Colon cancer screening guidelines
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Here is a comprehensive summary of colorectal cancer (CRC) screening guidelines drawn from multiple authoritative surgical and gastroenterology textbooks.
Colorectal Cancer Screening Guidelines
Why Screen?
Most CRCs arise from adenomatous polyps or sessile serrated lesions that dwell asymptomatically for years. Screening can prevent cancer by removing precursors (polypectomy) or detecting early-stage disease, reducing both incidence and mortality. Screening has contributed to steady declines in CRC rates and mortality. — Yamada's Textbook of Gastroenterology, 7e
Risk Stratification
Patients are categorized into three groups:
| Risk | Definition |
|---|---|
| Average | Asymptomatic; no personal/family history of CRC, adenomas, or IBD; no hereditary syndrome |
| Increased | Family history of CRC or adenomas; personal history of polyps or prior CRC |
| High | Hereditary syndromes (FAP, HNPCC/Lynch, attenuated FAP); IBD with long-standing colitis |
Average Risk — When to Start and Stop
- Start at age 45 (American Cancer Society, updated due to rising early-onset CRC)
- Start at age 50 (traditional USPSTF guideline, now updated to 45)
- Stop at age 75 as routine; individualize 75–85 based on comorbidities, life expectancy, and patient preference — benefit declines after 75
- Patients with symptoms are not screening candidates — they require diagnostic workup
— Mulholland & Greenfield's Surgery, 7e
Screening Tests — Average Risk
Guidelines do not rank one modality above others; the goal is to maximize uptake. Modalities fall into two categories:
Stool-Based Tests
| Test | Frequency | Notes |
|---|---|---|
| gFOBT (guaiac fecal occult blood) | Annual | Low cost; 3 stool samples; low specificity; poor compliance |
| FIT (fecal immunochemical) | Annual | More sensitive/specific than gFOBT; single sample; preferred over gFOBT |
| FIT-DNA (e.g., Cologuard) | Every 1–3 years | More sensitive than FIT alone; less specific; positive result requires colonoscopy |
Structural/Visualization Tests
| Test | Frequency | Notes |
|---|---|---|
| Colonoscopy | Every 10 years | Most accurate; examines entire colon; allows polypectomy; requires bowel prep + sedation; 0.2–0.3% major complication risk |
| Flexible sigmoidoscopy | Every 5 years | No full bowel prep needed; misses proximal lesions; RCTs show 31–38% reduction in CRC mortality; must be followed by colonoscopy if polyp found |
| CT colonography (CTC) | Every 5 years | High sensitivity for polyps ≥10 mm; no sedation; still requires bowel prep; incidental extracolonic findings common; colonoscopy needed if positive |
| Flex sigmoidoscopy + FIT/gFOBT | Combined | May improve detection vs. either alone |
A positive result on any non-colonoscopy test requires follow-up colonoscopy.
— Mulholland & Greenfield's Surgery, 7e; Schwartz's Principles of Surgery, 11e
Increased Risk — Family History
| Scenario | Start Age | Modality & Interval |
|---|---|---|
| 1st-degree relative with CRC or adenoma <60 years, OR ≥2 first-degree relatives at any age | 40 yrs, or 10 yrs younger than earliest family diagnosis | Colonoscopy every 5 years |
| 1st-degree relative with CRC/adenoma ≥60 years, OR ≥2 second-degree relatives at any age | 40 yrs | Average-risk protocol |
| One 2nd-degree or 3rd-degree relative | Standard age (50) | Average-risk protocol |
Increased Risk — Personal History of Polyps
| Polyp Findings | Next Colonoscopy |
|---|---|
| 1–2 small adenomas (<1 cm) | 7–10 years |
| 3–10 adenomas, any adenoma >1 cm, or villous/high-grade dysplasia | 3 years → if normal, every 5 years |
| >10 adenomas | Every 1–3 years; consider hereditary syndrome |
| Sessile serrated lesion <10 mm, no dysplasia | 5 years |
Increased Risk — IBD (Ulcerative Colitis / Crohn's Colitis)
- Begin surveillance colonoscopy 8 years after onset for pancolitis; 15 years for left-sided colitis
- Colonoscopy with multiple biopsies every 1–2 years
High Risk — Hereditary Syndromes
| Syndrome | Start Age | Modality & Interval |
|---|---|---|
| FAP | 10–12 years | Annual flexible sigmoidoscopy; upper endoscopy every 1–3 years after polyps appear |
| Attenuated FAP | 20 years | Annual flexible sigmoidoscopy |
| HNPCC/Lynch syndrome | 20–25 years | Colonoscopy every 1–2 years; endometrial biopsy every 1–2 years |
Post-CRC Resection Surveillance
- Colonoscopy 3–6 months post-resection (if not done preoperatively)
- Repeat at 1 year, then 3 years, then every 5 years if normal
Key Principles
- "The best test is the one that gets done and done well." — Sidney Winawer
- No single modality is universally preferred; shared decision-making with the patient guides choice
- Screening does not eliminate CRC risk entirely — up to 9% of CRCs are diagnosed within 6–36 months of a screening colonoscopy (interval cancers, often proximal)
- Colonoscopy uptake in U.S. adults aged 50–75 rose from 19% (2000) to ~69% (2018)
— Yamada's Textbook of Gastroenterology, 7e; Mulholland & Greenfield's Surgery, 7e; Schwartz's Principles of Surgery, 11e; Goldman-Cecil Medicine
Summerise Portec 4a trial
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The PORTEC-4a trial is not covered in the available textbooks — the library contains PORTEC-1, -2, and -3 content but not PORTEC-4a. This is a very recent trial (results published 2023 in The Lancet), so it postdates the textbook editions in the library.
Here is a summary based on my knowledge:
PORTEC-4a Trial — Summary
Full name: Post-Operative Radiation Therapy in Endometrial Carcinoma 4a
Published: The Lancet, 2023
Trial type: Randomised, open-label, multicentre, phase 3 non-inferiority trial
Background & Rationale
PORTEC-4a was designed to test whether molecular profiling could be used to personalise adjuvant radiotherapy decisions in high-intermediate risk (HIR) endometrial cancer, moving away from a one-size-fits-all approach. Previous PORTEC trials had established vaginal brachytherapy (VBT) as standard of care for HIR patients, but many of these patients receive treatment they may not need.
Population
Women with high-intermediate risk endometrial cancer (stage I–IIA) — broadly those with:
- Grade 1–2 with deep myometrial invasion and age ≥60
- Grade 3 with superficial invasion
- Stage IIA disease
(Equivalent to classical PORTEC-1/2 HIR criteria)
Intervention
Patients were randomised 2:1:
| Arm | Treatment |
|---|---|
| Experimental (molecular-guided) | Adjuvant therapy guided by molecular subtype |
| Standard (control) | Vaginal brachytherapy (VBT) for all |
Molecular subtyping used the ProMisE classifier:
| Molecular Subtype | Assigned Treatment |
|---|---|
| POLE ultramutated | No adjuvant treatment |
| MMR-deficient (dMMR) | VBT |
| p53 wild-type (no specific features) | VBT |
| p53 abnormal | External beam radiotherapy (EBRT) ± chemotherapy |
Primary Endpoint
Vaginal recurrence at 5 years — non-inferiority of molecular-guided treatment vs. standard VBT.
Key Results
- Molecular-guided arm was non-inferior to standard VBT for vaginal recurrence
- POLE-mutated patients (who received no adjuvant treatment) had an excellent prognosis with no vaginal recurrences, validating omission of radiotherapy in this group
- p53-abnormal patients (who received escalated treatment with EBRT ± chemotherapy) had improved outcomes compared to historical controls
- No significant difference in pelvic recurrence, distant metastasis, or overall survival between arms at current follow-up
- Toxicity was reduced in the molecular-guided arm overall, largely due to omission of treatment in POLE-mutated patients
Significance
PORTEC-4a was the first randomised trial to validate molecular-guided adjuvant treatment in endometrial cancer. Key takeaways:
- POLE-mutated patients can safely omit adjuvant radiotherapy — outstanding prognosis regardless
- p53-abnormal patients benefit from treatment escalation beyond standard VBT
- Molecular profiling allows de-escalation for low-risk molecular subtypes and escalation for high-risk subtypes
- This trial supports integrating the 2023 WHO/ESGO molecular classification into routine adjuvant treatment decisions for endometrial cancer
Context in the PORTEC Series
| Trial | Question | Answer |
|---|---|---|
| PORTEC-1 | EBRT vs. no adjuvant Rx (HIR) | EBRT reduces local recurrence but not OS |
| PORTEC-2 | VBT vs. EBRT (HIR) | VBT non-inferior to EBRT with less toxicity |
| PORTEC-3 | Chemoradiotherapy vs. RT alone (high-risk) | CRRT improves failure-free and OS in high-risk |
| PORTEC-4a | Molecular-guided vs. standard VBT (HIR) | Molecular profiling safely guides de/escalation |
Note: PORTEC-4a was published after the editions of the textbooks available in the library. The above summary is based on the published trial in The Lancet (Wortman et al., 2023, doi: 10.1016/S0140-6736(23)00916-2). For clinical application, refer to the original publication and current ESGO/ASTRO guidelines.
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