Which feature best distinguishes screening for colorectal cancer (FOBT/colonoscopy) from screening for prostate cancer (PSA) in terms of adherence to Wilson & Jungner screening criteria?

Explanation

## Screening Principles: Evidence of Efficacy & Harm-Benefit Balance **Key Point:** The **Wilson & Jungner criteria** (WHO, 1968) require that screening programs have **proven efficacy in reducing disease mortality** and that **benefits outweigh harms**. Colorectal cancer screening meets these criteria; prostate cancer screening does not. ### Colorectal Cancer Screening - **Proven mortality reduction**: FOBT reduces CRC mortality by **15–20%**; colonoscopy by **60–70%** (based on polyp removal) - **Clear natural history**: Adenoma → dysplasia → cancer over **10–15 years** (long detectable preclinical phase) - **Acceptable harm profile**: Colonoscopy has low perforation risk (~1 in 1000); FOBT has minimal harm - **Recommended**: WHO, USPSTF, NCCN all recommend CRC screening in average-risk adults aged 45–75 years ### Prostate Cancer Screening (PSA) - **Uncertain mortality benefit**: Multiple RCTs (PLCO, ERSPC) show **minimal or no mortality reduction** - **High false-positive rate**: PSA has sensitivity ~80% but specificity only ~25%; leads to **unnecessary biopsies** - **Overdiagnosis**: Many detected cancers are **indolent** and would never cause harm - **Significant harms**: Biopsy complications, anxiety, overtreatment with erectile dysfunction and incontinence - **Not recommended**: USPSTF recommends **against routine PSA screening** in asymptomatic men; shared decision-making only in 40–70 years ### Wilson & Jungner Criteria Comparison | Criterion | Colorectal Cancer | Prostate Cancer | |-----------|-------------------|------------------| | **Disease importance** | ✓ High mortality | ✓ High mortality | | **Natural history known** | ✓ Yes (adenoma sequence) | ✓ Yes | | **Detectable preclinical phase** | ✓ Yes (adenoma) | ✓ Yes (latent cancer) | | **Effective treatment available** | ✓ Yes (polypectomy, surgery) | ✓ Yes (surgery, radiation) | | **Screening test available** | ✓ Yes (FOBT, colonoscopy) | ✓ Yes (PSA, DRE) | | **Test acceptable to population** | ✓ Moderate (colonoscopy invasive) | ✓ Moderate (PSA simple) | | ****Proven mortality reduction** | ✓✓ **YES** | ✗ **NO** | | **Benefits > Harms** | ✓✓ **YES** | ✗ **NO** | **High-Yield:** The critical distinction is **evidence of mortality reduction** and **favorable harm-benefit ratio**. Colorectal cancer screening has both; prostate cancer screening has neither. **Mnemonic:** **SCREENED** = Serious disease, Cure available, Recognizable early, Evidence of benefit, Effective test, Natural history known, Detectable phase - Colorectal cancer: ✓ All criteria met - Prostate cancer: ✗ Fails on "Evidence of benefit" and "Effective test" (high false-positive rate) **Clinical Pearl:** The **USPSTF Grade D recommendation** (against routine PSA screening) reflects the lack of mortality benefit and excess harms. In contrast, **USPSTF Grade A recommendation** for CRC screening reflects strong evidence of mortality reduction. **Warning:** Do not confuse "test availability" with "screening efficacy." PSA is available and simple, but screening does not reduce mortality and causes significant overdiagnosis and overtreatment. [cite:Park 26e Ch 10]