| Domain/phenotype | Current evidence level | Quantitative finding | Practical implication | Key source/date/DOI or PMID |
|---|---|---|---|---|
| Female breast cancer | **Established; moderate penetrance** | Average lifetime risk ≈25%, with an estimated **15%–40%** range after accounting for variant type, family history, and modifiers; truncating variants: OR **3.25** (95% CI 2.55–4.13); c.1100delC: OR **2.88** (2.65–3.22) (pqac-00000002, pqac-00000009) | Use individualized absolute-risk assessment rather than the gene result alone; enhanced breast surveillance is often appropriate for truncating-variant carriers. | Hanson et al., Oct 2023, DOI: [10.1016/j.gim.2023.100870](https://doi.org/10.1016/j.gim.2023.100870); Stolarova et al., Dec 2020, DOI: [10.3390/cells9122675](https://doi.org/10.3390/cells9122675) |
| Contralateral breast cancer | **Established increased risk** | CARRIERS: HR **2.0** (95% CI 1.0–4.2); 10-year cumulative incidence **13% premenopausal** and **4% postmenopausal**. BRIDGES protein-truncating variants: HR **2.25** (1.55–3.27) (pqac-00000010) | Discuss intensified surveillance and individualized surgical risk reduction; contralateral mastectomy is **not routinely indicated** solely because of CHEK2. | Yadav et al., Mar 2023, DOI: [10.1200/JCO.22.01239](https://doi.org/10.1200/JCO.22.01239); Hanson et al., Oct 2023, DOI above |
| Male breast cancer | **Probable association, but absolute risk poorly quantified** | CHEK2 is enriched among male breast-cancer predisposition findings, but available evidence does not provide a reliable variant-specific lifetime-risk estimate (pqac-00000013) | No CHEK2-specific population screening standard for unaffected men; management should be driven by personal and family history and breast symptoms. | Hanson et al., Oct 2023, DOI: [10.1016/j.gim.2023.100870](https://doi.org/10.1016/j.gim.2023.100870) |
| Prostate cancer | **Established association; moderate/variable penetrance** | Truncating variants are associated with increased prostate-cancer risk, but estimates vary by variant and ancestry; the reviewed evidence does not support one universal absolute-risk figure (pqac-00000003, pqac-00000010) | Consider PSA-based surveillance through shared decision-making, particularly with a prostate-cancer family history; counsel that evidence is less precise than for female breast cancer. | Hanson et al., Oct 2023, DOI above; Stolarova et al., Dec 2020, DOI above |
| Colorectal cancer | **Current evidence insufficient for a clinically important increase** | Recent cohorts of more than 6,000 heterozygotes found approximately null association (**OR ≈1.10**) for truncating or missense variants; earlier reports were inconsistent (pqac-00000004) | **2024 NCCN update de-implemented CHEK2-only intensified colon screening**; use general-population screening unless personal or family history independently warrants earlier colonoscopy. | Hodan et al., Dec 2024, DOI: [10.6004/jnccn.2024.0061](https://doi.org/10.6004/jnccn.2024.0061) |
| Thyroid, kidney, pancreatic, melanoma, testicular and hematologic cancers | **Limited, conflicting, or population/variant-specific** | Associations have been reported, but effect sizes are heterogeneous and often derive from founder populations or selected cohorts; testicular germ-cell tumor studies reported LOF OR **3.87** (1.65–8.86), requiring broader validation (pqac-00000004, pqac-00000008) | Do not institute organ-specific surveillance solely from CHEK2 status outside research; manage according to symptoms, family history, and standard risk factors. | AlDubayan et al., Apr 2019, DOI: [10.1001/jamaoncol.2018.6477](https://doi.org/10.1001/jamaoncol.2018.6477); Ozdemir et al., Nov 2024, DOI: [10.3390/cancers16223876](https://doi.org/10.3390/cancers16223876) |
| Variant-specific effects | **Established heterogeneity** | c.1100delC and other truncating variants generally confer moderate risk; p.Ile157Thr has lower breast-cancer effect, OR ≈**1.35–1.5**, mainly ER-positive; p.Ser428Phe and many missense variants have low or uncertain actionability (pqac-00000001, pqac-00000002, pqac-00000011) | Do not apply truncating-variant risk estimates to every missense variant. A VUS is nondiagnostic and must not guide surveillance or prophylactic surgery. | Hanson et al., Oct 2023, DOI above; Stolarova et al., Dec 2020, DOI above |
| Breast surveillance and prevention | **Guideline-supported, risk-adapted** | Modeling suggests annual MRI from **age 30–35**, adding annual mammography at **age 40**, may reduce breast-cancer mortality by **>50%** in women with CHEK2 pathogenic variants (pqac-00000009) | Calculate personalized risk, ideally with CanRisk or an equivalent model. Risk-reducing mastectomy is optional only after shared decision-making; salpingo-oophorectomy is not indicated solely for CHEK2. | Hanson et al., Oct 2023, DOI: [10.1016/j.gim.2023.100870](https://doi.org/10.1016/j.gim.2023.100870) |
| CHEK2-directed targeted therapy | **Not established** | No validated response rate or predictive biomarker supports treatment selection from germline CHEK2 status alone; ACMG states that no specific targeted medical treatment is currently recommended (pqac-00000009, pqac-00000012) | Treat the diagnosed cancer according to tumor type, stage, receptor status, and validated somatic biomarkers. PARP inhibitors or other DDR agents should not be used solely because of CHEK2 outside an approved tumor indication or clinical trial. | Hanson et al., Oct 2023, DOI above; TBCRC 048, PMID: [33119476](https://pubmed.ncbi.nlm.nih.gov/33119476/) |


*Table: Evidence-calibrated summary of established and uncertain CHEK2-associated cancer risks, variant effects, surveillance, and therapeutic implications. Quantitative estimates should be interpreted in the context of variant class, ancestry, family history, and other modifiers.*