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

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

GASTROENTEROLOGY 2000;119:1756 –1760 Genetic Counseling and Testing for Germline p16 Mutations in Two Pancreatic Cancer–Prone Families HENRY T. LYNCH...

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GASTROENTEROLOGY 2000;119:1756 –1760

Genetic Counseling and Testing for Germline p16 Mutations in Two Pancreatic Cancer–Prone Families HENRY T. LYNCH,* RANDALL E. BRAND,‡ JANE F. LYNCH,* RAMON M. FUSARO,*,‡ THOMAS C. SMYRK,§ MICHAEL GOGGINS,储 and SCOTT E. KERN¶ *Department of Preventive Medicine and Public Health, Creighton University School of Medicine, Omaha, Nebraska; ‡Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska; §Department of Pathology, Mayo Clinic, Rochester, Minnesota; and Departments of 储Pathology and ¶Oncology, Johns Hopkins Medical Institutions, Baltimore, Maryland

The mortality from pancreatic cancer coincides closely with its incidence, indicating a dismal outlook. Hereditary factors probably account for approximately 5%– 10% of the pancreatic cancer burden. The molecular genetic etiology of pancreatic cancer is only beginning to be identified. We describe our genetic counseling experience with 2 large families prone to pancreatic cancer– malignant melanoma in which p16 (CDKN2) germline mutations had been identified. Members of each family underwent intensive counseling before and at the time of disclosure of p16 germline mutation findings. Two non–cancer-affected siblings from each of the 2 families had p16 mutations identified in DNA from their peripheral blood lymphocytes. In each case, a parent affected with pancreatic cancer also harbored the p16 mutation identified in DNA from their respective tumor blocks. The sibling pairs stated that they would seriously consider prophylactic pancreatectomy if biomarkers or imaging findings suggested a precancerous state. Our experience highlights limited options for managing these families and emphasizes the need for better tools to diagnose pancreatic cancer at a curable stage.

pproximately 28,600 new cases of pancreatic cancer occurred in the United States in 1999, and only about 2%–3% of these patients will live 5 years.1 Globally, the rates projected for 1999 were 92,000 new cases and 90,000 deaths from pancreatic cancer.2 The estimated rate of hereditary contribution to pancreatic cancer is 5%–10% but probably is higher considering the incomplete penetrance of pancreatic cancer among the subset of carriers with p16,3–7 BRCA2,8 –13 hMSH2 or hMLH1,14 or LKB1/STK1115 germline mutations. The identification of an inherited mutation in the cyclindependent kinase inhibitor 2 (CDKN2) tumor-suppressor gene (p16) has been reported in several families with pancreatic cancer and melanoma.3,6,16,17 In addition, CDKN2 inactivation is found in virtually all pancreatic cancer,18 suggesting that this gene has an important role in the pathogenesis of sporadic pancreatic cancer. The

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diagnosis of pancreatic cancer, in which death frequently occurs within a year of onset of symptoms, is often terrifying, particularly when familial risk is perceived to be high. We describe our DNA-based (p16 germline mutation) genetic counseling experience with members of 2 pancreatic cancer–prone families with malignant melanoma and cutaneous signs consistent with the familial atypical multiple mole melanoma (FAMMM) syndrome. We emphasize the need to develop a more powerful screening test for such families.

Case Reports Families A and B (Figure 1) were referred to us by concerned family members. Genealogy and history of cancer data were derived from questionnaires completed by adult members of the families. Only 1 of the pancreatic cancer– affected individuals was living when the study, which was approved by the Creighton University Institutional Review Board, was initiated. DNA was obtained from tumor tissue blocks, leading to the identification of the p16 germline mutation. A family information session was provided to members of families A and B in the geographic locations where most of the family members resided. The natural history, genetics, and available surveillance and management programs, including endoscopic ultrasonography (EUS) for pancreatic cancer, were discussed, emphasizing our current limited knowledge. Family members were also advised about the limited knowledge about penetrance of the p16 germline mutation. They were advised that a negative finding of the p16 mutation might not exclude them from cancer risk. Meticulous cutaneous examinations for malignant melanoma were also performed. Abbreviations used in this paper: CDKN2, cyclin-dependent kinase inhibitor 2; ERCP, endoscopic retrograde cholangiopancreatography; EUS, endoscopic ultrasonography; FAMMM, familial atypical multiple mole melanoma. © 2000 by the American Gastroenterological Association 0016-5085/00/$10.00 doi:10.1053/gast.2000.20335

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Figure 1. Pedigrees of families A and B. (Illustration by Tami Richardson-Nelson.)

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Twenty-one individuals (1 of whom had pancreatic cancer and is now deceased) from family A and 26 family members from family B elected to be tested for the p16 mutation. DNA was obtained from whole blood, buffy coat preparations, or from cell lines using a Chelex resin method (Bio-Rad, Hercules, CA)19 or from paraffin-embedded tissue as previously described.20 Two siblings with pancreatic cancer had the p16 germline mutation in family A, and this same mutation was identified in 2 unaffected children of 1 of these siblings. In family B, a patient with pancreatic cancer and 2 of that individual’s cancer-free children harbored the p16 mutation. In family A, 4 of 23 individuals had the identical splice site mutation (AGgt3 ATgt at the donor site of intron 2, previously reported by Moskaluk et al.7). In family B, an insertion producing a frameshift (GCG3 GCGG at codon 26) was identified in 3 of 26 individuals (M.G. and S.E.K., unpublished data). When the results of the individual p16 germline mutation testing became available, education about pancreatic cancer and its p16 mutation implications was again provided at a family information session. Thirty-four of the 47 persons tested received their results, 11 did not, and 2 had died. A private interview was conducted with each individual before results of testing were revealed. Queries dealt with the following: (1) personal estimate of risk of inheriting the p16 mutation; (2) attitudes about and concerns for insurance discrimination; (3) receptiveness for prophylactic total pancreatectomy; and (4) reasons for seeking risk assessment. Their p16 mutation results were then disclosed, questions were answered, and follow-up screening recommendations were discussed.

Genetic Counseling Findings Insurance discrimination. Seventy-four percent of the persons counseled were concerned about insurance discrimination and did not want DNA results sent to their physicians but wished to discuss the findings personally and requested that none of the findings be entered into their medical records. Genetic risk estimation. Before receiving their results, even though they were counseled that they had a 50% chance of inheriting the deleterious p16 mutation, 35% of the individuals estimated that their risk would be 50%; 6% underestimated their 50% risk, while 58% overestimated their risk. Reasons for seeking risk assessment. Reasons patients gave for seeking risk assessment were the potential benefit to their children/family (51%), future health management (48%), curiosity (16%), and other concerns (12%). These percentages total more than 100% because some patients expressed more than one reason for seeking risk assessment. Prophylactic pancreatectomy. Twenty-seven individuals (79% of those queried) stated, before receiving their negative results, that they would consider the option of prophylactic pancreatectomy. Only one individual strongly refused to consider this option under any circumstance. After receiving their results, the 4 cancer-free p16 mutation carriers felt strongly that prophylactic pancreatectomy would be an appropriate option, particularly if any of the biomarker studies

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and/or imaging findings, or our recommendations, supported prophylactic pancreatectomy.

Discussion Historically, pancreatic cancer in concert with malignant melanoma in a family was reported by Lynch and Krush in 1968.21 Skin lesions now known to be consonant with the FAMMM syndrome were subsequently observed in this family.22 In 1990, Bergman et al.23 reported clinical evidence of the integral association of pancreatic cancer and cutaneous malignant melanoma in a subset of families with FAMMM. Carcinoma of the pancreas has been found to segregate in a variety of hereditary cancer syndromes.24 Studies of extended multiple-case pancreatic cancer–prone families have repeatedly identified a pattern suggesting autosomal dominant inherited transmission25–27; in some, corroboration has been established at the molecular genetic level.28 –30 Recently, Silverman et al.31 reported a large population-based case-control study of cancer of the pancreas in 3 areas of the United States. They found that a family history of any cancer among first-degree relatives gave a significant (30%) increased risk of pancreatic cancer. There was a 3-fold increased risk (odds ratio, 3.2; 95% confidence interval, 1.8 –5.6) associated with a family history of pancreatic cancer. These findings are in accord with those of earlier studies by Ghadirian et al.32 and Falk et al.33 The importance of p16 mutations was observed by Goldstein et al.,6 who reported that 10 of 19 melanomaprone families had a p16 mutation. The kindreds were followed up prospectively for 6 –18 years. During this period, 2 individuals from families with a p16 mutation developed pancreatic cancer; thus the risk of carcinoma of the pancreas was increased by a factor of 13. No cases of pancreatic cancer were seen in the families without the p16 germline mutation. Data on lifetime risk of pancreatic cancer for carriers of p16 or BRCA2 mutations, and knowledge of other genetic mutations modifying risk among familial pancreatic cancer patients, are severely limited and are likely to vary with the specific germline mutation. Additionally, it remains to be proven that the detection of pancreatic cancer at either a dysplastic or carcinoma in situ stage will prolong an individual’s life expectancy. Brentnall et al.34 examined and performed prophylactic pancreatectomy on 7 of 14 high-familial-risk patients from 3 families who were believed to have manifested dysplasia of the pancreas on the basis of clinical history coupled with subtle abnormalities on EUS and endoscopic retrograde cholangiopancreatography (ERCP).

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They recommend EUS as the primary screening tool because EUS is less invasive than ERCP and detected every patient who had a positive finding on ERCP for dysplasia. These investigators note that there has been a virtual absence of prospective studies to detect precancerous lesions in the pancreas. There are also limited data on counseling individuals with germline p16 mutations. Bergman and Gruis35 raise the vexing question of how to counsel and manage families with p16 mutations, considering the inability to detect pancreatic carcinomas at an early stage. Whelan et al.,36 in response to the Bergman and Gruis study,35 expressed concern about the management of kindreds with the p16 mutation because the penetrance of pancreatic cancer had not been established. Also, the efficacy of screening for the early diagnosis of pancreatic cancer remains unproven. We now face this dilemma in 4 healthy individuals from these 2 kindreds. We told family members who harbor the p16 germline mutation that their lifetime risk for pancreatic cancer will significantly exceed that for individuals in the general population, but the true magnitude of this risk remains elusive. In turn, those who were negative for the mutation were told that their risk for pancreatic cancer would be less than for those carrying the mutation, but that it is uncertain whether their risk is reduced to that of individuals in the general population. After disclosure of results, many members of the family who tested negative for the p16 mutation believed that other factors may be involved in the incidence of cancer within their family and thought that their cancer risk persisted. Some family members took more comfort than others from receiving a negative result; some stated that it was better to remain pessimistic than to have false hope. During counseling, we advised participants of the need for surveillance for both pancreatic cancer and malignant melanoma and emphasized the limitations of screening for pancreatic cancer. This fact may have influenced attitudes about prophylactic pancreatectomy. With the present lack of data, we are recommending that carriers undergo surveillance with EUS at age 40 or younger, depending on the age distribution of pancreatic cancer affecteds in the family. We also suggest surveillance, albeit less aggressive, for individuals who are found to be negative for the p16 germline mutation because we cannot be confident that they are not at an increased risk for the development of pancreatic cancer. Ideally, such studies should be done in a research setting so that outcomes can be analyzed. We were impressed that family members would give serious consideration to prophylactic pancreatectomy,

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particularly if we recommended it and if it was based on our research findings. This response was undoubtedly influenced by the fact that they had seen their close relatives who were affected with pancreatic cancer invariably die, often within a year of diagnosis. We had carefully outlined to them all of the sequelae that could accompany a prophylactic total pancreatectomy, including the surgical mortality, which is about 1%–5%, and morbidity. Our experience highlights difficulties with genetic counseling that will be important for many years. Despite knowing the mutant gene, predicting risk in an individual patient/family is difficult, especially for germline mutations that are not very common and for which there are limited data. Other disciplines will still be needed to provide advances in treatment and screening to yield a major impact on genetic morbidity.37

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Received August 27, 1999. Accepted July 5, 2000. Address requests for reprints to: Henry T. Lynch, M.D., Department of Preventive Medicine and Public Health, Creighton University School of Medicine, 2500 California Plaza, Omaha, Nebraska 68178. e-mail: [email protected]; fax: (402) 280-1734. Supported by revenue from Nebraska cigarette taxes awarded to Creighton University by the Nebraska Department of Health and Human Services. The contents of this report are solely the responsibility of the authors and do not necessarily represent the official views of the State of Nebraska or the Nebraska Department of Health and Human Services. Funding was also provided by the National Institutes of Health through SPORE in Pancreatic Cancer CA95-21 (to R.E.B.) and SPORE in Gastrointestinal Cancer CA62924 (to S.E.K.). The authors thank Christine R. Kapler, B.S.N., Lavonne Fusaro, and Trudy G. Shaw, M.A., for technical support.