How To Read A Tempus Report

Understanding a Tempus report is a critical skill for oncologists, pathologists, and healthcare providers navigating the complexities of precision oncology. Here's the thing — these comprehensive genomic profiling results translate complex molecular data into actionable clinical insights, guiding therapy selection, clinical trial eligibility, and disease monitoring. Mastering the layout, terminology, and clinical significance of each section ensures that the wealth of data generated by next-generation sequencing (NGS) translates into personalized patient care rather than overwhelming noise Easy to understand, harder to ignore..

And yeah — that's actually more nuanced than it sounds.

The Structure of a Tempus Report

A standard Tempus report—whether derived from the Tempus xT (tissue-based solid tumor assay), Tempus xF (liquid biopsy), or Tempus nP (neuropsychiatric) platforms—follows a logical flow designed for clinical utility. While specific layouts may update over time, the core architecture remains consistent: a high-level summary followed by granular molecular findings, clinical interpretations, and supporting technical data That alone is useful..

1. Patient and Specimen Summary

The first page serves as the anchor. It verifies patient demographics, ordering physician, and—crucially—specimen adequacy. Always verify the specimen type (FFPE tissue, blood, bone marrow) and the tumor cellularity percentage. Low tumor cellularity or insufficient DNA/RNA yield can impact sensitivity, particularly for detecting subclonal variants or copy number alterations. This section also lists the assay version (e.g., xT v4.0), which defines the gene panel size and analytical capabilities relevant to the report date Easy to understand, harder to ignore..

2. Clinical Actionability Summary (The "At-a-Glance" Page)

This is often the most referenced page during tumor boards. It distills hundreds of data points into three categorized tiers based on guidelines from AMP/ASCO/CAP and NCCN:

• Tier I (Strong Clinical Significance): Variants with FDA-approved therapies for the patient’s specific tumor type (Level A) or other tumor types (Level B). These represent the highest priority for treatment decisions.
• Tier II (Potential Clinical Significance): Variants with compelling preclinical data, early-phase clinical trial data, or FDA approval in a different cancer type. This includes biomarkers predicting response or resistance to standard therapies (e.g., KRAS G12C in non-small cell lung cancer vs. colorectal cancer).
• Tier III/IV (Uncertain or Benign Significance): Variants of Unknown Significance (VUS) or benign polymorphisms. Do not make treatment decisions based solely on Tier III/IV findings.

Pro Tip: Pay close attention to the "Biomarker Highlights" box. It flags critical positive and negative findings, such as Microsatellite Instability-High (MSI-H), Tumor Mutational Burden (TMB-H), or the absence of EGFR sensitizing mutations in lung adenocarcinoma.

Deep Dive: Genomic Findings Sections

Beyond the summary, the report body provides the evidentiary backbone. Reading these sections requires understanding the variant classification nomenclature.

3. Somatic Variants (Small Variants: SNVs/Indels)

This table lists single nucleotide variants (SNVs) and small insertions/deletions (indels). Key columns to analyze:

• Gene & Alteration: e.g., TP53 p.R175H.
• Variant Allele Frequency (VAF): The percentage of sequencing reads supporting the variant. A VAF near 50% suggests a heterozygous clonal event; a VAF near 100% may indicate loss of heterozygosity (LOH); a low VAF (<5-10%) suggests subclonality or potential contamination/artifact.
• Clinical Annotation: Tempus provides a brief evidence statement citing specific drugs, trials, or guidelines (NCCN, ESMO). Cross-reference the citation. A drug approved for BRAF V600E melanoma may not be indicated for BRAF V600E colorectal cancer due to differential pathway feedback mechanisms.

4. Copy Number Alterations (CNAs) and Focal Amplifications/Deletions

NGS algorithms infer copy number changes from depth of coverage. Look for:

• Focal Amplifications: High-level gains in oncogenes (ERBB2/HER2, MET, EGFR, CDK4/6, FGFR1/2/3). These are often highly actionable.
• Homozygous Deletions: Complete loss of tumor suppressors (CDKN2A/B, PTEN, SMAD4). CDKN2A loss, for example, may predict sensitivity to CDK4/6 inhibitors in specific contexts or indicate aggressive biology.
• Whole Arm/Chromosome Changes: Large-scale events (e.g., Chr 7 gain / Chr 10 loss in glioblastoma) are often prognostic rather than directly targetable.

5. Gene Fusions and Structural Variants (RNA-Based)

This is a distinct advantage of the Tempus xT assay (DNA + RNA). RNA sequencing detects expressed fusions regardless of intron size or breakpoints The details matter here..

• Read the Fusion Partner: The 5' partner drives expression; the 3' partner provides the kinase domain. EML4-ALK is targetable; a novel ALK fusion with an unknown partner requires functional validation.
• Expression Support: The report lists "Supporting Reads" or "Fusion Transcripts per Million." Higher expression correlates better with protein expression and drug response.
• Splice Variants: RNA-seq also catches exon skipping events (e.g., MET exon 14 skipping) which DNA-only panels frequently miss.

6. Genomic Signatures: MSI, TMB, and HRD

These aggregate biomarkers are calculated algorithmically and are important for immunotherapy and PARP inhibitor decisions It's one of those things that adds up..

• Microsatellite Instability (MSI): Reported as MSI-High (MSI-H), MSI-Stable (MSS), or Indeterminate. MSI-H is a tissue-agnostic FDA approval marker for pembrolizumab. Check the MMR protein status (IHC) correlation if available.
• Tumor Mutational Burden (TMB): Reported as mutations per megabase (mut/Mb). Tempus uses a validated algorithm (often ~1.3 Mb coding region). Note the TMB threshold used (e.g., ≥10 mut/Mb for pembrolizumab in solid tumors). Be aware that TMB-H in certain cancers (e.g., breast, prostate) has less established predictive utility than in NSCLC or melanoma.
• Homologous Recombination Deficiency (HRD): Often reported as a "Genomic Instability Score" (GIS) or "LOH/TAI/LST" scores. A "Positive" HRD status (usually GIS ≥ 42 or similar cutoff) supports PARP inhibitor use in ovarian, breast, prostate, and pancreatic cancers, especially alongside BRCA1/2 mutations.

Interpreting Germline Findings

Tempus reports typically include a dedicated Germline Section if matched normal sequencing (blood/saliva) was performed or if pathogenic variants are detected incidentally in the tumor-only assay with high VAF suggestive of germline origin Worth keeping that in mind..

• Actionable Germline Findings: Pathogenic variants in BRCA1/2, Lynch syndrome genes (MLH1, MSH2, MSH6, PMS2, EPCAM), TP53 (Li-Fraumeni), ATM, CHEK2, PALB2.
• Cascade Testing Implications: A positive germline finding mandates genetic counseling and cascade testing for relatives. This changes the report from a somatic diagnostic tool to a hereditary cancer risk assessment document

Clinical Actionability and Treatment Decision‑Making
When a somatic alteration is identified, the next step is to map it to therapeutic options, clinical trials, or resistance mechanisms. Tempus xT provides an “Actionability” tier that stratifies findings as follows:

Integrating RNA‑Based Findings
Because the assay captures both DNA and RNA, discordant results can arise—for instance, a DNA‑level fusion breakpoint that is not transcribed, or an expressed splice variant invisible to DNA‑only sequencing. In practice:

• Concordant DNA + RNA events (e.g., EGFR exon 20 insertion detected at the DNA level and confirmed by aberrant transcript) confer the highest confidence for targeted inhibition.
• DNA‑only events lacking RNA support may reflect low transcriptional activity, subclonal presence, or technical artifacts; functional validation (e.g., RT‑PCR) is advisable before committing to a therapy that depends on expression.
• RNA‑only events (such as MET exon 14 skipping or novel fusions) often indicate a driver that would be missed by DNA‑centric panels, prompting consideration of MET inhibitors or trial enrollment despite a wild‑type DNA profile.

Germline Findings: From Risk to Management
The germline section of the report is not merely an ancillary note; it can reshape patient and family care pathways:

1. Confirmatory Testing – Any pathogenic or likely pathogenic germline variant reported from tumor‑only sequencing should be validated in a certified CLIA‑lab using germline‑specimen DNA (blood or saliva) to exclude somatic mosaicism or clonal hematopoiesis.
2. Guideline‑Driven Surveillance – For genes such as BRCA1/2, PALB2, or Lynch syndrome loci, national guidelines (NCCN, ESMO) prescribe specific cancer‑screening regimens (e.g., breast MRI, colonoscopy) and risk‑reducing interventions (e.g., prophylactic salpingo‑oophorectomy).
3. Therapeutic Implications – Germline BRCA1/2 mutations can render tumors sensitive to PARP inhibitors irrespective of somatic status, while germline MSH2/MSH6 defects may predict response to immunotherapy in endometrial or colorectal cancers.
4. Family Communication – Genetic counselors should make easier cascade testing, discuss penetrance, variant reclassification potential, and psychosocial considerations. Documentation of the germline finding in the electronic health record ensures that future providers are aware of the hereditary risk.

Report Limitations and Quality Indicators
Even with a solid DNA + RNA platform, clinicians should be aware of certain caveats that affect interpretation:

• Tumor Purity and Subclonality – Low tumor cellularity can diminish VAF, pushing true drivers below the assay’s detection limit; the report often includes an estimate of tumor fraction, which aids in judging whether a negative result is reliable.
• Sequencing Depth – While the assay targets ~600 genes at >500× coverage, certain GC‑rich or repetitive regions (e.g., KRAS exon 2, FLT3 internal tandem duplications) may still suffer from dropout; confirmation with orthogonal methods (PCR, Sanger) is advisable for critical hotspots.
• RNA Quality – Degraded RNA can reduce fusion detection sensitivity; the report typically provides an RNA integrity number (RIN) or a metric such as “median 3’/5’ coverage ratio.” Low values should temper confidence in negative RNA‑based calls.
• Algorithm‑Dependent Biomarkers – MSI, TMB, and HRD scores rely on bioinformatic pipelines that may differ between platforms; cross‑institutional comparison requires awareness of the specific cut‑offs and reference genomes used.
• Incidental Findings – The assay may uncover variants unrelated to the oncology indication (e.g., pharmacogenes like DPYD or

or UGT1A1) that have actionable implications for toxicity management, which must be flagged and communicated to the primary care team.

Conclusion

The integration of comprehensive genomic profiling, encompassing both tumor and germline analysis, marks a key shift in oncology towards truly personalized medicine. By systematically identifying hereditary cancer predisposition, clinicians can move beyond treating the individual patient to managing a familial risk. This holistic approach enhances diagnostic precision, guides targeted surveillance and risk-reducing strategies, and unlocks tailored therapeutic options, such as PARP inhibitors and immunotherapy. While the interpretation of these complex results demands careful attention to technical limitations and requires solid multidisciplinary collaboration, the ultimate benefit is a proactive, preventive care model that improves outcomes for patients and their at-risk relatives alike. The future of oncology lies not only in conquering cancer but in preventing it through the power of genetic insight But it adds up..