Biomarkers are not validated or standardised
Tests that decide who gets a drug are often not validated prospectively and are measured differently in every lab.
Modern oncology allocates drugs by biomarker, but the biomarkers are held to a lower standard than the drugs. PD-L1 is scored with several non-interchangeable antibodies and cut-offs; HER2-low, which now defines eligibility for trastuzumab deruxtecan, depends on distinguishing IHC 0 from 1+, where pathologist agreement is poor; TMB varies by panel, bioinformatic pipeline and tumour type; HRD assays disagree with each other; and TROP2 and other ADC targets are given without any validated assay at all. Most biomarkers are validated retrospectively within the pivotal trial of one drug, on one assay, then used with different assays in practice. The consequences are patients wrongly included or excluded, irreproducible subgroup results, and combination biomarkers that never reach the clinic. Analytical standardisation, external quality assurance, prospective biomarker-stratified trials, and AI quantification that removes inter-observer variability are the remedies.
- Each drug sponsor develops its own companion assay and cut-off, with no obligation to harmonise.
- Immunohistochemistry is semi-quantitative and subject to pre-analytical variation and inter-observer disagreement.
- Retrospective validation within a single trial is accepted by regulators as sufficient.
- External quality assurance schemes are voluntary in many countries.
- Reimbursement for testing lags approval, so laboratories adopt cheaper, non-validated substitutes.
- The Blueprint PD-L1 IHC Assay Comparison Project and Friends of Cancer Research TMB Harmonization Project align assays across vendors.
- The ASCO-CAP HER2 guideline update (2023) added HER2-low reporting standards, and AI-assisted HER2 scoring is being validated to reduce inter-observer variability.
- NordiQC and UK NEQAS run external quality assessment for immunohistochemistry and molecular pathology.
- The EU In Vitro Diagnostic Regulation (IVDR) raises evidence requirements for companion diagnostics.
- FoundationOne CDx and other pan-tumour companion diagnostics consolidate multiple biomarkers on one validated platform.
- TROP2 PET and other quantitative imaging biomarkers are being developed as alternatives to tissue IHC for ADC target selection.
A Japanese trial found vitamin D supplements did not help everyone after digestive cancer surgery, but appeared to help a subgroup identified by a tumour marker. That subgroup deserves its own trial.
Before cancer spreads, distant organs are changed to become welcoming. A test for those changes would show which organ is at risk while a person still looks cancer-free.
Volatile compounds in breath differ in cancer. A breath test validated in truly symptomatic patients, not lab volunteers, could tell GPs who needs urgent scans and who can safely wait.
Blood and tissue samples collected in cancer trials are the best material for validating new tests, but most sit unused under contracts that make access impossible. A commons would make them available for approved research.
Completed trials have stored samples. Testing a new biomarker on them with the plan written in advance is nearly as good as a new trial and far cheaper, but regulators have no clear route to accept it.
Tests for 'HRD', which decide who gets PARP inhibitors, rely on genomic scars that reflect the tumour's past, not its present. A test of current DNA-repair function would be better, but needs standardising.
Thousands of tests that could predict who benefits from a treatment are published and never validated. A fund would pay for the boring but essential confirmation studies in independent patient groups.
Thousands of cancer biomarkers are published; almost none reach patients because nobody validates them fairly. Create a public service that tests any candidate blind against stored samples.
Targeted cancer drugs often reach a country years before the test needed to select patients is approved there. Recognising other regulators' test approvals would close the gap.
Between diagnosis and surgery there are usually a few weeks. Giving a new drug in that window and comparing the tumour before and after surgery shows whether it hits its target in real people, quickly and cheaply.
Tumour mutational burden decides who gets immunotherapy in some settings, but every sequencing panel calculates it differently. A shared calibration would make the number mean the same thing everywhere.
Some tumours change fast and escape drugs quickly; others are stable. A single validated score for how evolvable a tumour is would tell doctors how aggressively to combine treatments.
Two people can have identical treatment and only one develops heart failure or a second cancer years later. Collecting blood and genetic data from survivors could reveal who is at risk and who can be reassured.
Some people have only a few spots of spread and can be cured by treating each one. Others have many spots not yet visible. A test to tell them apart would spare futile treatment and find curable patients.
Once a year, send the same blinded blood samples to every company selling a tumour-DNA test and publish how each performed.
Trials often measure a stand-in for survival, such as time until the cancer grows on scans. An independent body would test, for each cancer and treatment type, whether the stand-in actually predicts survival, and publish the answer.
Whether a breast cancer counts as 'HER2-low', and so qualifies for a powerful drug, depends on which lab reads the slide. Standard reference slides with known HER2 levels would make the answer consistent.
Dozens of companies sell blood tests for tumour DNA and they report different results on the same sample. Government-issued reference samples with known amounts of tumour DNA would expose the differences.
Some tumours have broken the machinery that displays their identity to immune cells. Those patients cannot benefit from most immunotherapy and should be routed elsewhere.
Cancer cells travelling in the blood can be counted. If a drug clears them, that is an early sign it may stop spread, and it reads out in weeks rather than years.
A drug label says 'for PD-L1 positive patients' but does not say that other tests give different answers. Labels should list the validated tests and how much they disagree.
If a blood test reliably shows whether cancer will come back after surgery, trials could use it instead of waiting years for relapse. Regulators have a process to bless such a test; oncology should use it.
Lab-grown mini-tumours are already being sold to guide treatment, but the tests are not validated like other medical tests. They should be.
Drugs are described as phase 1, 2 or 3 so everyone knows how proven they are. Biomarkers should carry the same kind of label so a 'promising' marker is not mistaken for a validated one.
A drug aimed at a mutation present in every tumour cell works differently from one aimed at a mutation in only some cells. Test reports should say which is which.
The detailed molecular maps of tumours being built today mostly lack information on what happened to the patient. Require every atlas sample to carry consented outcome data.
Companies sometimes choose the biomarker threshold that makes their trial look best after seeing the data. Requiring the threshold to be fixed and published before the big trial starts prevents this.
When a screening test misses a cancer, we should know. Linking every negative result to the cancer registry and publishing what was missed, by stage, should be a condition of use.
The support cells that build a tumour's scaffolding come in several types: some protect the tumour, others restrain it. Treating all of them the same way explains past failures.
Screening finds cancers that would never have caused harm alongside dangerous ones. Pair every screening test with a test that says which is which, so people with harmless findings can safely watch and wait.
If one lab suddenly starts finding twice as many 'positive' results as others, something has gone wrong with its test. Pooling positivity rates across labs would catch this automatically.
Thousands of papers extract 'radiomic' features from scans to predict outcomes, but the features change with scanner settings. Journals should require standard compliance before any clinical claim is made.
There are several different PD-L1 tests, each tied to a different drug, and they disagree. A single digitally calibrated scale would let any lab's result be translated into any drug's cut-off.
Many patients with advanced lung or bowel cancer start treatment without the gene tests that would show whether a targeted drug would work. Let the pathologist order the full test the moment cancer is confirmed, without waiting for an oncologist.
Insurers pay for many cancer tests that have never been shown to improve outcomes. Paying only inside studies that measure whether the test helps would sort the useful from the useless.
Drug trials must be registered before they start so results cannot be hidden or reshaped. Studies that claim a biomarker predicts outcome should be registered too.
Anyone building a new test for HER2, PD-L1 or tumour DNA should be able to check it against the same public reference set. Today each developer validates on private data nobody can inspect.
Labs already get tested on whether they score biomarkers correctly, but the results are private. Publishing them would let hospitals and patients avoid labs that get it wrong.
Trials often have independent radiologists check whether tumours grew. How often they disagree with the treating doctors is a measure of how trustworthy the result is, and it is rarely published.
Current blood tests miss leftover cancer in many patients. Reading thousands of mutations at once, rather than a few dozen, can detect far smaller amounts.
PSMA scans could measure prostate cancer burden and response far better than PSA, but no one has done the standardisation work to make the measurement trustworthy across scanners.
Many patients are denied a drug because a test says they will not benefit. For the most important tests, that assumption should itself be tested in a trial.
Fluid taken from the lower back contains DNA from brain tumours. Testing it can diagnose, monitor and detect resistance without brain surgery.
How a tissue sample is handled before it reaches the lab changes the results of biomarker tests. That handling time is almost never recorded, so nobody can tell a true negative from a spoiled sample.
Different companies' leftover-cancer blood tests disagree, and there is no shared yardstick. Public reference samples would let anyone check which test actually works.
A test approved to select patients for a drug in the US must go through separate approval in Europe, Japan and elsewhere, delaying the drug. Accepting each other's test approvals would fix the delay.
Trials that fail still collected thousands of blood and tissue samples. Instead of being destroyed, they should be pooled so scientists can learn who might have benefited.
Instead of testing a drug in lab models first and hoping the results carry over, build the same models from trial participants and run both experiments in parallel to see how well the models predict.
Wasting has several causes. Measuring the specific hormone in each patient's blood would put the right patients into the right trial instead of mixing everyone together.
Growing a patient's own tumour-fighting cells only works if those cells are there to start with. A test for them would spare futile treatment.
New microscopes can measure dozens of proteins at once and map where immune cells sit in a tumour. These readouts could predict immunotherapy response, but every lab does it differently.
For each cancer type, agree the set of stains and tests that are always needed, and have the lab run them automatically on diagnosis rather than waiting for someone to ask.
Cancers driven by MYC need to make proteins at an unusually fast rate. Slowing the cell's protein factory hits them harder than it hits normal cells.
Cancer cells enter the blood mostly during rest, so a morning blood test may miss them. Sampling and dosing at the right hour may be a free improvement.
For very rare cancers there is often no genetic clue and no trial. Growing the patient's cells and testing drugs on them directly can suggest what to try.
Many people get a genetic result of uncertain significance, which cannot be acted on. Lab methods now let us test every possible variant in a gene in advance.
Trials that only enrol patients with a positive biomarker can never prove the biomarker matters. Including a smaller biomarker-negative group would show whether the test is really needed.
Whether immune cells are next to cancer cells matters more than how many there are. Turning that spatial picture into a reliable, standardised test would predict response better.
Tumours starved of oxygen produce a chemical that switches immune cells off. A scan can show which tumours are starved, and those are the ones to treat with blockers.
A single protein predicts whether a tumour will respond to DNA-damaging drug payloads. Measuring it could stop patients receiving a second drug of the same kind that will not work.
Pragmatic trials want to use the progression dates recorded in ordinary clinic notes instead of expensive protocol scans. Checking how well those routine records match formal trial measurements would show when that shortcut is safe.
AI is starting to decide which patients get which cancer drug. Every change to the software should be tested against a fixed public set of cases before it is used on patients.
When immunotherapy works, specific immune cell families multiply in the blood within weeks. Tracking that could tell patients early whether to continue.
For patients with advanced melanoma, immunotherapy offers a realistic chance of long-term survival and probably cure, and the ten-year data show that patients who are alive and progression-free at three years rarely die of melanoma afterwards. Nivolumab plus ipilimumab gives the best long-term results but at a high price in serious side effects; nivolumab alone or nivolumab plus relatlimab are alternatives for patients at lower risk or with autoimmune concerns. The trial is also a caution about surrogate endpoints: the survival plateau took years to become visible.
After bladder removal, a blood test can now tell who needs immunotherapy and who can safely be spared it. This is the model for MRD-guided adjuvant therapy across cancers: treat the blood-positive, watch the blood-negative.
Patients with hormone-receptor-positive metastatic breast cancer that has stopped responding to endocrine therapy can be offered trastuzumab deruxtecan as their first chemotherapy-type treatment if the tumour shows any HER2 staining, rather than waiting until after conventional chemotherapy. Whether to use it before or after chemotherapy is now a choice, since overall survival was not shown to differ and the drug carries a risk of lung inflammation.
For hormone-receptor-positive metastatic breast cancer that has already had chemotherapy, Dato-DXd controls the disease for longer with fewer severe side effects than chemotherapy, but does not help patients live longer, so it is not a standard option here. The result is a reminder that progression-free survival is a surrogate; regulators and clinicians should wait for survival data before adopting an ADC in a setting where later therapies are effective.
The blood test stratifies risk far better than stage or pathology. It supports treating ctDNA-positive patients and suggests ctDNA-negative patients gain little from chemotherapy, but because treatment was not randomised the de-escalation claim needs the randomised trials that are now under way.
A multi-cancer blood test can be run in ordinary clinics, and most positive results can be resolved with imaging. But six in ten positives are false alarms that take months to resolve, and the test misses most cancers. Whether it reduces late-stage cancer or deaths is unknown; that requires randomised trials.
Women with newly diagnosed advanced or recurrent endometrial cancer should receive a PD-1 antibody (dostarlimab or pembrolizumab) with their chemotherapy, and mismatch repair testing is now essential because women with dMMR tumours gain a very large and durable benefit. The gain in mismatch-repair-proficient tumours is real but smaller, and molecular classification (POLE, p53, MMR) is increasingly used to decide who benefits most.
Patients with newly diagnosed advanced stomach cancer should now have Claudin 18.2 tested alongside HER2, PD-L1 and mismatch repair, because roughly a third will be eligible for zolbetuximab, which adds about three months of median survival. The main practical problem is nausea and vomiting during infusions, which needs aggressive prophylaxis. How to sequence or combine it with immunotherapy in PD-L1-positive tumours is unresolved.
Patients whose breast cancer was previously called HER2-negative may now be eligible for an effective HER2-directed drug if their tumour has even low-level HER2 staining, so pathology reports must now distinguish HER2-low (1+ or 2+/ISH-negative) from HER2-zero. This applies to metastatic disease after at least one line of chemotherapy; it does not mean these patients benefit from trastuzumab or other older HER2 drugs.
POLARIX gave the first new first-line standard for DLBCL since rituximab was added to CHOP, and pola-R-CHP is now approved and widely used, especially in higher-risk or ABC-type disease. The gain is modest and survival is unchanged, so many clinicians still use R-CHOP in lower-risk or GCB-type patients. Cost and subgroup uncertainty drive ongoing debate.
Patients with newly diagnosed advanced stomach or oesophageal adenocarcinoma whose tumour is HER2-negative and PD-L1 positive (CPS 5 or more, or at least 1 in some regions) should receive chemotherapy with nivolumab (or pembrolizumab, from KEYNOTE-859), which adds about three months of median survival and doubles the chance of being alive at three years. The benefit in PD-L1-negative tumours is doubtful, and these patients may be better served by chemotherapy alone or by trials.
Every colorectal cancer should be tested for mismatch repair deficiency, because patients whose metastatic tumour is dMMR should receive pembrolizumab rather than chemotherapy as first treatment, gaining a much better chance of durable remission with fewer side effects. About a third of dMMR tumours do not respond initially, so early scans are essential and chemotherapy remains available. The trial does not apply to the 95% of colorectal cancers that are mismatch-repair proficient.
Patients with head and neck squamous cell cancer that has recurred or spread should be treated first with pembrolizumab: alone if their tumour is strongly PD-L1 positive and they can wait for a slower response, or with chemotherapy if the tumour is bulky or PD-L1 low. Cetuximab-based chemotherapy is no longer the default. Long-term follow-up shows a small but real group of patients alive at four to five years, which was almost unheard of before.
Women with newly diagnosed advanced ovarian cancer should have their tumour tested for BRCA mutations and homologous recombination deficiency, because those who are HRD-positive gain years of additional disease control and better survival from adding olaparib to bevacizumab maintenance. Those who are HRD-negative gain nothing from olaparib in this combination and should not be exposed to its toxicity and cost. HRD testing has become a routine part of ovarian cancer care as a result.
Most patients with newly diagnosed advanced non-squamous lung cancer that lacks a targetable mutation should receive chemotherapy plus pembrolizumab; those with PD-L1 of 50% or more may reasonably receive pembrolizumab alone. About one in five patients is alive at five years, compared with roughly one in ten with chemotherapy alone. Patients with EGFR or ALK alterations were excluded and should have targeted therapy first.
This paper established a new regulatory paradigm: a drug approved for a molecular feature regardless of organ. It made MSI/MMR testing standard across advanced cancers and remains the clearest example of a biomarker that works across histologies. It also anchored the idea that mutation load, via neoantigens, is what makes tumours visible to T cells.
Patients with stage III lung cancer that cannot be removed surgically should receive a year of durvalumab after completing chemoradiotherapy, provided they have not progressed. This roughly doubles the chance of being alive without progression at five years. Whether the benefit extends to PD-L1-negative tumours is contested, and the EGFR-mutated subgroup is better served by osimertinib (LAURA).
This small trial explained why colorectal cancer had seemed immune-resistant (most is MMR-proficient) and established the principle that a genomic feature, not the tissue of origin, can predict immunotherapy response. It led directly to the 2017 tissue-agnostic approval of pembrolizumab and to routine MMR/MSI testing of many cancers. Every patient with advanced dMMR cancer should now be considered for checkpoint blockade.
Carrying a cancer mutation is normal; most mutant clones never become cancer. This means blood or tissue tests that look for driver mutations alone will produce false positives, and that the question of what tips a mutant clone into cancer (tissue environment, further hits, immune surveillance) is as important as the mutation itself.
Many older people carry blood clones one or two steps from leukaemia, and those clones also drive heart disease through inflammation. CHIP is why blood-based cancer tests must filter out mutations from blood cells, and it opens a route to preventing both leukaemia and cardiovascular events in carriers.
A single biopsy is an incomplete picture of a patient's cancer. Truncal mutations shared by all cells (in kidney cancer, VHL) are the most reliable drug targets, whereas mutations in only some branches predict resistance. This is why liquid biopsy and multi-region sampling matter.
This study is why PD-1 inhibitors were developed across cancers rather than in melanoma alone: unexpected activity in lung cancer, historically thought immune-resistant, changed drug development priorities industry-wide. It also introduced PD-L1 immunohistochemistry as a candidate biomarker and pneumonitis as a signature toxicity. Within five years PD-1 blockade was approved in more than ten cancers.
Tumours hide from T cells by displaying PD-L1; blocking that interaction lets the immune system attack. This is the mechanism of pembrolizumab, nivolumab, atezolizumab and their relatives, which now treat more than 20 cancer types.