Q (haiku): What is the current and future support for storing and analyzing germline variants in cBioPortal, compared to other alternatives?

▶ read_guide
{
 "uri": "cbioportal://germline-guide"
}

◀ result
Germline Variant Guide
======================

Overview
--------
cBioPortal stores both somatic AND germline variant data. Many cBioPortal features work identically for both variant types. This guide explains how to query germline variants and what to be aware of.

How Germline Data is Stored
---------------------------

### mutation_status is free text — always compare case-insensitively
Each study loads its own spelling. Germline calls appear as `'Germline'`, `'GERMLINE'` and `'germline'`; somatic calls as `'Somatic'`, `'SOMATIC'` and `'somatic'`; unannotated mutations as `'NA'`, `'.'`, `'Unknown'`, `'UNKNOWN'`, `'__UNKNOWN__'` and others. Matching one spelling silently drops whole studies (`mutation_status = 'Germline'` misses `all_stjude_2013`, `aml_stjude_2024` and `pog570_bcgsc_2020`).

- **Germline:** `upper(mutation_status) = 'GERMLINE'`
- **Somatic:** `upper(mutation_status) = 'SOMATIC'` — but only when the user asks for somatic-only. Many studies label their somatic calls `'NA'` or `'UNKNOWN'`, so for ordinary mutation questions follow common-pitfalls #3 and exclude only `'UNCALLED'`.
- When unsure, list the values first: `SELECT mutation_status, count() FROM genomic_event_derived WHERE cancer_study_identifier = '{study_id}' AND variant_type = 'mutation' GROUP BY mutation_status`

### Where the column lives
- `genomic_event_derived.mutation_status` (preferred): mutations, and structural variants (from `sv_status`: `'SOMATIC'`, `'Somatic'`, `'GERMLINE'`)
- `mutation_derived.mutationStatus`: the same values for mutations

Identifying Studies with Germline Data
--------------------------------------
Not all studies include germline data. Always check before querying:

```sql
-- Find studies containing germline mutations
SELECT cancer_study_identifier, COUNT(*) as germline_count
FROM genomic_event_derived
WHERE variant_type = 'mutation'
  AND upper(mutation_status) = 'GERMLINE'
GROUP BY cancer_study_identifier
ORDER BY germline_count DESC
```

Common Query Patterns
---------------------

### Count germline vs somatic mutations per gene in a study
```sql
SELECT hugo_gene_symbol, upper(mutation_status) AS status, COUNT(*) as count
FROM genomic_event_derived
WHERE cancer_study_identifier = '{study_id}'
  AND variant_type = 'mutation'
  AND upper(mutation_status) IN ('GERMLINE', 'SOMATIC')
GROUP BY hugo_gene_symbol, status
ORDER BY count DESC
LIMIT 20
```

### Find patients with germline mutations in a specific gene
```sql
SELECT DISTINCT patient_unique_id, sample_unique_id, mutation_variant, mutation_type
FROM genomic_event_derived
WHERE hugo_gene_symbol = '{GENE}'
  AND upper(mutation_status) = 'GERMLINE'
  AND cancer_study_identifier = '{study_id}'
  AND variant_type = 'mutation'
```

### Germline mutation frequency
The numerator is samples with a germline mutation in the gene; the denominator is samples **profiled** for the gene — not samples that happen to have a mutation in it. Take the denominator from mutation-frequency-guide Step 2 (or … (2222 more chars)

═ answer (success)
Based on cBioPortal's documentation, here's the current state of germline variant support:

## Current Support (Today)

**cBioPortal stores and can analyze germline variants**, but with important limitations:

### What's Supported
- **Storage:** Germline variants are kept in `mutation_status` and `sv_status` columns and can be queried alongside somatic data
- **Query tools:** Standard cBioPortal features work for germline variants:
  - Mutation frequency queries (with status filtering)
  - Protein domain analysis
  - Clinical correlation (joining with clinical attributes)
  - Co-occurrence/exclusivity patterns
  - Web interface visualization (OncoPrint, Mutations tab)
- **Identification:** You can filter germline vs. somatic using case-insensitive `mutation_status` matching (e.g., `upper(mutation_status) = 'GERMLINE'`)

### Current Limitations
1. **Not all studies include germline data** — many filter it out during processing; you must verify before querying
2. **Inconsistent annotation** — germline data may lack `mutation_status` labels entirely (marked as `'NA'`, `'UNKNOWN'`), making silent loss of data a risk
3. **No ACMG classification storage** — pathogenicity (pathogenic, likely pathogenic, VUS) is not stored in standard cBioPortal columns
4. **Driver annotations missing** — OncoKB and driver tiers are designed for somatic variants only; germline pathogenicity is distinct
5. **Privacy considerations** — some public cBioPortal instances may exclude germline variants due to sensitivity

---

## Future Support: No Explicit Guidance Available

The germline guide does **not** outline future plans or roadmap. cBioPortal's approach appears to be:
- **Present but not front-and-center:** germline support exists as a byproduct of storing raw variant data, not as a primary feature
- **Study-dependent:** germline inclusion depends on what each study uploaded, not platform-wide infrastructure

---

## Comparison to Alternatives

cBioPortal is **not** designed as a primary germline variant database. For germline-focused work, specialized alternatives are more appropriate:

| Tool | Germline Focus | Key Advantage |
|------|---|---|
| **ClinVar** | Yes (primary) | Gold standard for germline pathogenicity & ACMG classifications |
| **gnomAD** | Yes (primary) | Population frequency; loss-of-function metrics |
| **BRCA Exchange** | Yes (specific) | Deep curation for hereditary cancer genes (BRCA1/2) |
| **cBioPortal** | Partial (somatic-first) | Excellent for connecting germline variants to tumor clinical outcomes in indexed studies |
| **Ensembl/VEP** | No (annotation only) | Functional prediction; can be paired with any database |

---

## Recommendation

- **For germline classification & pathway analysis:** Use **ClinVar**, **gnomAD**, **ACMG guidelines**
- **For germline frequency in specific cancer cohorts:** Query **cBioPortal**, but verify the study includes germline data first
- **For germline-somatic correlations** (e.g., "Do patients with this germline variant develop different tumor mutational burdens?"): **cBioPortal** + clinical data join is ideal

Would you like me to check which cBioPortal studies actually contain germline variants, or help you query a specific gene in a known cohort?