Genetic counseling and testing for germline p16 mutations in two pancreatic cancer-prone families

Prevalence of BRCA2 and CDKN2a mutations in German familial pancreatic cancer families

Previous small scale studies reported that deleterious BRCA2 and CDKN2a germline mutations contribute to a subset of families with inherited pancreatic cancer. As the prevalence of those mutations in the setting of familial pancreatic cancer is still not well defined for the German population, we evaluated the presence of BRCA2 and CDKN2a germline mutations in a large cohort of familial pancreatic cancer (FPC) families from the German National Case Collection for Familial Pancreatic Cancer (FaPaCa). Fifty-six FPC families with at least two-first-degree relatives with confirmed pancreatic cancer that did not fulfill the criteria of other tumor predisposition syndromes, were analyzed for BRCA2 and CDKN2a germline mutations by DHPLC and/or direct sequencing. No deleterious CDKN2a mutations were identified in our families suggesting that CDKN2a mutations are unlikely to predispose PC in FPC families without melanoma. No deleterious BRCA2 mutations, but 6 unclassified variants, were detected in our FPC collection. Combining the prevalence of deleterious BRCA2 germline mutations from our previous separate study with the data from this study we were able to much more accurately estimate the BRCA2 carrier frequency for FPC families in the German population. A total of two mutations and 6 unclassified variants (mutation range: 2.8-11.4%) were thus identified in 70 German FPC families, indicating that the prevalence of BRCA2 mutations in the German FPC population is less frequent than previously reported.

Familial pancreatic cancer

Pancreatic cancer’s high mortality rate equates closely with its incidence, thereby showing the need for development of biomarkers of its increased risk and a better understanding of its genetics, so that high-risk patients can be better targeted for screening and early potential lifesaving diagnosis. Its phenotypic and genotypic heterogeneity is extensive and requires careful scrutiny of its pattern of cancer associations, such as malignant melanoma associated with pancreatic cancer, in the familial atypical multiple mole melanoma syndrome, due to the CDKN2A germline mutation. This review is designed to depict several of the hereditary pancreatic cancer syndromes with particular attention given to the clinical application of this knowledge into improved control of pancreatic cancer.

Selection criteria for genetic assessment of patients with familial melanoma

Approximately 5% to 10% of melanoma may be hereditary in nature, and about 2% of melanoma can be specifically attributed to pathogenic germline mutations in cyclin-dependent kinase inhibitor 2A (CDKN2A). To appropriately identify the small proportion of patients who benefit most from referral to a genetics specialist for consideration of genetic testing for CDKN2A, we have reviewed available published studies of CDKN2A mutation analysis in cohorts with invasive, cutaneous melanoma and found variability in the rate of CDKN2A mutations based on geography, ethnicity, and the type of study and eligibility criteria used. Except in regions of high melanoma incidence, such as Australia, we found higher rates of CDKN2A positivity in individuals with 3 or more primary invasive melanomas and/or families with at least one invasive melanoma and two or more other diagnoses of invasive melanoma and/or pancreatic cancer among first- or second-degree relatives on the same side of the family. The work summarized in this review should help identify individuals who are appropriate candidates for referral for genetic consultation and possible testing.

Hereditary pancreatic cancer: a clinical perspective

Pancreatic cancer is an extraordinarily deadly disease and is responsible for over 220,000 deaths worldwide each year. One of the greatest risk factors for developing pancreatic cancer is a positive family history. Hereditary pancreatitis patients have a greatly elevated pancreatic cancer risk and individuals with cystic fibrosis may rarely develop this cancer, but often at very young ages. Various genetically linked cancer syndromes have been associated with pancreatic cancer in mutation-positive family members. Finally, familial pancreatic cancer-defined as families with two or more first-degree relatives who have pancreatic cancer but do not have a known cancer syndrome-is a known entity whose disease-causing mutation remains unidentified. This article describes research to date on hereditary pancreatic cancer, addresses how best clinicians should recognise hereditary forms of pancreatic cancer and explains the emotional burden of discovering a potentially lethal mutation. Many controversies and unanswered questions in hereditary pancreatic cancer remain.

Pancreatic cancer: translating lessons from mouse models and hereditary syndromes

Pancreatic ductal adenocarcinoma is the overwhelmingly predominant form of pancreatic cancer and the second most common type of gastrointestinal cancer (behind colorectal cancer) in the United States. Recent exciting advances in two areas of pancreatic ductal adenocarcinoma (i.e., the development and characterization of genetically engineered mouse models and the dissection of the genetic basis of hereditary forms in families) have been illuminating. These preclinical models and clinical syndromes provide the first tangible basis for progress in screening and prevention in high-risk populations and in the development of molecular diagnostics and experimental therapeutics.

The recognition and surgical management of heritable lesions of the pancreas

Our knowledge regarding the inherited factors that lead to the development of lesions within the pancreas is clearly incomplete. This article addresses clinical issues in patients at moderate-to-high risk for pancreatic malignancy, with special emphasis on the recognition and diagnosis of known genetic syndromes. Using the current available information, the authors attempt to equip the practicing surgeon with critical information to increase clinical suspicion for heritable syndromes and inform specific surgical management. Additionally, this article is meant to encourage the practicing surgeon to participate in the genetic testing/screening, cancer surveillance, and prevention activities of patients who have heritable cancer syndromes and associated pancreatic lesions that require surgery.

Pancreatic cancer screening: state of the art

Pancreatic cancer is a devastating disease with a median survival of approximately 6 months after diagnosis. Many factors are associated with a worse outcome; examples include late diagnosis, low resection rate, aggressive tumor behavior and a lack of an effective chemotherapy regimen. Owing to the low prevalence of pancreatic cancer relative to the diagnostic accuracy of present detection methods and the absence of promising treatment modalities, even in early stages, it is currently neither advisable nor cost effective to screen the general population. Efforts are focused on early screening of selected high-risk-cohorts, who account for approximately 10% of patients with pancreatic cancer. These include patients with chronic pancreatitis, individuals with a family history of pancreatic cancer, patients with hereditary pancreatitis, Peutz-Jeghers syndrome, cystic fibrosis or familial atypical multiple mole melanoma. At present, a multimodal-screening approach of endoscopic ultrasound, computed tomography and endoscopic retrograde cholangiopancreatography appears to be the most effective method to screen for pancreatic cancer in high-risk patients. Continued efforts are needed to elucidate effective testing to identify patients with nonhereditary risk factors who will benefit from screening protocols. A combined approach of serum markers, genetic markers and specific imaging studies may prove to be the future of pancreatic screening.

Familial pancreatic cancer: from genes to improved patient care

Pancreatic cancer is essentially a disease caused by inherited and acquired mutations in cancer-causing genes. A number of the genes responsible for the aggregation of pancreatic cancer in families have been discovered, including BRCA2, p16/CDKN2A, STK11 and PRSS1. Individuals can be tested for germline mutations in these genes; however, until recently, little could be done about the risk of pancreatic cancer if a patient was found to carry a mutation. Currently, new approaches are being developed to screen at-risk individuals for curable precancerous pancreatic lesions and laboratory studies have led to novel therapies that specifically target some of these genetic defects. This review focuses on the genetic basis for the familial aggregation of pancreatic cancer, with emphasis placed on the implications of the genetic alterations on clinical patient care.

Treatment of familial pancreatic cancer and its precursors

Approximately 10% of pancreatic cancers are believed to have a familial basis. The familial aggregation of pancreatic cancers provides a unique opportunity to prevent the development of pancreatic cancer, to identify and treat precancerous lesions of the pancreas, and to advance our understanding of the genetic basis for the development of all forms of pancreatic cancer. After appropriate genetic counseling, individuals with a strong family history of pancreatic cancer can now be tested for inherited genetic alterations that are known to increase the risk of pancreatic cancer. These include germline BRCA2, STK11/LKB1, p16/CDKN2A and PRSS1 gene mutations. Individuals with one of these inherited genetic alterations and individuals with a strong family history of pancreatic cancer can be counseled on smoking cessation and possible dietary modifications. Selected individuals, even if they are asymptomatic, can be screened using a combination of endoscopic ultrasound and multidetector computed tomography. Patients found to have a mass lesion in the pancreas would then be candidates for surgical resection. The resection of noninvasive precancers will cure these lesions before they have the opportunity to spread and metastasize. Even with the best early detection efforts, some patients will still be diagnosed with an invasive cancer. Surgical resection of invasive pancreatic cancer is proven to be safe and can provide long-term survival in patients with small, node-negative, and margin-negative cancers. Chemotherapy and radiation therapy are effective in some patients with invasive pancreatic cancer, but these therapies do not usually result in long-term cures. Individuals with a family history of pancreatic cancer may also choose to join a research study such as the National Familial Pancreas Tumor Registry.

Increased prevalence of the BRCA2 polymorphic stop codon K3326X among individuals with familial pancreatic cancer

Germline BRCA2 mutations predispose to the development of pancreatic cancer. A polymorphic stop codon in the coding region of BRCA2 (K3326X) has been described, and although an initial epidemiological study suggested it was not disease causing, subsequent studies have been inconclusive. To investigate the biological significance of the K3326X polymorphism, we determined its prevalence in patients with sporadic and familial pancreatic cancer. Using a case-control design, we studied 250 patients with resected sporadic pancreatic adenocarcinomas, 144 patients with familial pancreatic adenocarcinoma, 115 spouses of patients with pancreatic cancer, and a disease control group of 135 patients without a personal history of cancer who had undergone cholecystectomy for non-neoplastic disease. The K3326X polymorphism was detected using heteroduplex analysis and DNA sequencing. The BRCA2 K3326X polymorphism was significantly more prevalent in individuals with familial pancreatic cancer: 8/144 (5.6%) vs 3/250 controls (1.2%) (odds ratio, 4.84; 95% CI, 1.27-18.55, P<0.01). One K3326X carrier with familial pancreatic cancer carried an alteration (IVS 16-2A>G) suspected to be deleterious. Excluding this case did not alter the significance of the association (OR: 4.24, P<0.01). In contrast, there was no difference in prevalence among individuals with sporadic pancreatic cancer - 7/250 (OR: 2.37, 95% CI: 0.61-9.27). The increased prevalence of the BRCA2 K3326X polymorphism in patients with familial pancreatic cancer suggests that this polymorphism is deleterious and contributes to pancreatic cancer risk.

Cost-effectiveness of pancreatic cancer screening in familial pancreatic cancer kindreds

BACKGROUND

Endoscopic screening of families predisposed to pancreatic cancer is increasingly used, but the cost-effectiveness of screening is unknown.

METHODS

A decision analysis was used to compare one-time screening for pancreatic dysplasia with EUS to no screening in a hypothetical cohort of 100 members of familial pancreatic cancer kindreds. Abnormal EUS findings are confirmed with ERCP and patients with abnormal findings are candidates for total pancreatectomy. Lifetime medical care costs and life expectancy were modeled, and the main analysis was conducted from the third-party payer perspective. The base-case analysis assumed a 20% prevalence of pancreatic dysplasia and 90% sensitivity of EUS and ERCP.

RESULTS

Endoscopic screening was cost-effective, with an incremental cost-effectiveness ratio of $16,885/life-year saved. Screening was more cost-effective as the probability of dysplasia increased and as the sensitivity of EUS and ERCP increased. Screening remained cost-effective if the prevalence of dysplasia was greater than 16% or if the sensitivity of EUS was greater than 84%. Procedure costs had a limited impact on cost-effectiveness.

CONCLUSIONS

Endoscopic screening of carefully selected members of familial pancreatic cancer kindreds appears to increase patient life expectancy in a cost-effective manner. Screening should be performed in centers that have experience with endoscopic screening for pancreatic dysplasia. The cost-effectiveness of repeated screening remains to be determined.

CDKN2A germline mutations in familial pancreatic cancer

OBJECTIVE

To evaluate the prevalence of mutations in the CDKN2A gene encoding p16 and p14 in familial pancreatic cancer (FPC).

SUMMARY BACKGROUND DATA

The genetic basis of FPC is still widely unknown. Recently, it has been shown that germline mutations in the p16 tumor suppressor gene can predispose to pancreatic cancer. The presence of p14 germline mutations has yet not been determined in this setting.

METHODS

Eighteen families with at least two first-degree relatives with histologically confirmed pancreatic cancer and five families with at least one patient with pancreatic cancer and another first-degree relative with malignant melanoma of the German National Case Collection for Familial Pancreatic Cancer were analyzed for CDKN2A germline mutations including p16 and p14 by direct DNA sequencing. All participating family members were genetically counseled and evaluated by a three-generation pedigree.

RESULTS

None of 18 FPC families without malignant melanoma revealed p16 mutations, compared to 2 of 5 families with pancreatic cancer and melanoma. Truncating p16 germline mutations Q50X and E119X were identified in the affected patients of pancreatic cancer plus melanoma families. None of the 23 families revealed p14 germline mutations.

CONCLUSIONS

CDKN2A germline mutations are rare in FPC families. However, these data provide further evidence for a pancreatic cancer-melanoma syndrome associated with CDKN2A germline mutations affecting p16. Thus, all members of families with combined occurrence of pancreatic cancer and melanoma should be counseled and offered screening for p16 mutations to identify high-risk family members who should be enrolled in a clinical screening program.

Phenotypic variation in eight extended CDKN2A germline mutation familial atypical multiple mole melanoma-pancreatic carcinoma-prone families: the familial atypical mole melanoma-pancreatic carcinoma syndrome

BACKGROUND

Hereditary pancreatic carcinoma shows extant phenotypic and genotypic heterogeneity as evidenced by its integral association with a variety of hereditary cancer syndromes inclusive of the familial atypical multiple mole melanoma (FAMMM) syndrome in concert with CDKN2A (p16) germline mutations.

METHODS

Creighton University's familial pancreatic carcinoma resource comprises 159 families of which 19 (12%) show the FAMMM cutaneous phenotypes. The authors describe eight families with the FAMMM-pancreatic carcinoma (FAMMM-PC) association in concert with a CDKN2A germline mutation. Each family was thoroughly educated about all facets of the study, including the molecular genetics, reduced penetrance of CDKN2A mutations, and their variable expressivity. Genetic counseling was provided to each patient.

RESULTS

Diversity in cancer presentation within and among the families was noteworthy, wherein melanoma predominated in certain of the families whereas pancreatic carcinoma predominated in others. Early-onset pancreatic carcinoma (at ages 35, 45, 46, and 49 years) appeared in some of the families whereas markedly later-onset pancreatic carcinoma occurred in others. There were four incidences of melanoma and pancreatic carcinoma as double primaries in the same individuals. One patient with melanoma and pancreatic carcinoma had a third primary of breast carcinoma. Another patient had sarcoma, esophageal carcinoma, and two melanoma primaries, whereas his daughter had sarcoma and was a carrier of a CDKN2A mutation.

CONCLUSIONS

The authors suggest that these tumors may collectively, in concert with CDKN2A mutations, constitute a "new" putative hereditary carcinoma syndrome referred to as FAMMM-PC. More clinical and molecular genetic research on additional families with pancreatic carcinoma in concert with the FAMMM will be required.

Update on familial pancreatic cancer

Approximately 5% to 10% of patients with pancreatic cancer have one or more first-degree relatives with this disease. A subset of these individuals have a hereditary form of pancreatic cancer designated by association with such hereditary disorders as familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, hereditary pancreatitis, or familial atypical multiple mole melanoma (FAMMM) syndrome. A subset of those FAMMM kindred with the CDKN2A (p16) germline mutation that expresses both pancreatic cancer and malignant melanoma may constitute a new hereditary pancreatic cancer-prone syndrome.