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TMB — Tumor Mutational Burden: The Biomarker That Opens Access to Immunotherapy Regardless of Your Cancer Type
Have you recently received a genetic test report and seen “TMB-High” or “TMB ≥ 10 mut/Mb” written on it and you don’t know what it means? Or did your doctor talk to you about immunotherapy and tell you that you need to determine your “tumor mutational score” first? You’ve come to the right place. This guide explains in a simple way what TMB (Tumor Mutational Burden) is, why it has revolutionized modern oncology, and — most importantly — how it can directly influence your access to immunotherapy, regardless of the organ in which your cancer has developed.
What is, in simple terms, Tumor Mutational Burden (TMB)?
Think of the DNA of tumor cells as a huge text, written in millions of genetic letters. As cancer develops, errors accumulate in that “text”—somatic genetic mutations (acquired throughout life, not inherited). TMB measures exactly how many such “typotypes” there are in each million letters of your tumor’s genetic code.
The more mistakes there are, the more neoantigens the tumor produces —abnormal protein fragments that the immune system can recognize as a “foreign body” and attack. This is the biological reason why tumors with high TMB respond better to immunotherapy: they are more “visible” to immune cells.
TMB is expressed in mut/Mb (number of mutations per megabase of sequenced DNA):
- Low TMB (L-TMB): < 6 mut/Mb
- Intermediate TMB: 6–9 mut/Mb
- High TMB (TMB-H): ≥ 10 mut/Mb (FDA and EMA threshold for tumor-agnostic immunotherapy)
Why is TMB a “tumor type agnostic” biomarker?
This is the revolutionary novelty: TMB works regardless of the cancer’s organ of origin. Unlike markers like PSA (prostate-specific) or CA-125 (ovary-specific), TMB assesses a fundamental property of tumor biology — global genomic instability — present in any type of cancer.
In June 2020, the FDA (US Food and Drug Administration) approved pembrolizumab (Keytruda) for the treatment of any unresectable or metastatic solid tumor with a TMB ≥ 10 mut/Mb that has progressed after prior therapy and has no satisfactory alternatives — regardless of histology or organ of origin. This was the second tumor-agnostic approval in oncology after MSI-H/dMMR.
What cancers most often have high TMB?
Not all tumors accumulate mutations at the same rate. Cancers with high exposure to external mutagens (cigarette smoke, ultraviolet radiation) tend to have much higher TMB than cancers with internal genetic causes:
| Type of cancer | Median TMB (mut/Mb) | % patients with BMT ≥ 10 |
| Cutaneous melanoma | 13–17 | ~50–60% |
| Lung cancer (NSCLC) — smokers | 8–10 | ~40–50% |
| Bladder cancer (urothelial) | 7–10 | ~35–45% |
| MSI-H colorectal cancer | >20 | ~15% of total colorectal |
| Cervical cancer | 4–6 | ~20–25% |
| Breast cancer (TNBC) | 3–5 | ~10–15% |
| Gastric cancer | 4–6 | ~20–25% |
| glioblastoma | 1–2 | <5% |
| Pancreatic cancer | 1–3 | <5% |
💡 Note: Even in cancers with low median TMB, a significant minority of patients may have H-TMB and benefit from immunotherapy—which is why individualized testing matters.
TMB vs. MSI/dMMR — Are they the same thing?
This is one of the most common confusions. They are not identical , although they partially overlap:
| Characteristic | TMB | MSI-H / dMMR |
| What does it measure? | Total number of somatic mutations | Functionality of the DNA error repair system (MLH1, MSH2, MSH6, PMS2) |
| How to detect | NGS (next generation genetic sequencing) | IHC (immunohistochemistry) on biopsy + PCR/NGS |
| superposition | ~20–40% of MSI-H tumors also have TMB-H | MSI-H usually involves elevated TMB, but not always |
| Common cancers | Melanoma, NSCLC, bladder | Colorectal (15%), endometrial (20–40%) |
| Threshold for pembrolizumab | TMB ≥ 10 mut/Mb | Any level of MSI-H/dMMR confirmed |
Practical implication: A patient can be MSI-Stable (MSS) but have TMB-H — and vice versa. Therefore, testing for both biomarkers is recommended in patients who are candidates for immunotherapy, especially if one of them is negative.
How is TMB measured and what test do you need?
TMB is not measured by a simple blood test —it requires comprehensive genomic sequencing (NGS) of tumor tissue or, more recently, plasma (ctDNA liquid biopsy).
Types of tests:
- NGS on tissue biopsy (paraffin block): The gold standard. The panel must cover at least 1 Mb of DNA (ESMO recommendation) for a reliable estimate of TMB.
- FoundationOne CDx: The most well-known comprehensive panel — covers 324 genes + TMB and is FDA-approved as a companion test for pembrolizumab.
- Broad NGS panels: Automatically include TMB calculation alongside other biomarkers (KRAS, EGFR, BRAF, MSI, PD-L1, etc.)
- Blood ctDNA (liquid biopsy): Detects circulating TMB — useful when tissue biopsy is not feasible; slightly lower sensitivity
Is it settled in Romania?
According to the National Cancer Control and Prevention Plan (PNCC), TMB is partially included in the comprehensive NGS panels settled — especially for non-squamous NSCLC lung cancer (Com.Pl.it DX Lung panel, covering 80+ genes), where TMB can be calculated from existing sequencing data.
📋 Practical recommendation: If you have lung, colorectal, gastric cancer or advanced melanoma and comprehensive NGS testing with TMB evaluation has not been recommended, discuss with your oncologist about eligibility for testing reimbursed through the PNCC.
Direct therapeutic implications: How does TMB change physician decision-making?
1. TMB-H ≥ 10 mut/Mb — Access to tumor-agnostic pembrolizumab
The 2020 FDA approval (confirmed by the EMA for Europe) allows the use of pembrolizumab (Keytruda) 200 mg IV every 3 weeks for any solid tumor with TMB-H ≥ 10 mut/Mb , after failure of standard therapy.
Data from the pivotal KEYNOTE-158 study showed:
- Objective response rate (ORR): 29% — significantly higher than standard second-line chemotherapy
- Durable response: Median duration of response was not reached at the time of analysis — some patients remained in remission for years
- Best Answers: Endometrial, Cervical, Thyroid, and Colorectal Cancers with TMB-H
2. TMB in combination with PD-L1 and MSI — A more nuanced decision
The doctor does not evaluate TMB in isolation. Its combination with other biomarkers guides the decision:
| Biomarker profile | Therapeutic implication |
| TMB-H + PD-L1 ≥ 50% | Excellent candidate for first-line monotherapy immunotherapy |
| TMB-H + PD-L1 < 1% | Immunotherapy + chemotherapy combined — more modest benefit |
| TMB-H + MSI-H (double positive) | Exceptional response to pembrolizumab — long-lasting remissions possible |
| TMB-L + STK11 mutant | Less effective immunotherapy — chemotherapy preferred |
| TMB-H + KRAS G12C | Possible combination KRAS inhibitor + pembrolizumab (active clinical trials) |
3. TMB as an independent prognostic factor
Beyond immunotherapy, increased TMB is associated with a higher mutational burden , which may influence:
- Sensitivity to platinum-based chemotherapy (some data suggest benefit in NSCLC and ovarian)
- Eligibility for personalized vaccines based on tumor-specific neoantigens — emerging therapy 2025
- Prediction of the risk of acquired resistance to targeted therapies (tumors with very high TMB may generate resistance mutations more quickly)
BMR Limits — What This Marker Doesn’t Tell You
TMB is not a perfect marker. Knowing its limitations helps you have realistic expectations:
- Not all TMB-H tumors respond to immunotherapy — overall response rate remains at ~30%, not 100%
- There is no universal standardized cutoff — different laboratories and panels may calculate TMB differently; a result of 10 mut/Mb on a small panel is not equivalent to the same score on a comprehensive panel
- TMB does not replace PD-L1 or MSI testing — they are complementary biomarkers, not substitutes
- TMB does not predict immunological toxicity — patients with TMB-H can develop severe immune adverse effects (pneumonitis, autoimmune hepatitis, endocrinopathies) just like any other patient on pembrolizumab
- TMB is not useful in leukemias and lymphomas — where MSI and other biomarkers are more relevant
Practical summary — TMB traffic light for patients
| 🟢 TMB-H ≥ 10 mut/Mb | 🟡 Intermediate TMB 6–9 mut/Mb | 🔴 TMB-L < 6 mut/Mb |
| Eligible for tumor-agnostic pembrolizumab (2nd line) | Uncertain benefit — individualized decision combining PD-L1 and MSI | Immunotherapy monotherapy unlikely as first choice |
| Best candidate if PD-L1 ≥ 50% | May benefit from chemotherapy + immunotherapy | Standard chemotherapy or targeted therapy (if there is an actionable mutation) |
| Eligibility assessment for clinical trials with new combinations | Reconsideration if MSI-H confirmed separately | Parallel testing BRCA, EGFR, KRAS, ALK for targeted therapy |
🧬 TMB — Tumor Mutational Burden: Complete Explanatory Tables for Patients
📊 TABLE 1 — What is TMB, in simple terms
| Term | What does it mean in medical language? | What does it mean to you, by the way? | Why does it matter? |
| TMB (Tumor Mutational Burden) | Total number of somatic mutations per megabase of sequenced DNA | How many “typo errors” are there in your tumor’s genetic code? | The more mistakes, the more visible the tumor is to the immune system |
| Somatic mutation | Acquired genetic change in tumor cells (not inherited) | An “error” accumulated in the DNA of cancer cells throughout life | These errors produce abnormal proteins that the immune system can recognize and attack. |
| Neoantigen | Abnormal protein fragment produced by mutant cells | The “red flag” that the cancer cell involuntarily shows to the immune system | The more neoantigens, the more effective the immunotherapy |
| mute/Mb | The unit of measurement of TMB (mutations per megabase of DNA) | The TMB “score” — the number of mistakes per million genetic letters | Key threshold for immunotherapy: ≥ 10 mut/Mb |
| Tumor-agnostic | Works regardless of the cancer’s organ of origin | The drug approved for TMB works on ANY type of cancer, not just a specific one | FDA approval 2020: pembrolizumab for ANY solid tumor with TMB ≥ 10 mut/Mb |
📊 TABLE 2 — TMB values and what they mean for treatment
| TMB category | Value (mut/Mb) | What does this mean | Immediate therapeutic implication |
| 🟢 High BMR (H-BMR) | ≥ 10 mut/Mb | The tumor has many genetic “mistakes” → it is more visible to the immune system | ✅ Eligible for pembrolizumab (immunotherapy) regardless of cancer type — FDA/EMA approved |
| 🟡 Intermediate TMB | 6–9 mutes/Mb | Zone of uncertainty — benefit of immunotherapy is variable | ⚠️ Individualized decision : PD-L1 and MSI are evaluated to complete the picture; possible benefit with chemotherapy + immunotherapy combinations |
| 🔴 Low BMR (L-BMR) | < 6 mute/Mb | The tumor has few “mistakes” → it is less visible to the immune system | Immunotherapy alone — unlikely as first choice; standard chemotherapy or targeted therapy (if actionable mutation present) |
| ⭐ Very High BMR | ≥ 20 mut/Mb | Tumor with massive genomic instability — the best candidate for immunotherapy | ✅✅ Exceptional response to pembrolizumab ; long- term remissions possible ; especially in MSI – H cancers |
📊 TABLE 3 — Which cancers have high TMB? (Frequency of TMB-H in different types of cancer)
| Cancer Type | Median TMB (mut/Mb) | % patients with BMT ≥ 10 | Why does BMR have a high value? | Clinical relevance |
| 🔵 Cutaneous melanoma | 13–17 | ~50–60% | UV exposure — solar radiation causes massive mutations in DNA | ✅ Best profile for immunotherapy |
| 🫁 NSCLC lung cancer (smokers) | 8–10 | ~40–50% | Cigarette smoke — thousands of mutagenic substances | ✅ High TMB justifies pembrolizumab |
| 🔵 Bladder cancer (urothelial) | 7–10 | ~35–45% | Exposure to urinary carcinogens | ✅ Atezolizumab and pembrolizumab approved |
| 🟢 MSI-H colorectal cancer | > 20 | 15% of total colorectal | Defective DNA repair system → massive accumulation of mutations | ✅✅ Exceptional response — pembrolizumab approved |
| 🔴 Cervical cancer | 4–6 | ~20–25% | HPV-induced mutations + genomic instability | ⚠️ PD-L1 more relevant; Adjuvant TMB |
| 🎗 ️ Breast cancer (TNBC) | 3–5 | ~10–15% | Genomic instability in the triple-negative subtype | ⚠️ TMB useful in specific TNBC subset |
| 🔵 Gastric cancer | 4–6 | ~20–25% | H. pylori infection + MSI instability | ⚠️ MSI more relevant in gastric |
| 🧠 glioblastoma | 1–2 | < 5% | Internal mutations, little influenced by external mutagens | ❌ TMB rarely useful in the brain |
| 🟡 Pancreatic cancer | 1–3 | < 5% | Immunosuppressive environment + few immunogenic mutations | ❌ TMB rarely useful; surgery + standard chemotherapy |
| 🔵 Kidney cancer (clear cell carcinomas) | 3–5 | ~10–15% | Specific mutations (VHL, PBRM1) | ⚠️ Effective immunotherapy through other mechanisms |
💡 Key message for patients: Even in cancers with low median TMB (breast, gastric, cervical), a significant minority of patients may have H-TMB. That’s why individual testing is essential — don’t rely on general statistics!
📊 TABLE 4 — TMB vs MSI/dMMR: Key differences in meaning
| Characteristic | TMB (Mutational Burden) | MSI-H / dMMR (Microsatellite Instability) |
| What does it measure? | TOTAL number of mutations in the tumor | If the DNA error REPAIR system works |
| Simple analogy | How many “typos” are there in the genetic book? | If the “autocorrect” of the genetic book is faulty |
| How is it detected? | NGS (comprehensive genomic sequencing) | IHC (immunohistochemistry) on biopsy — 4 proteins: MLH1, MSH2, MSH6, PMS2 |
| Sample type | Tumor tissue (paraffin block) or blood (plasma) | Tumor tissue only (biopsy or surgical specimen) |
| Do they overlap? | 20–40% of MSI-H tumors also have TMB-H | MSI-H usually involves elevated TMB, but not always |
| Common cancers | Melanoma, NSCLC (smokers), bladder, colorectal MSI-H | Colorectal (15%), endometrial (20–40%), gastric, hereditary colorectal (HNPCC) |
| Threshold for pembrolizumab | ≥ 10 mut/Mb | Any level of MSI-H/dMMR confirmed |
| How specific is it? | Less specific — the intermediate value is ambiguous | More specific — clear positive or negative |
| When is combined useful? | TMB-H + MSI-H = exceptional response to pembrolizumab | MSI stable (MSS) but TMB-H = may benefit from immunotherapy |
| Practical conclusion | Test BOTH of them — they are complementary! | They do not replace each other — different information |
⚠️ Important: A patient can be MSI-Stable (negative) but have TMB-H — and vice versa. The doctor needs BOTH markers for the correct decision.
📊 TABLE 5 — How to measure BMR: types of tests available
| Test type | What is | Sample type | Accuracy | Availability in Romania |
| NGS on tissue biopsy (gold standard) | Sequencing of tumor DNA from paraffin block — panel must cover at least 1 Mb of DNA | Paraffin block (tumor tissue collected during biopsy or surgery) | ✅✅ Highest accuracy | ✅ Available through PNCC for non-squamous NSCLC + other eligible cancers |
| FoundationOne CDx | The most comprehensive panel known — covers 324 genes + TMB + MSI | Paraffin block | ✅✅ International standard approved by FDA | ⚠️ Available privately; costs 2,500 – 4,000 EUR |
| Local NGS panel (Romania) | Comprehensive NGS panels through GeneKor and other laboratories | Paraffin block | ✅ Good if the panel covers > 1 Mb DNA | ✅ Partially settled through PNCC (included in the Lung panel for NSCLC) |
| ctDNA from blood (liquid biopsy) | Circulating tumor DNA — detected from a simple blood sample | Blood (EDTA plasma) | ⚠ ️ Slightly lower sensitivity vs. tissue biopsy | ⚠️ Not PNCC 2025 standard; privately available; useful when biopsy is not feasible |
| IHC (immunohistochemistry) | Detects proteins directly on biopsy — DOES NOT measure TMB directly | Paraffin block | ❌ I do n’t measure TMB | Not applicable for TMB |
📊 TABLE 6 — Therapeutic decision based on the combined TMB + PD-L1 + MSI profile
| Combined tumor profile | What does this mean | Doctor’s decision (2025) | Recommended medication |
| 🟢 TMB-H ≥10 + PD-L1 ≥50% | The tumor is visible to immunity AND actively hides from it | ✅ The best candidate for immunotherapy alone | Pembrolizumab monotherapy (first line) |
| 🟢 TMB-H ≥10 + MSI-H / dMMR | Double positive — anticipated exceptional response | ✅✅ Priority candidate for immunotherapy | Pembrolizumab ± lenvatinib (endometrial cancer); Pembrolizumab monotherapy (colorectal, gastric) |
| 🟡 TMB-H ≥10 + PD-L1 1–49% | Good visibility for immunity but partial concealment | ✅ Chemotherapy + immunotherapy in combination | Pembrolizumab + carboplatin + pemetrexed (NSCLC) |
| 🟡 TMB-H ≥10 + PD-L1 < 1% | Good visibility but minimal concealment — uncertain benefit | ⚠️ Individualized decision ; chemotherapy ± immunotherapy | Platinum-based chemotherapy ± pembrolizumab (second line) |
| 🔴 TMB-L + STK11 mutant | Immunity blocked by STK11 regardless of TMB | ⚠️ Immunotherapy alone is not very effective — preferred chemotherapy | Platinum doublet chemotherapy ± bevacizumab |
| 🟢 TMB-H + KRAS G12C | Two targets that can be operated simultaneously | ✅ Combination KRAS inhibitor + immunotherapy (active clinical trials ) | Sotorasib/adagrasib + pembrolizumab (KRYSTAL trials) |
| 🟡 Intermediate TMB (6–9) + stable MSI | Gray area — insufficient information from isolated TMB | ⚠️ Additional assessment required | BRCA, EGFR, ALK, KRAS testing for alternative targeted therapy |
| 🔴 TMB-L + MSI stable + PD-L1 negative | Tumor with unfavorable immune profile | Standard chemotherapy or targeted therapy if there is an actionable mutation | Chemotherapy; NGS testing for actionable mutations (EGFR, ALK, HER2, etc.) |
📊 TABLE 7 — Tumor-agnostic Pembrolizumab: Clinical data from the KEYNOTE-158 study
| Cancer type (TMB-H ≥10 mut/Mb) | Objective response rate (ORR) | Average response time | Observations |
| Endometrial cancer | ~57% | > 24 months | One of the best answers |
| Cervical cancer | ~29% | > 18 months | Durable response in 1/3 of patients |
| Thyroid cancer | ~22% | > 20 months | Response in poorly differentiated tumors |
| MSI-H colorectal cancer | ~36% | It was not touched. | Long-term remissions possible |
| mesothelioma | ~18% | > 12 months | Option in refractory disease |
| Gastric cancer | ~13% | > 15 months | More effective than 2nd line chemotherapy |
| Breast cancer | ~10% | ~10 months | Limited benefit — more responsive TNBC |
| Lung cancer (NSCLC) | ~29% | > 12 months | Confirmed by KEYNOTE-158 + extensions |
| Global average | ~29% | Untouched at initial analysis | Significantly higher response rates vs. 2nd line chemotherapy in all types |
💡 Meaning: For every 10 patients with TMB-H who receive pembrolizumab, about 3 have a significant response — and often the response is LONG-LASTING (years, not months).
📊 TABLE 8 — What TMB DOES NOT tell you: The limits of the marker in terms of meaning
| Limitation | What does it mean practically? | What does the doctor do? |
| Does not guarantee the answer | The overall response rate is ~29% — 71% of patients with TMB-H do NOT respond to pembrolizumab | Evaluate TMB alongside PD-L1 and MSI for more accurate decision making |
| There is no universal threshold | A TMB of 10 mut/Mb on a small panel ≠ TMB of 10 on a comprehensive panel (FoundationOne) | Your report must specify the method and panel used — the values are not directly comparable |
| Does not replace PD-L1 or MSI | They are complementary biomarkers — each adds distinct information | The doctor needs all three for the optimal decision |
| Does not predict immunological toxicity | Patients with TMB-H can develop severe immune adverse effects (pneumonitis, autoimmune hepatitis, thyroiditis) just like any other patient on pembrolizumab | Strict monitoring of adverse effects under immunotherapy — regardless of TMB |
| Not useful in leukemias and lymphomas | Liquid tumors have different immunorecognition mechanisms | MSI, PD-L1 and other specific markers are preferred in malignant hematopathies |
| Inter-laboratory variability | The same tumor may receive a different TMB score depending on the testing laboratory. | International standardization (ESMO, FDA) is underway — the report must include the method |
| Tumor heterogeneity | Different areas of the tumor may have different TMB | Liquid biopsy (ctDNA) can complement the information from tissue biopsy |
📊 TABLE 9 — What is settled through PNCC in Romania for TMB (2025)
| Type of cancer | Test included | TMB included? | Eligibility condition | Who is doing the report? |
| Non-squamous NSCLC, metastatic/locally advanced | Comprehensive NGS panel (Com.Pl.it DX Long — 80+ genes) | ✅ YES — automatically calculated from NGS data | Non-squamous NSCLC lung cancer + non-smokers squamous, metastatic/locally advanced stage | Oncologist, pulmonologist, thoracic surgeon |
| Squamous NSCLC smokers, metastatic | PD-L1 IHC (clones 22C3, SP263, SP142) | ❌ Not standard | Squamous NSCLC smokers, metastatic stage | Oncologist, pulmonologist |
| NSCLC, operable stages | EGFR + ALK + PD-L1 | ❌ Not standard | Operable stages after complete resection | Oncologist, pulmonologist, thoracic surgeon |
| Colorectal cancer, advanced/metastatic | MSI/dMMR IHC + RAS + BRAF + NTRK + HER2 mutations | ⚠️ Partial ( MSI as proxy) | Newly diagnosed locally advanced or metastatic colorectal cancer | Oncologist |
| High-grade ovarian cancer, stages III–IV | Comprehensive NGS panel (52 genes: BRCA1/2, HRD-GIS, etc.) | ⚠️ Partially included in the panel | High-grade epithelial ovarian carcinoma, stages III–IV | Oncologist |
| HER2-negative, advanced breast cancer | NGS panel 52 genes (BRCA1/2, PIK3CA, NTRK, PD-L1) | ❌ Not standard | HER2-negative, locally advanced or metastatic | Oncologist |
| Gastric cancer, advanced | PD-L1 + HER2 IHC | ❌ Not standard | Gastric or gastroesophageal junction adenocarcinoma, advanced | Oncologist, gastroenterologist |
📋 Practical recommendation: If you have non-squamous NSCLC lung cancer and a complete NGS panel (which also includes TMB) has not been recommended to you, you have the right to ask your oncologist for a report for an NGS panel reimbursed by PNCC . The Com.Pl.it DX Lung panel automatically includes the TMB calculation from the sequencing data.
📊 TABLE 10 — Monitoring response to pembrolizumab (immunotherapy) — Patient guide
| Clinical situation | What is being monitored? | GOOD sign (continue treatment) | ALARM sign (urgently inform the doctor) | At what interval |
| Under pembrolizumab (any cancer) | CT/PET-CT; blood tests | Stable or shrinking tumor; decreasing tumor markers | ⚠️ Tumor growth on 2 consecutive examinations (not on the first one!) — possible pseudo-progression | At 9–12 weeks |
| Pseudo-progression | Repeat CT scan every 4–6 weeks | Tumor that appeared larger but later shrank | ❌ Real increase confirmed at 2 CT → change of treatment | 4–6 weeks after suspicion |
| Immune adverse effects — lungs | Symptoms (dry cough, dyspnea); HRCT | No new pulmonary symptoms | ⚠️⚠️ New dry cough + dyspnea → IMMUNOLOGICAL PNEUMONITIS → immediate stop + corticosteroids | Any time — report immediately |
| Immune adverse effects — thyroid | TSH + T4L every 3 months | Normal TSH (0.4–4 mIU/L) | ⚠️ TSH < 0.1 (hyperthyroidism) or > 10 (hypothyroidism ) → immunological thyroiditis | At 3 months |
| Immune adverse effects — liver | Monthly ALT/AST | ALT/AST < 3x normal | ⚠️ ALT/AST > 5x normal → immunological hepatitis → stop treatment + corticosteroids | Monthly |
| Immune adverse effects — gut | Symptoms (diarrhea, blood in stool) | No persistent diarrhea | ⚠️ Diarrhea > 4 stools/day or with blood → immunological colitis → urgent hospitalization | Any time — report immediately |
| Adverse immune effects — adrenal | Basal cortisol at 3 months | Normal cortisol (> 138 nmol/L in the morning) | ⚠️ Extreme fatigue + hypotension + hyponatremia → adrenal insufficiency → emergency corticosteroids | At 3 months or when symptoms appear |
| Specific tumor markers | CEA (colorectal), CA-125 (ovarian), NSE (SCLC), etc. | Progressive decrease from baseline | ⚠️ Increase > 25% from the minimum value → suspicion of progression | Every 2–3 months |
📊 TABLE 11 — Immunological adverse effects of pembrolizumab: Symptom traffic light
| 🟢 GREEN — Normal, continue treatment | 🟡 YELLOW — Monitoring, inform the doctor at the appointment | 🔴 RED — EMERGENCY — Call your doctor immediately or go to the emergency room |
| Mild fatigue (grade 1) | Moderate fatigue that limits daily activity | Extreme fatigue + hypotension + severe dizziness (adrenal insufficiency!) |
| Mild rash (< 10% body surface area) | Skin rash 10–30% body surface area + itching | Skin rash > 30% body surface area or blisters (Stevens-Johnson!) |
| No respiratory symptoms | Dry cough slightly increased compared to normal | New dry cough + dyspnea + fever → immunological pneumonitis — stop immediately! |
| Normal TSH | Mildly altered TSH (below 0.1 or above 5) | TSH < 0.01 with tachycardia + sweating or TSH > 20 with extreme exhaustion |
| Diarrhea 1–2 stools above normal/day | Diarrhea 3–4 stools/day compared to normal | Diarrhea > 7 stools/day OR bloody stools OR severe abdominal pain |
| ALT/AST < 3x normal | ALT/AST 3–5x normal | ALT/AST > 5x normal + jaundice (yellowing of the eyes/skin) |
| Joints without modifications | Moderate joint pain | Swollen + red joints + severe pain that limits movement |
| Normal vision | Slightly blurred vision | Double vision or sudden loss of vision → immunological uveitis |
📊 TABLE 12 — Essential questions to ask your doctor if you received a TMB result
| If you received this result | MANDATORY questions for the oncologist |
| TMB-H ≥ 10 mut/Mb | “Am I eligible for pembrolizumab based on TMB-H? From which treatment line? Is it reimbursed through the PNCC or the national oncology program?” |
| Intermediate TMB (6–9 mut/Mb) | “Was PD-L1 also tested? What about MSI/dMMR? What combination of biomarkers justifies or excludes immunotherapy in my case?” |
| Low TMB < 6 mut/Mb | “Are there other actionable mutations identified in the NGS panel? (EGFR, ALK, KRAS G12C, BRAF, HER2, NTRK?) What therapeutic alternative is there?” |
| Elevated TMB BUT PD-L1 negative | “Can I benefit from pembrolizumab based on TMB-H even if PD-L1 is negative? What is the anticipated response rate in my case?” |
| Elevated TMB AND STK11 mutant | “Given that I have mutant STK11, which reduces the response to immunotherapy, is chemotherapy more effective as a first choice than pembrolizumab?” |
| High TMB AND MSI-H (double positive) | “How does double positivity TMB-H + MSI-H influence the treatment decision? Can pembrolizumab be combined with lenvatinib in my case?” |
| NGS panel without TMB reported | “Why was the TMB not calculated from my NGS panel? Can it be calculated retroactively or is retesting required?” |
| Any TMB result | “Are there active clinical trials in Romania or Europe for my complete molecular profile (TMB + other identified mutations)?” |
💡 TABLE 13 — Visual Summary: TMB Traffic Light for Patients
| 🟢 TMB-H ≥ 10 mut/Mb | 🟡 Intermediate TMB 6–9 mut/Mb | 🔴 TMB-L < 6 mut/Mb | |
| What does this mean | Many genetic “mistakes” — the immune system can see the tumor | Gray area — insufficient information taken in isolation | Few mistakes — the immune system doesn’t see the tumor well |
| Immunotherapy possible? | ✅ YES — FDA/EMA approved tumor-agnostic pembrolizumab | ⚠️ Depends on PD-L1 and MSI — further evaluation | ❌ Rarely indicated in monotherapy |
| Chemotherapy necessary? | Possibly in combination with immunotherapy | Probably needed in combination | ✅ First choice ( if there is no actionable mutation ) |
| Targeted therapy possible? | Tests BRCA, MSI, PD-L1 complementary | Tests EGFR, ALK, KRAS, HER2 | ✅ Prioritize targeted therapy if there is a mutation (EGFR, ALK, KRAS G12C, HER2) |
| Clinical studies | ✅ Combinations of TMB -H + chemotherapy + immunotherapy | ✅ Studies with emerging combinations | ✅ Studies with SHP2 inhibitors, KRAS non-G12C |
| prognosis | Better under immunotherapy | Variable — depends on the type of tumor | Standard treatment — prognosis determined by other factors |
Disclaimer: The information in these tables is for informational and educational purposes only. It does not constitute a medical diagnosis, does not replace the consultation of a specialist physician, and does not represent a personalized therapeutic recommendation. Drug availability, settlement criteria, and therapeutic protocols are subject to change. Always consult your oncologist before making any medical decisions.
How can Oncoexpertai.com help you?
If your NGS report mentions TMB and you don’t know how to integrate it into the context of the other identified biomarkers — PD-L1, MSI, KRAS, EGFR, or BRCA mutations — the Oncoexpertai.com platform can be your first structured step.
Our advanced Artificial Intelligence algorithms correlate your complete molecular profile with the latest international NCCN, ESMO and EMA 2025 guidelines and generate a structured preliminary analysis. You can find out:
- If your tumor’s TMB-H opens access to pembrolizumab in your current treatment regimen
- What combinations of biomarkers make immunotherapy more or less likely to work in your case?
- What questions to ask your oncologist at your next consultation
Technology does not replace the oncologist — it gives you the certainty that you arrive at the consultation with a complete file and the right questions .
Disclaimer: The information in this article is for informational and educational purposes only. It does not constitute a medical diagnosis, does not replace a specialist doctor’s consultation, and does not represent a personalized therapeutic recommendation. Any medical decision should be made exclusively after consultation with a qualified doctor, based on a complete assessment of your health condition. Reference values, therapeutic thresholds, and medications mentioned may vary depending on updated guidelines and drug availability in Romania — always consult your oncologist.
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Dr. Onisim Florin Senior Medical Oncologist | Founder of OncoExpertAI
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