Adult Summary Report

Secondary Findings in Adult Subjects

Non-diagnostic, excludes newborn screening & prenatal testing/screening

• Status (Adult): Passed (Consensus scoring is Complete)
• Curation Status (Adult): Released 1.0.1
• GENE/GENE PANEL: SMAD4, BMPR1A
• Condition: Juvenile polyposis syndrome
• Mode(s) of Inheritance: Autosomal Dominant

Actionability Assertion

• SMAD4 ⇔ 174900: Assertion Pending
• SMAD4 ⇔ 175050: Assertion Pending
• BMPR1A ⇔ 174900: Assertion Pending

Actionability Rationale

This topic was initially scored prior to development of the process for making actionability assertions. The Actionability Working Group decided to defer making an assertion until after the topic could be reviewed through the update process.

Final Consensus Scores

Outcome / Intervention Pair	Severity	Likelihood	Effectiveness	Nature of the Intervention	Total Score
Gastrointestinal cancer / Endoscopic surveillance	2	3C	3E	2	10CE

1. What is the nature of the threat to health for an individual carrying a deleterious allele?

Prevalence of the Genetic Condition

Robust prevalence estimates for Juvenile polyposis syndrome (JPS) are not available because of its rarity, the lack of comprehensive clinical phenotype ascertainment and the fact that there are no population-based molecular studies. However, estimates of the population prevalence suggest the frequency of JPS may be similar to that of Peutz-Jeghers syndrome suggesting a frequency of around 1:50,000, although it may be as low as 1:120,000. [1]

Clinical Features

JPS is characterized by predisposition to hamartomatous polyps in the gastrointestinal tract, specifically in the stomach, small intestine, colon, and rectum. Histological differences and topographical distribution within the gastrointestinal tract serve to distinguish between JPS and Peutz-Jeghers Syndrome. The number of polyps in individuals with JPS varies, with dozens to many hundreds of polyps present in the fully developed syndrome.
A combined syndrome of JPS and hereditary hemorrhagic telangiectasia (HHT) (termed JPS/HHT) is present in most individuals with an SMAD4 pathogenic variant. [Hereditary hemorrhagic telangiectasia is addressed in a separate report] [1, 2, 3]

Natural History

The term 'juvenile' refers to the polyp type rather than to the age of onset, although most individuals with JPS have some polyps by 20 years of age. JPS usually manifests during childhood with polyps beginning to appear in the first decade of life. The average age at diagnosis is 18.5 years, but may be later, with rectal bleeding with anemia as the most common presenting symptom.


Most juvenile polyps are benign; however, malignant transformation can occur. In those who develop cancer, the mean age of colon cancer is 34 years, with a range of 15 to 68 years and the median age of upper GI cancer is 58 years with a range of 21 to 73 years. [1, 2, 3]

2. How effective are interventions for preventing harm?

Patient Management

To determine the extent of disease, a baseline evaluation of patients should include a clinical history, complete blood count, colonoscopy, and upper endoscopy. (Tier 3) [3]

Colectomy and ileorectal anastomosis or proctocolectomy and ileal pouch-anal anastomosis is indicated for polyp-related symptoms, or when the polyps cannot be managed endoscopically. One case series reported on long-term outcomes of colonic surgery in 13 patients presenting with symptomatic colon polyps (median age at diagnosis=10 years, range=1-50 years). Eight patients had their rectum removed during the study period; 5 had an ileal pouch-anal anastomosis, one had a Koch pouch as a restorative surgery, and 2 had an end ileostomy. No relation was observed between the number of colonic and rectal polyps and the type of surgery or the need for proctectomy. Patients were followed up a median of 3 years (range=2-24 years) after their ultimate operations. During this period, one patient (20%) who underwent restorative proctectomy and 4 patients (80%) whose rectums were preserved required multiple endoscopic polypectomies for recurrent polyps in the pouch (first patient) or their rectums (the other 4 patients). The patient who underwent the Koch procedure required surgery for recurrent polyps in her pouch. (Tier 2) [2]

Surveillance

Colonoscopy is recommended in patients with JPS. Recommended starting age ranges across guidelines from 12-18, while frequency ranges from annually to every 3 years. The frequency of screening may be determined by the findings of the previous endoscopy, and may be extended to longer intervals after age 35. There are no comparative studies to demonstrate the potential benefit of screening; however, there is substantial risk of CRC in JPS patients. The life-time risk of CRC death in JPS patients not undergoing surveillance is estimated to be as high as 1 in 6. One retrospective review of a registry of 44 patients with JPS undergoing routine surveillance (380 patient-years follow up) of the upper and lower GI tract has reported surveillance results. Screening detected 767 polyps and 20 adenomatous polyps. Five patients were identified requiring colorectal surgery. Two patients developed colorectal cancer while undergoing surveillance. However, given the lack of a control group it is unclear how many of these patients would have been detected clinically without undergoing surveillance. (Tier 2) [1, 2, 4, 5]

Upper endoscopy is also recommended in patients with JPS. Recommended starting age ranges across guidelines from 12-25 years, while frequency ranges from annually to every 3 years. The frequency of screening is determined by the findings of the previous endoscopy, and may be extended to longer intervals after age 35. The risk of gastric and duodenal cancer in JPS is around 15-21%. Among the retrospective registry of JPS patients, gastrodueodenal polyps were found in 37% of patients and two patients were identified with adenomatous polyps of the stomach. Two patients were identified requiring gastrectomy. One patient developed cancer while undergoing surveillance. However, given the lack of a control group it is unclear how many of these patients would have been detected clinically without undergoing surveillance. (Tier 2) [1, 2, 4, 5]

Periodic enteroscopy, capsule endoscopy and/or CT enterography may be used for surveillance of the small intestine. (Tier 2) [2, 4]

A case series of small-bowel capsule endoscopy of ten adults (median age 39.2 years) with documented JPS identified 2 patients that had small-bowel polyps beyond the range of standard gastroscopy identified at capsule endoscopy. Duodenal polyps were detected in a third patient at capsule endoscopy not previously detected by standard gastroscopy. However, given the lack of a control group it is unclear how many of these patients would have been detected clinically without undergoing surveillance. (Tier 5) [6]

Circumstances to Avoid

None identified.

3. What is the chance that this threat will materialize?

Mode of Inheritance

Autosomal Dominant

Prevalence of Genetic Variants

No estimates were identified for the prevalence of SMAD4 or BMPR1A mutations. Up to 60% of individuals with a clinically defined JPS are found to exhibit mutations of the SMAD4 or BMPR1A genes. (Tier 3) [2]

Penetrance

No studies have examined the proportion of individuals with known germline pathogenic variants for JPS who develop polyps. It is expected to be higher than 90%. (Tier 4) [3]

Estimates for the risk of colorectal cancer range from 10-68%, though a more recent synthesis estimates a range of 38-68%. (Tier 3) [1, 2, 3]

An estimated 21% of patients with JPS will develop upper gastrointestinal cancer. (Tier 3) [1, 2]

Relative Risk

The relative risk of developing colorectal cancer was found to be 34.0 (14.4 to 65.7). (Tier 3) [3]

Expressivity

The number of polyps in individuals with JPS varies. Some individuals may have only four or five polyps over their lifetime; others in the same family may have more than 100. (Tier 4) [3]

4. What is the Nature of the Intervention?

Nature of Intervention

Identified interventions include upper and lower gastrointestinal surveillance.

5. Would the underlying risk or condition escape detection prior to harm in the setting of recommended care?

Chance to Escape Clinical Detection

The average age at diagnosis is 18.5 years, but may be later, with rectal bleeding with anemia as the most common presenting symptom. (Tier 3) [2]

Date of Search: 12.18.2015

Reference List

1. Cairns SR, Scholefield JH, Steele RJ, Dunlop MG, Thomas HJ, Evans GD, Eaden JA, Rutter MD, Atkin WP, Saunders BP, Lucassen A, Jenkins P, Fairclough PD, Woodhouse CR. Guidelines for colorectal cancer screening and surveillance in moderate and high risk groups (update from 2002). Gut. (2010) 59(5):666-89.

2. Syngal S, Brand RE, Church JM, Giardiello FM, Hampel HL, Burt RW. ACG clinical guideline: Genetic testing and management of hereditary gastrointestinal cancer syndromes. Am J Gastroenterol. (2015) 110(2):223-62; quiz 263.

3. J Larsen Haidle, JR Howe. Juvenile Polyposis Syndrome. 2003 May 13 [Updated 2015 Dec 03]. In: RA Pagon, MP Adam, HH Ardinger, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from: http://www.ncbi.nlm.nih.gov/books/NBK1469

4. National Comprehensive Cancer Network,. Genetic/Familial High-Risk Assessment: Colorectal (version 3.2017). Other. (2017) Website: http://www.nccn.org/professionals/physician_gls/pdf/genetics_colon.pdf

5. Diagnosis and Management of Colorectal Cancer. SIGN. (2015) Website: http://www.sign.ac.uk/pdf/sign126.pdf

6. Postgate AJ, Will OC, Fraser CH, Fitzpatrick A, Phillips RK, Clark SK. Capsule endoscopy for the small bowel in juvenile polyposis syndrome: a case series. Endoscopy. (2009) 41(11):1001-4.