Pan-tumor treatment, more formally called tissue-agnostic therapy, is a way of choosing a cancer drug based on a specific genetic feature found in the tumor rather than on where in the body the cancer started. A lung cancer patient and a colon cancer patient who share the same molecular abnormality can receive the same drug, because the drug targets the abnormality itself, not the organ. Since the first tissue-agnostic approval in 2017, the concept has gone from a theoretical curiosity to a practical reality affecting roughly one in five cancer patients whose tumors harbor a qualifying genetic marker.
From Organ of Origin to Molecular Target
For most of modern oncology’s history, cancers were named, studied, and treated according to the organ where they arose. Breast cancer got breast cancer drugs, colon cancer got colon cancer drugs, and so on. The logic made sense when the tools for understanding tumors were limited to what a pathologist could see under a microscope. But as genomic sequencing became cheaper and faster, researchers noticed something that reshuffled the picture: some genetic mutations show up across many cancer types, and drugs designed to block those mutations sometimes work regardless of where the tumor sits.
Tissue-agnostic therapies represent a genuine paradigm shift because they change the fundamental way tumors are classified. Instead of asking “where did this cancer start?” the clinician asks “what genetic anomaly is fueling this cancer’s growth?”1PubMed. The evolving landscape of tissue-agnostic therapies in precision oncology The treatment landscape has moved from histology-specific to molecularly defined, targeting alterations regardless of tumor origin.2PubMed Central. Tissue-agnostic biomarkers in solid tumors: current approvals and emerging candidates That single conceptual shift has opened doors for patients whose cancers previously had few or no effective options.
The First Wave of Approvals
The first tissue-agnostic drug approval came in 2017, when the FDA cleared pembrolizumab, an immune checkpoint inhibitor, for any solid tumor that is microsatellite instability-high or has deficient mismatch repair. Those two labels describe essentially the same thing: the tumor’s DNA repair machinery is broken, leaving behind a distinctive trail of errors that makes the cancer more visible to the immune system. Pembrolizumab helps the immune system recognize and attack those tumors, and its approval covered patients with unresectable or metastatic disease no matter which organ the cancer originated in.3PubMed Central. Target-Driven Tissue-Agnostic Drug Approvals-A New Path of Drug Development
The results in practice have been striking. Across 15 different tumor types in the pivotal KEYNOTE trials, pembrolizumab achieved an overall response rate of about 40%, and non-colorectal cancers actually responded at an even higher rate, closer to 46%. Perhaps more meaningfully, responses lasted longer than six months in roughly four out of five patients who responded, with some achieving complete remission.4PubMed Central. Advances in Tissue-Agnostic Targeting in Cancer Therapeutics: Current Approvals, Challenges, and Future Directions For people with rare tumor types that had never been studied in a large clinical trial, those numbers were transformative.
Soon after, two drugs targeting a different genetic feature followed. Larotrectinib and entrectinib both received tissue-agnostic approval for cancers carrying NTRK gene fusions, becoming the second and third drugs approved this way.5PubMed Central. Larotrectinib and Entrectinib: TRK Inhibitors for the Treatment of Pediatric and Adult Patients With NTRK Gene Fusion NTRK fusions happen when part of an NTRK gene accidentally joins with another gene, creating a hybrid protein that drives cancer growth. These fusions are rare overall but appear across a remarkable range of cancers, from pediatric sarcomas to adult thyroid, lung, and salivary gland tumors.
How NTRK Inhibitors Performed Across Tumor Types
Larotrectinib was tested in 55 patients who ranged in age from four months to 76 years and collectively had 17 different tumor types. Three out of four patients responded to the drug, and those responses proved durable: at one year, 71% of responses were still ongoing.6PubMed Central. Efficacy of Larotrectinib in TRK Fusion-Positive Cancers in Adults and Children The fact that the drug worked across such a wide age range and so many cancer types underscored the basic premise of pan-tumor treatment: the mutation matters more than the organ.
Entrectinib, the other NTRK-targeting drug, showed a somewhat lower but still clinically meaningful response rate of 57% across 54 patients with NTRK fusion-positive solid tumors. About 7% had complete responses, and the median duration of response was 10 months. Researchers described the drug as well tolerated with a manageable safety profile.7The Lancet Oncology. Entrectinib in patients with advanced or metastatic solid tumours harbouring NTRK gene fusions (ALKA-372-001, STARTRK-1, and STARTRK-2): an integrated series of three phase 1-2 trials The two drugs are not identical; entrectinib also blocks some other kinase targets and crosses into the brain more readily, which can matter for patients with central nervous system involvement. Having two options also gives clinicians and patients a fallback if one drug causes intolerable side effects.
The Growing List of Qualifying Biomarkers
The concept has expanded beyond those first approvals. Pembrolizumab earned a second tissue-agnostic indication in 2020, this time for tumors with high tumor mutational burden, defined as 10 or more mutations per megabase of DNA. The idea is that tumors carrying many mutations produce more abnormal proteins, which in turn give the immune system more targets to latch onto when a checkpoint inhibitor removes the tumor’s immune shield.8Cancer Cell. What Is Pan-Tumor? A New Approach to Cancer Treatment
Real-world data has generally supported this reasoning, though the strength of the association varies by cancer type. A large pan-tumor study found that patients with high tumor mutational burden had substantially higher response rates to immune checkpoint therapy compared to those with low burden across several tumor types, including gastric cancer, gallbladder cancer, head and neck cancer, and melanoma. Patients with very high mutational burden also lived longer on average than those with low burden.9PubMed Central. High tumor mutational burden predicts favorable response to anti-PD-(L)1 therapy in patients with solid tumor: a real-world pan-tumor analysis That said, the tumor mutational burden biomarker is more contested than the mismatch repair or NTRK biomarkers. Some prospective trials have failed to show clear benefit when selecting patients by mutational burden alone, and critics argue the cutoff of 10 mutations per megabase is somewhat arbitrary.
Other tissue-agnostic targets now include BRAF V600E mutations, RET gene fusions, and HER2-activating mutations. A recent analysis found that when patients with these alterations received matched targeted therapy, response rates were dramatically better than when they received non-matched treatment: about 56% versus 13% overall.10PubMed Central. Clinical outcomes of tumor-agnostic targeting of BRAF, tumor mutation burden-high, and RET On the antibody-drug conjugate front, trastuzumab deruxtecan has shown anti-tumor activity and durable responses across multiple tumor types harboring HER2-activating mutations, with ongoing investigation into broader pan-tumor use.11The Lancet Oncology. Trastuzumab deruxtecan in patients with metastatic solid tumours harbouring HER2 activating mutations (DESTINY-PanTumor02): results from a multicentre, open-label, phase 2 basket trial
How Many Cancer Patients Could Benefit
A natural question is how common these qualifying mutations actually are. A large genomic analysis found that about 21.5% of all tumors harbored at least one tissue-agnostic indication, with 5.4% of those lacking any cancer-specific treatment option. The frequency varies enormously by cancer type, from 0% in pituitary carcinoma to 87% in basal cell skin cancer. Among patients who had at least one qualifying alteration, most (17%) had a single one, about 3% had two, and 1% had three or more.12Nature Communications. Real-world evidence provides clinical insights into tissue-agnostic therapeutic approvals Those numbers suggest that tissue-agnostic therapy is not a niche concept for a handful of patients. It is relevant to a sizeable share of people with cancer, particularly those whose tumors do not fit neatly into an organ-specific treatment pathway.
A separate study looking at an Asian population using a combined DNA and RNA sequencing assay detected at least one tissue-agnostic biomarker in 26 of 29 cancer types examined, covering about 8.4% of samples. Thyroid cancers (30%), melanomas (23%), and lung cancers (17%) were among the most frequently flagged.13npj precision oncology. High clinical actionability of a pan-cancer tissue-based combined DNA and RNA next generation sequencing assay in a diverse Asian population The variation between studies likely reflects differences in the populations tested and the panels used, but the overall message is consistent: these biomarkers show up across a wide spectrum of cancers.
Finding the Mutations That Matter
None of this works without the ability to test tumors for the right genetic features. The workhorse technology is next-generation sequencing, which reads large stretches of a tumor’s DNA in a single run and can simultaneously check for many alterations at once. This is a big advantage over older methods that tested one gene at a time, since tissue-agnostic treatment depends on catching mutations that a clinician might not think to look for in a given cancer type.
For microsatellite instability, a validated sequencing method has shown 97% agreement with traditional PCR and immunohistochemistry testing, which means the same sequencing panel that checks for NTRK fusions or BRAF mutations can also flag mismatch repair problems in the same run.14PubMed Central. A Novel Next-Generation Sequencing Approach to Detecting Microsatellite Instability and Pan-Tumor Characterization of 1000 Microsatellite Instability-High Cases in 67,000 Patient Samples That efficiency matters especially for cancers where microsatellite instability is rare, because in those types no one would ordinarily think to order a separate standalone test for it. Comprehensive genomic profiling can also measure tumor mutational burden and detect other clinically relevant variants in a single assay, identifying actionable targets for essentially all patients tested.15PubMed Central. Use of an Integrated Pan-Cancer Oncology Enrichment Next-Generation Sequencing Assay to Measure Tumour Mutational Burden and Detect Clinically Actionable Variants
Liquid biopsy, which analyzes tumor DNA shed into the bloodstream, is adding another layer. In a study of over 10,000 patients in China, circulating tumor DNA was detected in about 74% of plasma samples, with especially high detection rates in small cell lung cancer and prostate cancer. Among all samples, roughly 41% harbored at least one potential drug-sensitive target.16Nature Communications. Pan-cancer circulating tumor DNA detection in over 10,000 Chinese patients Liquid biopsy has obvious practical appeal: it requires a blood draw rather than a surgical biopsy, it can be repeated over time to track how the tumor is evolving, and it can capture genetic diversity from multiple tumor sites at once. It is not yet a full replacement for tissue-based testing in most situations, but it is increasingly used alongside it.
When the Approach Falls Short
The pan-tumor concept is elegant, but biology is messier than any single framework. Even when a tumor carries the “right” mutation, the tissue it arose from can influence how well the drug works. Researchers have noted that tissue-agnostic drug development can be complicated by tumor-specific resistance mechanisms or other local factors that alter a drug’s effect.17Annual Review of Cancer Biology. Development of Tissue-Agnostic Treatments for Patients with Cancer A brain tumor and a thyroid tumor might both carry an NTRK fusion, but the surrounding tissue environment, the blood supply, and the other genetic mutations present in each tumor can all change the equation.
Acquired resistance is another significant challenge. With NTRK inhibitors, for example, prolonged treatment often leads to mutations in the TRK kinase domain that allow the cancer to escape the drug’s effect. Genomic co-alterations occur frequently alongside NTRK fusions, and it remains unclear whether targeting those additional changes can slow resistance down.18PubMed Central. Analysis of NTRK Alterations in Pan-Cancer Adult and Pediatric Malignancies: Implications for NTRK-Targeted Therapeutics Second-generation TRK inhibitors are in development to address some of these resistance mutations. One compound, ICP-723, has shown the ability to overcome certain solvent front mutations that commonly arise after first-generation TRK inhibitor treatment, though it has reduced activity against other mutation types such as gatekeeper mutations.19Cancer Research. Abstract 6187: ICP-723 is a potent pan-TRK Inhibitor with robust anti-tumor activities against wild-type and acquired drug-resistant mutations of NTRK fusions The resistance landscape is complex enough that a single next-generation drug is unlikely to solve all of it.
How Basket Trials Changed the Evidence Game
Testing a drug across many cancer types at once required a new kind of clinical trial. Traditional trials enroll patients with one cancer type and compare a new drug to a standard treatment. Tissue-agnostic drugs, by definition, need patients with many different cancers who share a molecular feature. The solution has been the basket trial, a study design where multiple tumor types are grouped into “baskets” based on a shared biomarker, and the drug is tested across all of them simultaneously.20PubMed Central. Basket Trials: Review of Current Practice and Innovations for Future Trials
Basket trials are efficient, but they also pose challenges. Some baskets may have very few patients because the biomarker is rare in that tumor type, making it hard to draw firm conclusions. And if a drug works brilliantly in four of seven baskets and flops in three, the question of whether it “works” in a tissue-agnostic sense becomes genuinely difficult to answer. Regulatory agencies have generally handled this by granting accelerated approvals based on response rates and requiring confirmatory data later, which means some tissue-agnostic approvals sit on a less sturdy evidence base than traditional approvals do.
Who Gets Tested and Who Does Not
A tissue-agnostic drug only helps if the patient’s tumor gets sequenced in the first place, and access to genomic testing is uneven. A study examining trends in next-generation sequencing use among cancer patients in the United States found that patients with lower socioeconomic status waited significantly longer to receive sequencing. Hispanic patients and those covered by Medicare or other government insurance programs also faced longer waits. Patients treated at academic medical centers, perhaps counterintuitively, also experienced delays, likely reflecting the complexity of coordinating testing at large institutions.21JAMA Network Open. Trends and Disparities in the Use of Next-Generation Sequencing in Patients With Cancer in the United States
Even once testing is done and a relevant mutation is found, follow-through can be inconsistent. Among patients who tested positive for disease-causing genetic variants in a pan-cancer study, non-White patients had lower rates of receiving genetic counseling compared to non-Hispanic White patients. Black patients in particular had a 40% lower chance of getting counseling after adjusting for other factors.22PubMed Central. Disparities in cancer genetics care by race/ethnicity among pan-cancer patients with pathogenic germline variants These gaps mean that the promise of tissue-agnostic treatment is not yet reaching all the patients who might benefit, and the people being left out are disproportionately those who already face greater barriers to care.
What Rare Cancers Stand to Gain
Tissue-agnostic therapy may have its greatest practical impact for patients with rare and ultra-rare cancers. Running a traditional clinical trial for a cancer that affects a few hundred people a year is logistically nearly impossible: you cannot enroll enough patients at enough sites to generate meaningful data in a reasonable timeframe. Tissue-agnostic drugs sidestep this problem. Because the drug is approved based on the mutation rather than the cancer type, a patient with a rare sarcoma carrying an NTRK fusion can receive the same drug that was studied primarily in more common cancers.
Tumor-agnostic approvals for drugs targeting BRAF, NTRK, and RET alterations, as well as immunotherapy for mismatch repair-deficient cancers, highlight how personalized treatments can reach across diverse cancer types and across the age spectrum.23American Society of Clinical Oncology Educational Book. Designing Clinical Trials for Patients With Rare Cancers: Connecting the Zebras For many patients with rare cancers, a tissue-agnostic approval represents the first time any targeted therapy has been available to them at all. The alternative would be off-label use of a drug approved for a different cancer, which is harder to get covered by insurance and carries less supporting evidence.
Artificial Intelligence and the Next Generation of Biomarkers
The current set of tissue-agnostic biomarkers was identified through traditional molecular biology research. The next wave may arrive faster with help from computational tools. One line of work is trying to predict molecular biomarkers directly from standard pathology images using deep learning. A systematic study across cancer types found that half of the models achieved moderate or better accuracy, and the top-performing models were quite strong, suggesting that routine tissue slides could one day flag patients who need full genomic profiling.24Communications Medicine. A systematic pan-cancer study on deep learning-based prediction of multi-omic biomarkers from routine pathology images If this technology matures, it could dramatically reduce the cost and turnaround time for identifying candidates for tissue-agnostic therapy, especially in settings where comprehensive genomic sequencing is not readily available.
Researchers are also using AI to mine vast quantities of existing literature and multi-omic data for new pan-cancer biomarkers. One group used a framework combining literature mining of 180,000 published articles with multi-omic analysis and clinical validation to identify macrophage migration inhibitory factor as a potential blood-based biomarker for pan-cancer detection, finding it consistently elevated across 21 cancer types at the gene expression level.25PubMed Central. Artificial Intelligence-Driven Multiomics and Clinical Investigation Identify Macrophage Migration Inhibitory Factor as a Pan-Cancer Biomarker Another group developed a deep learning model integrating mutation, methylation, gene expression, and metabolomic data from over 900 pan-cancer cell lines to predict drug responses and identify candidate biomarkers for future study.26Recent Patents on Anti-Cancer Drug Discovery. Attention-enhanced Multi-omics Model for Pan-cancer Drug Response Prediction and Biomarker Discovery These approaches are still early-stage, but they reflect a broader trend: the tools for discovering which patients will benefit from which drugs are becoming faster and more sophisticated, and the tissue-agnostic framework gives those discoveries a direct path to clinical use.