at its core, rim or anywhere in between. Such percutaneously obtained tumor samples have become standard of care for cancer patients.
Identifying mutations that can be targeted with drugs is key to being able to provide a treatment plan for patients, especially in view of the recent shift away from conventional chemotherapy to the newer targeted drugs capable of inhibiting specific pathways that are unregulated or simply “present” in cancer cells (EGFR, ALK, VEGF, BRCA and more recently PD-1, PD-L1 and CTLA-4 to name a few). Genomic profiling has also become indispensable in the conduct of clinical trials where the identification of specific biomarkers is often required before a patient can be enrolled in a study. Such predictive biomarkers can also streamline drug development by allowing to design smaller clinical trials focused on treating tumors that have a common biologic signature. Such an approach could possibly do away with the large clinical trials typical of an old era where the anatomic location of a tumor was more important than its biologically-based targets.
We have come a long way since a needle was inserted into a tumor to obtain a diagnosis. From diagnosis to molecular profiling, tumor resistance and biomarkers of response, the need for tumor tissue in the management of cancer patients has become absolutely indispensable. As a result, the role of imaging to guide such biopsy procedures will only grow since precision to obtain tumor samples is paramount. In the end, cancer patients will be better served and the era of “personalized medicine” will truly be here to stay.