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Cancer genetics: the importance of obtaining a family history

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VOL: 102, ISSUE: 40, PAGE NO: 28

Elizabeth Bancroft, BSc, MMedSci, RGN, is research nurse in cancer genetics, cancer genetics unit, Royal Marsden Hospital

Audrey Ardern-Jones, MSc, DipN (Lond) Genetics Cert, RGN, is clinical nurse specialist in cancer genetics, at Royal Marsden Hospital; Ella Lynch, BSc, Grad Dip Gen Couns, is genetic counsellor, Royal Melbourne Hospital, Melbourne, Australia

As new cancer predisposition genes continue to be identified, cancer genetics is becoming an integral part of the c...

As new cancer predisposition genes continue to be identified, cancer genetics is becoming an integral part of the cancer care pathway. Traditionally, little genetics has been taught to nursing students and asking a patient about her or his family history is still not a routine part of the nursing assessment in many healthcare sectors (Burke and Kirk, 2006; Skirton and Patch, 2000). The Department of Health's white paper Our Inheritance, Our Future (DH, 2003) emphasises the importance of education for health professionals, seeing this as a vital component for effectively translating advances in genetics into practice. The NHS Genetics Education and Development Centre has been established to facilitate the integration of genetics into nursing curricula and has developed core competencies for nurses to achieve at the point of registration (www.geneticseducation.nhs.uk).

Only a small proportion, approximately 5-10% of all cancers, are due to an inherited predisposition (Eeles et al, 2004). Most people with a family history of cancer will not be considered to be at high risk. However, several cancer-causing genes have been identified and NHS funded genetic testing is available for families where there is a high risk that a gene fault may be present.

Such families are rare but the presence of a genetic alteration has serious implications for all family members who may have inherited the faulty gene and face living with a greatly increased risk of developing cancer.

Cancer - a genetic disease

Most cancer is not hereditary but cancer is a genetic disease. The genetic information (DNA) in the cell is regularly damaged by environmental agents and by errors that can occur when cells undergo division during cell reproduction. In most cancers these errors (or mutations) accumulate during the lifetime, however, in inherited cancer a person is born with a mutation already present causing them to be at an increased risk of cancer.

The cancer-causing genes most often implicated in inherited cancers are tumour suppressor genes. The normal role of a tumour suppressor gene is to control the rate at which cells multiply.

For uncontrolled cell growth or tumour growth to occur, a mutation must occur in both copies of the tumour suppressor gene. This is the case in both sporadic cancers and inherited cancers.

When a person carries a genetic mutation this mutation is carried in the DNA of every single cell in the body, and on average half the germline cells - the ova and sperm cells. Therefore, there is the chance that the mutation can be passed on from generation to generation.

Most cancer predisposition genes are transmitted in an autosomal dominant fashion. This is evident when taking a family tree as you will tend to see successive generations of individuals affected with cancer on the same side of the family. A person who carries such a gene will have one altered copy and one working copy. One copy of each gene is passed on to each child and so this means that a person who carries a mutation can either pass on the working copy or the altered copy. Therefore, each child has a 50% chance of inheriting the altered copy of the gene.

How to take a family history

Nurses are ideally placed to identify families that may have an inherited predisposition to cancer and who may benefit from a referral to a genetics unit. They have direct patient contact and regularly discuss all aspects of a patient's life. Making an assessment and taking a brief family history can easily become a part of routine assessment.

Asking a patient about her or his family history can be a difficult and emotional subject. Sensitive family issues can be difficult to discuss, for example non-paternity, consanguinity, miscarriage, adoption, divorce and recent bereavements. Families are complex and diverse and it is not uncommon for there to be no information known about an entire side of the family. It is important to broach these topics with sensitivity.

If you are concerned that a family may have more cancer than would normally be expected it may be useful to draw a family tree. Family trees or pedigrees are diagrams that display the relationship among family members by using a combination of symbols and lines. Guidelines about how to draw a family tree can be found at: www.clingensoc.org/Docs/Standards/CGSPedigree.pdf.

Referral to a genetics unit

The main factors that may influence a decision to refer for a genetic assessment are:l Young age of onset, for example breast cancer under 40 years, bowel cancer under 50 years;

- Autosomal dominant pattern of inheritance, for example successive generations affected;

- Multiple cases of cancer in one individual;

- The occurrence of more than one rare tumour in a family, for example sarcomas, brain tumours;

- The occurrence of the same cancer or cancers known to be related, for example breast and ovarian, bowel and uterine;

- Ashkenazi Jewish ancestry in a family with multiple cases of breast and/or ovarian cancer.

What happens in an appointment at a cancer genetics clinic?

Families are often reviewed in a multidisciplinary meeting. Before a face-to-face appointment referred patients are often sent a family history questionnaire and, where appropriate, confirmation of the cancers in the family is undertaken. The ideal arrangement is for patients to be telephoned by a genetic/nurse counsellor before attending a clinic as patients may be requested to obtain a relative's death certificate or approach living relatives with cancer for consent so that the genetics team can access their medical records.

But it is not always possible to gather complete information, especially in the UK, which has a diverse range of cultures and changing family structures.

The patient is normally seen first by the genetic nurse/counsellor. The family history is reviewed with the patient and the risk of there being a genetic susceptibility to developing cancer is discussed. Issues around genetic testing may be raised if appropriate and screening for the patient themselves and other at-risk family members is discussed. It is important for the genetic/nurse counsellor to explore psychological issues as often individuals require support for bereavement and cancer anxiety. Further referral for ongoing counselling may be needed (Schneider, 2002).

If there are medical issues, such as the patient wishing to discuss prophylactic surgery, the patient should ideally be seen in a clinic where doctors are available to discuss medical management and counsellors are available to support patients.

Genetic Testing

Genetic testing is offered only in families where there is a high risk of identifying a genetic mutation.

In most cases a living affected family member needs to be offered the test first in order to identify the family specific mutation. This is because many different mutations can occur in the genes. However, when a mutation is detected, it is specific to a family. This is done by collecting a blood sample from the affected person and is called 'diagnostic mutation detection'. The process of finding the mutation in a family can take many months and testing at the regional genetics laboratory is not normally urgent.

With new techniques speeding up the process this may well change in line with NICE guidelines (NICE, 2004). If no mutation is detected in a high-risk family, this is considered uninformative as not all mutations can currently be detected in the known genes and also there are as-yet unidentified genes involved in hereditary cancer.

If a cancer-causing (pathogenic) mutation is detected in an affected family member, other unaffected family members can be offered testing to find out whether they carry the gene mutation. This is called 'predictive testing' and takes less time as the mutation in the family is already known.

Counselling Issues

There are numerous counselling issues for patients seen in cancer genetics clinics. As well as providing information about genetics in a way that is easy for patients to understand, it is the role of the genetic nurse/counsellor to explore these complex and difficult issues. It is important to explore possible reactions to a positive or negative test result and to prepare for either result (Kirk and McDonald, 2004). Ongoing support is vital. Some genetics services organise support groups for patients and can also link up patients for one-on-one peer support. The trained genetic nurse/counsellor also needs to recognise her or his own limitations and where a referral to formal psychological support may be beneficial. This is an essential part of practice with a person who may have had a history of suicidal ideation.

Learning objectives

- Understand the importance of taking a cancer family history

- Know how to take an accurate family history

- Understand when to refer to a specialist genetics unit

- Detail the common cancer predisposition genes

Guided reflection

- Outline your place of work and why you were interested in this article

- Detail the last time you encountered a patient who may have been genetically predisposed to cancer

- Write about a piece of information in the article that could have helped in your care of that patient

- Explain how you intend to disseminate what you have learnt among your colleagues

This article has been double-blind peer-reviewed.

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