The Power of a Mutation: Understanding Biomarkers in Cancer Treatment

Let’s start with a story of two patients with the same cancer type. Alan and Bella both have advanced lung cancer. Alan’s doctor tests his tumor and finds a specific mutation in a gene called EGFR. Bella’s tumor doesn’t have that mutation. Alan is given a daily pill (a targeted therapy drug) designed to attack cancer cells with EGFR mutations. Bella, without a targetable mutation, receives standard chemotherapy. Three months later, Alan’s scans show his tumors have dramatically shrunk — the targeted pill is working wonders. Bella’s chemo helped, but her tumor only shrank a little. Why the difference? Because Alan’s cancer had a biomarker that matched a targeted treatment.

This scenario plays out across many cancers today. We are in the era of precision medicine, where details about the specific genes and proteins in a patient’s tumor can determine treatment choices and outcomes. Biomarkers are those measurable traits (like a mutation or protein level) that provide information about a cancer. Some biomarkers are targets for therapy – meaning if your tumor has it, there’s a drug aiming right at that target.

Why Do Mutations Matter?

In this part, we’ll answer: Why do mutations matter? We’ll talk about:

• What biomarkers are, and the different types (genetic mutations, protein expressions, etc.).

• How they’re tested (those extra tests that get run on your biopsy).

• Examples of key biomarkers in various cancers and how they influence treatment (think HER2, EGFR, BRCA, PD-L1, and more acronyms – we’ll decode them).

• Why finding a mutation can sometimes be a stroke of luck (it opens a treatment door), whereas not finding one may limit options.

• The concept of “targeted therapy” and “personalized medicine” – treating the cancer based on its unique molecular fingerprint.

• Q&A to clarify confusing points, like “Does having a mutation mean I inherited something?” or “What if my cancer has no known targets?”

  
  

By the end, you should see your cancer not just as a location and type (like “breast cancer”) but as a collection of unique characteristics (“HER2-positive breast cancer” or “BRCA1-mutant ovarian cancer” etc.), which is critical to understanding why your treatment is what it is.

What Exactly is a Biomarker?

A biomarker in cancer is any measurable biological factor that provides insight into the tumor’s behavior or how it might respond to treatment. The term is broad:

• It can be a gene mutation (a change in the DNA of the cancer cells).

• It can be an extra copy of a gene (amplification).

• It can be a missing gene or broken gene.

• It can be an overproduced protein on the cell surface (like a receptor).

• It can be something in the blood (like a high level of a tumor marker protein).

• It can even be a pattern of gene expression or immune cells presence.

  
  

Biomarkers can play several roles:

Diagnostic biomarkers: Help confirm what type of cancer it is (e.g., certain chromosome changes define specific leukemias).

Prognostic biomarkers: Indicate how aggressive the disease might be (independent of stage/grade, e.g., certain gene signatures in breast cancer show higher recurrence risk).

Predictive biomarkers: Indicate whether a treatment is likely to work. This is often what we mean by “targetable” biomarkers (if you have X mutation, drug Y will likely work).

Monitoring biomarkers: Substances in blood that can be tracked over time to monitor disease status (like PSA for prostate cancer, or CA-125 for ovarian – these are not exactly therapeutic targets but help monitor).

In this article, our focus is on biomarkers that serve as targets or therapeutic guides – the actionable ones.

How Do We Test for Biomarkers?

Back in Part 1, we mentioned that pathology reports often include special tests like immunohistochemistry, FISH, or molecular assays. Those are how biomarkers are detected:

Immunohistochemistry (IHC): A lab technique where they use antibodies to stain for specific proteins in the tissue. If the protein is present (the biomarker), the tissue changes color under the microscope. Example: HER2 protein, ER/PR proteins in breast cancer are tested by IHC. Also, PD-L1 in lung cancer is tested by IHC often.

FISH (Fluorescence In Situ Hybridization): This is used to look for gene amplifications or translocations. Example: HER2 gene amplification is often confirmed by FISH; certain lymphomas have translocations detected by FISH.

PCR and other DNA-based tests: To detect specific known mutations. For instance, some labs do a PCR test for common EGFR mutations in lung cancer.

Next-Generation Sequencing (NGS) panels: This is increasingly common – a broad DNA/RNA sequencing test of hundreds of genes to find any mutations, deletions, fusions, etc. These tests can return a list of mutations in your tumor. Commonly known ones: FoundationOne panel, Oncopanel, etc. These often identify not just standard biomarkers but also rare ones (and sometimes suggest clinical trial options).

Gene expression assays: e.g., Oncotype DX in breast cancer measures the expression of 21 genes to give a recurrence score – that’s a biomarker guiding whether chemo is needed in early breast cancer.

Blood tests (liquid biopsy): There are blood-based biomarker tests too – like checking for circulating tumor DNA to find mutations, or classic tumor markers like AFP, CEA, CA-19-9. But for selecting treatments, typically we look at the tumor tissue (or blood DNA if tumor tissue not available).

So, practically, if you’re diagnosed with, say, metastatic lung cancer, your doctor will send a portion of your biopsy for molecular profiling – that’s how they find if you have EGFR, ALK, ROS1, BRAF, MET, RET, KRAS, etc. mutations or rearrangements. If you have melanoma, they’ll test for BRAF mutation. If you have colon cancer, they test for KRAS/NRAS and BRAF, and check MSI status. If you have breast cancer, they test the original surgical tissue for ER/PR/HER2 (those are biomarkers guiding use of hormone therapy and Herceptin). If you have a certain kind of leukemia, they do cytogenetic analysis or PCR for certain gene fusions (like BCR-ABL in CML, which is the Philadelphia chromosome, target for imatinib).

Each cancer type has known relevant biomarkers to test. Testing is now standard of care in many cases, because it directly impacts treatment decisions.

Why Do Mutations Matter? (Understanding Oncogenes and Tumor Suppressors 101)

Let’s step back to basic biology for a moment. Cancer is a disease of cells growing out of control. Why do they grow out of control? Typically because of mutations in certain critical genes that regulate cell division, DNA repair, cell death, etc.

There are roughly two classes of genes often mutated in cancer:

Oncogenes: These are like gas pedals. When mutated in a certain way (activating mutations), they get stuck ON, driving the cell to proliferate without regard for signals to stop. Example: EGFR gene, when mutated, can send constant “grow” signals. Another: the ALK gene rearrangement creates a fusion that is an always-on signal. Many targeted therapies are designed to block these stuck accelerators.

Tumor suppressor genes: These are like brakes. When they’re lost or inactivated (through mutations or deletions), the cell loses its restraint. Example: TP53 (p53) is a tumor suppressor. When mutated (and it commonly is in cancers), the cell doesn’t properly repair DNA or undergo cell death, enabling more mutations and growth. We currently can’t easily “replace” broken tumor suppressors with drugs (we haven’t got great drugs for, say, “mutant p53” yet). Most current targeted therapies focus on the oncogenes (the “drivers”).

Mutations matter because they can be the root cause of what’s driving that cancer’s growth. If you can identify a driver mutation (particularly an oncogene) and you have a drug that specifically inhibits that driver, you can dramatically slow or stop the cancer – often with fewer side effects than chemo, because you’re hitting a target mostly unique to the cancer.

Analogy: If cancer growth is a speeding car, stage tells you how far the car has gotten, grade tells you how fast it might go, and mutations tell you which wires or pedals are jammed. If you find the jammed accelerator (an oncogene mutation) and can cut that wire, the car slows down or stops. That’s targeted therapy.

Example: In Alan’s lung cancer, the EGFR mutation made an EGFR protein that was constantly signaling the cell to divide. The pill (erlotinib or osimertinib, etc.) he took specifically blocks the EGFR signal in those mutant cells. It’s like throwing a wrench into that particular gear – the cancer cell, addicted to that one major growth signal, now is crippled and often undergoes cell death. His tumors shrank dramatically, more than general chemo likely would have done.

Another example: HER2-positive breast cancer. HER2 is a protein on breast cells that makes them grow. Some breast cancers have too many copies of the HER2 gene (amplification), leading to a ton of HER2 protein. This overexpression drives aggressive tumor growth (HER2-positive breast cancers used to have a worse prognosis). But now, we have Herceptin (trastuzumab) and other anti-HER2 drugs that specifically target HER2. These drugs bind to HER2 and block its function, and also flag the cell for the immune system to attack. The result? HER2+ breast cancer went from one of the nastier subtypes to one of the more treatable, because we have an effective targeted weapon. That biomarker (HER2 amplification) predicts that targeted therapy will work.

Biomarker examples:

Let’s list some common ones across different cancers to see the landscape:

• Breast Cancer: ER (estrogen receptor), PR (progesterone receptor), HER2 status – these dictate use of hormone therapies or HER2-targeted drugs. Also, BRCA1/2 mutation status (if a patient has one in her tumor, or germline, she might benefit from PARP inhibitors).

• Lung Cancer (Non-Small Cell): EGFR mutations, ALK fusions, ROS1 fusions, BRAF mutations, MET exon 14 skipping, RET fusions, KRAS G12C (recently targetable) – each of these now has at least one targeted therapy available. PD-L1 expression is another biomarker used to decide use of immunotherapy; high PD-L1 (≥50%) means immunotherapy (like pembrolizumab) might be very effective even as a single drug.

• Colon Cancer: KRAS/NRAS mutations – if present, avoid EGFR antibody therapy (they predict lack of response). BRAF V600E mutation – indicates poorer prognosis but also a targetable with specific drugs in later lines. Microsatellite instability (MSI) or MMR deficiency – a biomarker for immunotherapy; MSI-high colon cancers respond very well to checkpoint inhibitor immunotherapy, and it also suggests possible Lynch syndrome (an inherited condition) which is important for family.

• Melanoma: BRAF V600 mutation (about 50% of melanomas have it) – targetable with BRAF/MEK inhibitors (dramatically effective in many patients). Also, melanoma is often very immunogenic, so PD-L1 and tumor mutation burden are considerations for immunotherapy, though in melanoma immunotherapy is often used regardless of PD-L1 because they tend to respond.

• Leukemias: Chronic Myeloid Leukemia (CML) has BCR-ABL fusion (Philadelphia chromosome) – imatinib (Gleevec) targets that and turned CML from fatal to a chronic often well-controlled disease. Acute Promyelocytic Leukemia (APL) has PML-RARA fusion – treated with ATRA and arsenic targeting that specifically (very high cure rates now).

• Lymphoma: Some subtypes have CD20 protein – targeted by rituximab (an antibody). That's not a mutation but a protein marker on the cell surface (CD20 biomarker present = can use anti-CD20 immunotherapy).

• Ovarian Cancer: BRCA1/2 mutations (either germline or somatic) – predict response to PARP inhibitor drugs, which can cause long remissions in such patients. Also, if the tumor has “HRD” (homologous recombination deficiency, often overlapping with BRCA), those drugs work well.

• Prostate Cancer: Androgen receptor (AR) is a target (hormone therapies target AR signaling), and now PARP inhibitors are approved for those with BRCA or other DNA repair mutations in prostate cancer too. Also, PSA is a biomarker to monitor, though not a target per se.

• Gastrointestinal stromal tumors (GIST): Often have c-KIT mutations – imatinib targets KIT and is very effective in those.

• Pancreatic Cancer: Fewer common targets, but about 1-2% have an ALK or ROS1 or NTRK fusion (if so, can treat like lung targeted). Also, a subset has MSI-high (immunotherapy option).

• Any cancer: If it’s MSI-high or TMB (Tumor Mutational Burden) high, it may respond to immunotherapy (that’s why pembrolizumab is approved for any MSI-high solid tumor, a landmark “tissue-agnostic” indication).

• Any cancer with NTRK fusion: This is a rare mutation but across many cancer types. There’s a drug (larotrectinib) approved for any tumor that has an NTRK gene fusion, with often superb responses, because that fusion is a strong driver but rare (like some very rare salivary or pediatric tumors, or rare cases of common cancers).

• Hematology example again: If a patient’s lymphoma is “DLBCL ABC subtype with double-hit MYC and BCL2” (some technical info), that is a biomarker scenario indicating they might need more aggressive chemo or a trial – it’s prognostic mainly. So some biomarkers aren’t targetable but stratify risk (like "double-hit" lymphoma is high risk).

  
  

This list goes on. It’s indeed a lot of jargon, but the point is: depending on your cancer type, certain biomarkers will be looked for. If one is found and there is a known effective targeted therapy, that can significantly shape your treatment.

Q&A about Biomarkers:

Q: “My doctor said they’re sending my tumor for mutation testing. What are they looking for and how does it help me?”

A: They’re looking to see if your tumor has any known driver mutations or markers that we have specific treatments for. For example, in lung cancer, they’ll test EGFR, ALK, and others. If one is positive, you might take a pill that targets that mutation, which often works better and is less toxic than chemo. If none are found, you’ll likely get more standard chemo or immunotherapy based on other factors. It also might check if you have markers indicating you could get immunotherapy (like PD-L1). In short, they’re trying to personalize your treatment rather than using one-size-fits-all.

Q: “They said my cancer is HER2-positive. What does that mean?”

A: HER2-positive means your cancer cells have more HER2 receptors than normal (either from gene amplification or other mechanism). It’s common in about 20% of breast cancers and also some stomach cancers. It used to mean a more aggressive cancer, but now it means we have specific medications (like trastuzumab/Herceptin, pertuzumab, and newer ones) that latch onto HER2 and block it, which can dramatically improve outcomes. So HER2-positive has become a treatable feature. It’s good that we know it, because your treatment will include those targeted drugs, which improve your chance of cure (in early stage) or prolong survival (in advanced stage) significantly.

Q: “My report mentions something about PD-L1 60%. What is that?”

A: PD-L1 is a protein some cancer cells express that can suppress the immune system’s attack. Immunotherapy drugs called checkpoint inhibitors (like pembrolizumab/Keytruda) release the brakes on the immune system to fight the cancer. Studies found that if a tumor has a high level of PD-L1 (like “60% of cells positive”), the immunotherapy is more likely to work, particularly in lung cancer. So a PD-L1 of 60% is considered high; that means you are a good candidate for immunotherapy. For example, in advanced lung cancer with PD-L1 >50%, often they’ll give immunotherapy alone without chemo first, because response rates are high. In other cancers (like head & neck or bladder), they also use PD-L1 to guide immunotherapy decisions. So PD-L1 is a predictive biomarker for immunotherapy benefit.

Q: “What is MSI or MMR testing? My doctor ordered that for my colon tumor.”

A: MSI stands for Microsatellite Instability. MMR stands for MisMatch Repair (the system that corrects DNA typos). Some colon (and other) cancers have a defect in this system, leading to lots of mutations – we call them MSI-high or MMR-deficient. Why it matters: - It can indicate a possibility of Lynch syndrome if in colon/endo cancers (an inherited condition, important for family screening). - Tumors that are MSI-high have tons of mutations, which makes them more visible to the immune system. And indeed, immunotherapy has been very effective in such cases. So if your tumor is MSI-high, and if it’s advanced, immunotherapy could be an option that might even be better than chemo. - In early stage, MSI-high sometimes means less benefit from standard chemo (like 5FU doesn’t work as well in stage II MSI-high colon, which is interesting). So, MSI is a biomarker for using immunotherapy (FDA approved immunotherapy for any MSI-high solid tumor that’s advanced). It’s also kind of prognostic and diagnostic for Lynch.

Q: “They said no targetable mutation was found. Does that mean my cancer can’t be treated?”

A: Not at all. It just means we don’t have a nifty magic bullet pill specifically for your tumor’s mutations (or your cancer might be driven by things we can’t target yet). Most cancers historically have been treated with standard methods (surgery, chemo, radiation) which still work quite well even without a specific mutation target. We do mutation testing to leave no stone unturned – if something actionable is there, great, we’ll use it. If not, we rely on the broader therapies. Also, absence of a mutation might steer therapy too (like in colon cancer, if no KRAS mutation = then an EGFR antibody might work; if KRAS mutated, that drug wouldn’t work). So, negative results still inform us what not to do. Moreover, research is ongoing; even if you have no target now, you might be eligible for a clinical trial of a new drug if your tumor has some novel finding. Your oncologist will still outline a full plan – it just might be the more traditional approach.

Q: “My tumor had a BRCA mutation. Isn’t that a genetic thing? What does it mean for my treatment?”

A: BRCA1 and BRCA2 are genes that when mutated in the germline (inherited) cause higher risk of breast/ovarian/prostate/pancreatic cancers. Some people inherit a defective BRCA gene – that’s something you’d do genetic counseling for, because it has implications for family and possibly preventive surgeries. But here we’re talking likely about the tumor having a BRCA mutation – which could either mean you have an inherited one or sometimes the tumor itself acquired a BRCA mutation. Either way, tumors with BRCA mutations (or similar DNA-repair mutations) are often sensitive to a class of drugs called PARP inhibitors. These drugs exploit the cancer’s weak DNA repair to kill it (concept called “synthetic lethality”). For example, ovarian cancers with BRCA mutations respond very well to PARP inhibitors like olaparib, which can keep the cancer controlled for a long time. Breast cancer with BRCA can also use PARP inhibitors in some cases. So this biomarker opens up a targeted therapy option. Also if it is germline, it influences maybe surgical decisions (like perhaps removing the other breast prophylactically, etc., though that’s more in early stage context).

Q: “What is a ‘targeted therapy’? Is it like chemo?”

A: Targeted therapy refers to drugs that specifically block a certain abnormal protein or pathway that the cancer cells depend on, as opposed to classic chemotherapy which blasts all rapidly dividing cells in a more general way. Targeted therapies can be pills or IV drugs, often with different side effect profiles than chemo. For instance, a targeted pill might cause a rash or liver enzyme changes, whereas chemo causes hair loss and low blood counts. Targeted therapies usually are given to people whose tumors have the target – that’s why testing is needed. They can sometimes produce dramatic results, especially in patients with metastatic disease where chemo might have only modest effect, a targeted drug can cause tumor regressions and prolonged control. However, cancers can develop resistance to targeted therapies too (like new mutations that bypass the drug’s effect). Still, targeted therapy has revolutionized treatment for many subgroups of patients. It’s not necessarily “milder” than chemo – some are easier, some have their own serious side effects – but often they’re better tolerated and you avoid things like hair loss or big nausea.

Q: “My friend’s lung cancer had an ALK mutation and she takes a pill and is doing well. I have the same type of lung cancer but no ALK mutation; can I get that pill?”

A: The pill (like crizotinib or alectinib for ALK) specifically works for cancers driven by ALK fusions. If your cancer doesn’t have that ALK fusion, that drug won’t help your cancer; your friend’s good outcome is tied to matching the drug to the mutation. Instead, if you have another mutation (say EGFR or ROS1), you’d get a different pill; if you have none, immunotherapy or chemo is used. So targeted drugs are not one-size-fits-all; they’re matched to the right patient’s tumor. Giving an ALK inhibitor to an ALK-negative patient would likely just give side effects and no benefit. That’s why testing is crucial to identify who should get what.

Q: “What if new mutations are discovered in the future? Should I be retested?”

A: Possibly, especially if your disease progresses. Sometimes we do a new biopsy on relapse to see if new targets emerged or if the tumor changed. Also, research is always finding new markers. For example, KRAS G12C just got a drug recently; prior to 2021, KRAS was “undruggable”. Now if someone’s tumor has KRAS G12C, there’s a pill for that in lung cancer. So if you were tested years ago, it might be worth re-checking if new therapies have come up (with doctor’s guidance). Also, if you had targeted therapy and it stops working, re-biopsy can show a resistance mutation that might be targetable by another drug. The field evolves, so yes, sometimes retesting is part of ongoing care.

Q: “Are there biomarkers that mean I shouldn’t get a certain treatment?”

A: Yes. For example, colon cancer: if RAS mutation is present, then anti-EGFR antibodies like cetuximab won’t work, so we don’t give them. That mutation is a biomarker of resistance to that drug. Another: In breast cancer, if a tumor is HER2-negative, giving Herceptin (anti-HER2) would be pointless. Or if a breast cancer is ER-negative, hormone pills like tamoxifen won’t help. So biomarkers can also spare you treatments that wouldn’t benefit you. Similarly, if a patient’s tumor is MSS (microsatellite stable, not MSI-high), giving immunotherapy outside of some specific contexts is less likely to work, so you’d lean more on chemo.

Q: “Is an inherited mutation (like BRCA in me) a biomarker for treatment too?”

A: Yes, often. If you personally have a germline BRCA mutation and you develop cancer, that often means the cancer’s cells also have lost that BRCA function, making them vulnerable to certain treatments like PARP inhibitors. So even though that mutation is in all your cells, it’s playing out in the cancer’s biology. We call those “germline biomarkers” sometimes. Another example: germline TP53 (Li-Fraumeni syndrome) means those tumors might behave differently or be sensitive in certain ways. Also, inherited mutations help identify which targeted preventions or screenings to do for you and family (beyond current treatment).

Q: “What about the cost and time? Does waiting for these biomarker test results delay treatment?”

A: It can take a couple weeks to get comprehensive molecular profiling results, depending on the test and lab. In most metastatic cases where targeted therapy is relevant, waiting for results is worthwhile to choose the right initial therapy. Oncologists will judge if it’s safe to wait – usually it is, but if someone’s really ill from cancer, they might start some treatment (like chemo) while awaiting results, and then switch if a targetable mutation is found. Many times, especially in lung cancer now, they want to get that info upfront because if you start chemo and then a week later find an EGFR mutation, you would have rather started the pill, etc. So, slight delay for critical info is acceptable. There are also rapid tests for key mutations sometimes. Insurance generally covers biomarker tests recommended by guidelines. Many companies also have assistance programs to ensure testing is accessible.

Q: “If my cancer has no known targets now, might there be clinical trials I should consider?”

A: Absolutely. Trials often focus on particular molecular subsets. There are also “basket trials” where any cancer with a certain mutation can receive an experimental drug (like a trial of an FGFR inhibitor might take patients with FGFR mutations from any tumor type). If your standard options are limited, genomic testing might reveal a mutation that, while not targetable with approved therapy, is eligible for a trial. Even if not, your profile might match a research study. It’s always worth asking your oncologist about trials, especially if frontline treatments aren’t working.

Personalized Medicine: Changing Mindset from “One Disease” to “Many Sub-diseases”

In the not-so-distant past, we categorized cancers mainly by location and type (breast, lung, colon, etc., and their histological type). Now, within each of those, we think in subgroups:

• “I have lung adenocarcinoma” is not enough – they’ll say “EGFR-mutant lung adenocarcinoma” or “ALK-fusion lung adenocarcinoma”, etc., because the treatment course diverges completely based on that.

• Two patients both “Stage IV lung cancer” could get totally different treatments and have different prognoses depending on their biomarkers.

• Even in early stage, biomarkers can matter: e.g., after surgical removal of an EGFR-mutant lung cancer, they now often give an EGFR-targeted pill for 3 years to reduce relapse, which they wouldn’t do if that mutation wasn’t there.

  
  

The promise and the challenge: For patients, if your tumor has a targetable driver, that’s a hopeful sign – a chance for a more effective, tailored therapy. However, targeted therapies aren’t a permanent cure usually; cancer can become resistant. It might shrink and then some cells with different mutations grow (we often then find a second mutation that made the drug stop working, and sometimes have a second targeted drug for that!). So it can be like chasing the next weakness as the cancer adapts.

But many patients live significantly longer and better due to these new therapies. For example, metastatic melanoma median survival used to be under a year; now with BRAF/MEK pills or immunotherapy, many patients live several years, some even appear cured. Chronic myeloid leukemia was nearly universally fatal in a few years; now most patients, on a daily targeted pill, have near-normal lifespan and excellent quality of life. It’s truly a game changer to find “the mutation that matters” in your cancer.

Role of Biomarkers in Prognosis vs Prediction (linking to Part 4’s theme):

• Some biomarkers are purely prognostic: e.g., a gene signature might say “high risk of recurrence” but we might not have a specific drug for that, it just tells us maybe use chemo.

• Some are predictive of response: e.g., ER-positive predicts response to hormone therapy, EGFR mutation predicts response to EGFR inhibitors, etc.

• Some are both prognostic and predictive: e.g., HER2-positive historically was prognostic (worse outcome) but also predictive (targeted therapy works on it and improves outcome).

• Knowing what is driving your tumor gives a sense of “how bad is it?” and “how can we stop it?” For instance, an ALK-driven lung cancer tends to occur in younger patients, often it’s very sensitive to ALK inhibitors (good predictive), but if untreated, ALK+ can be aggressive (so somewhat prognostic that way, but the drug changes that outcome drastically).

  
  

Summing Up Part 3:

• Biomarkers are characteristics of your cancer that can inform therapy.

• Mutations matter because they can be specific Achilles’ heels of the cancer. A targeted therapy is like an arrow hitting that Achilles’ heel.

• We now commonly test tumors for panels of mutations or markers to ensure no option is missed.

• “Personalized medicine” means your treatment plan might be unique to the molecular make-up of your tumor, not just the general type and stage.

• Patients should feel empowered to ask, “Has my tumor been tested for mutations or special markers?” as one of the key questions (spoiler: that’s going to be one of the “10 questions to bring to your next visit” in Part 5!). If not, ensure it’s considered, especially in advanced cancers.

• If a biomarker is found, you and your doctor can discuss targeted therapy or other implications (like genetic testing for family if it’s something like BRCA).

• If no biomarker is found, don’t be discouraged – research is ongoing, and standard treatments can still be very effective. Plus, you might consider trials or retesting later.

• Always keep an ear out for new developments – the landscape changes fast. For example, if you had “undruggable” KRAS in lung cancer a few years ago, now at least one subtype of that (G12C) became druggable. More are coming.

  
  

As we continue with the series, keep in mind how Part 1 (pathology) + Part 2 (stage/grade) + Part 3 (biomarkers) all layer together to paint a full picture of one’s diagnosis:

• Pathology gave the general type and key features.

• Stage/grade gave the extent and aggressiveness.

• Biomarkers gave the specific unique traits and vulnerabilities.

  
  

Armed with this, one can almost predict the next step: Prognosis vs Prediction (Part 4) – which is about interpreting what all these factors mean in terms of outcomes, without seeing them as a crystal ball of fate but as probabilities and possibilities. We will discuss how doctors use all this information to talk about your outlook and why it’s not a prophecy set in stone.

Then in Part 5, we’ll guide you on questions to ask – many of which tie directly to pathology, staging, and biomarkers, to ensure you fully understand your diagnosis and treatment plan.

Stay tuned for Part 4, where we confront the difference between prognostic statistics and personal outcomes – “probability, not prophecy.”