PTEN Germline Mutations in Patients Initially Tested for Other Hereditary Cancer Syndromes: Would Use of Risk Assessment Tools Reduce Genetic Testing? (hereditary ovarian/breast/lynch syndrome/APS)

Abstract

Purpose. PTEN Hamartoma Tumor syndrome (PHTS) includes patients with Cowden syndrome or other syndromes with germline mutation of the PTEN tumor suppressor gene. The risk for breast, colorectal, and endometrial cancer and polyposis is increased, creating clinical overlap with hereditary breast and ovarian cancer (HBOC), Lynch syndrome (LS), and adenomatous polyposis syndromes (APS). We reviewed our series of patients with PHTS to determine how often testing criteria for these syndromes were met and how often other-gene testing was ordered before testing PTEN.

Patients and Methods. Patients were prospectively recruited by relaxed International Cowden Consortium criteria or presence of known germline PTEN mutation. Mutations were identified by mutation scanning/multiplex ligation-dependent probe amplification analysis and confirmed by sequencing/quantitative polymerase chain reaction. Patients were excluded if they were adopted, were <18 years of age, or if they were diagnosed with Cowden syndrome before 1998. Standard risk-assessment models were applied to determine whether patients met HBOC testing criteria, LS-relevant Amsterdam II/Bethesda 2004 criteria, or had adenomatous polyps. Prior probability of PTEN mutation was estimated with the Cleveland Clinic PTEN risk calculator.

Results. Of 137 PTEN mutation-positive adult probands, 59 (43.1%) met testing criteria for HBOC or LS. Of these, 45 (32.8%) were first offered HBOC, LS, or APS testing. Of those who underwent APS testing, none of the six patients met criteria. Initial risk assessment by a genetics specialist was significantly associated with immediate PTEN testing in patients also meeting HBOC testing criteria. Using this PTEN risk assessment tool could have spared gene testing for 22 unlikely syndromes, at a total cost of $66,080.

Conclusion. PHTS is an important differential diagnosis for patients referred for HBOC, LS, or APS. Risk assessment tools may help focus genetic analysis and aid in the interpretation of multiplex testing.

Implications for Practice:

Whereas hereditary breast and ovarian cancer syndrome, Lynch syndrome, and familial adenomatous polyposis are some of the most common causes of hereditary cancer predisposition, other conditions with overlapping clinical spectra exist. Timely identification of the right syndrome is critical for patient management and testing at-risk relatives. When
multiple conditions are possible, risk assessment tools help clinicians judge which condition is mos tlikely, allowing genetic testing o proceed in a stepwise and cost-effective manner. Here we present a series of patients with germline mutations of PTEN, a gene causing predisposition to breast, uterine, colorectal, and other cancers as well as to gastrointestinal polyposis. Many patients were tested for another syndrome prior to PTEN testing. Had now-existent risk assessment tools been used, elevated PTEN mutation risk in these patients might have been recognized immediately, leading to health care savings and shortened time to diagnosis.
The article also discusses how the use of risk assessment tools will remain important as genetic testing shifts from a single gene to a multiplex approach.