GPs 'failing to prescribe tamoxifen to prevent breast cancer'

4:00pm Tuesday 14th February 2017

content supplied by NHS Choices

"Half of GPs unaware of drug's use [tamoxifen] in cancer prevention," The Guardian reports.

An online survey of GPs found many were unaware of national guidelines recommending the use of tamoxifen for at risk women.

Guidance produced by the National Institute for Health and Care Excellence (NICE) in 2013 recommends women thought to be at high risk of developing breast cancer because they have a family history of the condition should be given the option to take the hormone therapy tamoxifen.

This survey of more than 900 GPs found around half knew tamoxifen can reduce the risk of breast cancer in women who don't currently have cancer but have a high risk because of their family history.

A quarter knew guidelines recommend tamoxifen for those at high risk, and three quarters would be willing to prescribe it to women at high risk.

One important factor not discussed in detail in the media is that tamoxifen is unlicensed for breast cancer prevention. While GPs have the power to prescribe unlicensed drugs if they think they would benefit an individual patient, they are often reluctant to do so.

A commonly reported concern is GPs feel they would be more liable for criticism if a patient developed side effects or complications.

A lot of the numbers being reported by the media are guesswork. A small survey cannot prove half a million women are "missing out" on preventative treatment.

If you're concerned about your family history of breast cancer, the first step is to talk to your GP.

Where did the story come from?

The study was carried out by researchers from the University of Leeds, University College London, Queen Mary University London and the University of Leicester in the UK and Harvard University in the US.

It was funded by Cancer Research UK. The authors declared no conflicts of interest.

The study was published in the peer-reviewed British Journal of General Practice and is open access, meaning it's free to read online.

The story was covered by a number of UK media outlets. While the media accurately reported around half of GPs surveyed were unaware tamoxifen can reduce breast cancer risk, some of the reporting was rather misleading.

The Sun stated that, "500,000 women at higher risk of cancer denied 6p prevention pill because GPs aren't clued up on latest research", a claim echoed in The Daily Telegraph's headline, "Breast cancer pill denied to 500,000 women".

In fact, 500,000 is the approximate number of patients who could hypothetically benefit from the pill. But the study did not report how many women actually received or asked for the pill and were "denied" it. The survey only looked at GP's attitudes and knowledge, not their prescribing history.

This drug isn't licensed for preventative use, so it isn't that surprising GPs aren't prescribing it for this group of patients.

While useful at a population level, the fact tamoxifen is not especially effective at an individual level was not discussed.

As the study itself mentions, for every 42 women taking tamoxifen over the course of 10 years, only one case of breast cancer would be prevented. Or, in other words, the number needed to treat (NNT) for tamoxifen is 42.

What kind of research was this?

This was a cross-sectional survey of GPs practising in the UK in 2016, undertaken online. It aimed to find out GPs' attitudes to prescribing tamoxifen for primary prevention in women at risk of breast cancer.

2013 NICE guidelines on hereditary breast cancer suggest women meeting specific criteria with a high risk of breast cancer may be offered tamoxifen for primary prevention, before cancer has developed. Tamoxifen may also be considered for women with a moderate risk.

However, as NICE highlighted in 2013, tamoxifen was not licensed for primary prevention of breast cancer, and this situation hasn't changed.

As this was a survey of a sample of GPs, it cannot be said to be representative of the views of all GPs in the UK, but does give a good idea of attitudes generally.

What did the research involve?

Researchers approached 13,764 GPs from across the UK, of which 928 completed the survey.

Respondents from Scotland were excluded as they have an agreed care pathway in place for the prescription of tamoxifen.

GPs were randomised to one of four scenarios describing a hypothetical patient at increased risk of breast cancer.

The hypothetical patients were intended to be representative of a typical patient attending a family history clinic.

The scenarios involved a patient at either high lifetime risk (greater than 30% chance of breast cancer) or moderate risk (between 17% and 30% chance of breast cancer).

The GPs were told either they would need to write the first prescription and continue as the main prescriber, or a family history clinician had already written the first prescription and asked the GP to take over as the main prescriber.

They were provided with information about the current UK guidelines, the eligibility criteria for taking tamoxifen, the harms and benefits of the drug, and the typical patient pathway.

The GPs were asked questions around five areas:

The responses to the questionnaire were analysed, looking at the effect of cancer risk on the hypothetical patient and who was the initial prescriber (GP themselves or family history clinician).

What were the basic results?

Of the 928 GPs surveyed:

How did the researchers interpret the results?

The researchers concluded that, "Initiating tamoxifen prescriptions for preventive therapy in secondary care before asking GPs to continue the patient's care may overcome some prescribing barriers."

They added: "One of the major barriers to implementing the tamoxifen guidelines is the low awareness of its potential to be used as preventive therapy.

"Although cross-sectional surveys do not allow causal inferences, the data suggest increasing awareness of preventive medications could facilitate appropriate prescribing behaviour," they said.

The researchers advised that, "The most common sources of information were training days, GP magazines, and national guidelines. Strategies to promote awareness of tamoxifen for primary prevention should consider ways to target these sources."

Conclusion

This large survey shows around half of GPs surveyed were unaware of the benefits of tamoxifen: namely, that the drug can reduce the risk of breast cancer in women with a family history of the condition. Only around a quarter of GPs surveyed were aware of the current UK guidelines.

Researchers found GPs were more likely to feel comfortable carrying on a prescription initiated by hospital doctors, rather than being the one to take the decision to prescribe.

This is perhaps unsurprising given that the drug is still not licensed for the primary prevention of cancer. NICE currently recommends prescribers need to take full responsibility for their decision to prescribe tamoxifen, and obtain full informed patient consent. Many GPs may not feel sufficiently informed or comfortable about making these decisions themselves.

In light of this, the researchers' conclusions are therefore quite appropriate. They suggest the study indicates a need to provide GPs with information about the official guidelines, as well as benefits and support for GPs in prescribing tamoxifen.

This study does have some limitations, however:

If you're concerned about your family history of breast cancer, the first step is to talk to your GP.

You can also reduce your risk of breast cancer by taking regular exercise, eating a healthy diet, and achieving or maintaining a healthy weight.

Read more about preventing breast cancer.

Summary

"Half of GPs unaware of drug's use [tamoxifen] in cancer prevention," The Guardian reports. An online survey of GPs found many were unaware of national guidelines recommending the use of tamoxifen for at risk women.

Links to Headlines

Half of GPs unaware of drug's use in cancer prevention - study. The Guardian, February 14 2017

Breast cancer pill denied to 500,000 women. The Daily Telegraph, February 14 2017

Cancer pill denied to thousands of women: Doctors are failing to prescribe two daily pills that can slash odds of developing the disease. Daily Mail, February 14 2017

500,000 women at higher risk of cancer denied 6p prevention pill because GPs aren't clued up on latest research. The Sun, February 14 2017

GPs fail to offer women drugs that reduce breast cancer risk. The Times, February 14 2017 (subscription required)

Links to Science

Smith SG, Foy R, McGowan JA, et al. Prescribing tamoxifen in primary care for the prevention of breast cancer: a national online survey of GPs' attitudes. British Journal of General Practice. Published online February 13 2017

Useful Links

Further Readings

National Institute for Health and Care Excellence (NICE). Familial breast cancer: classification, care and managing breast cancer and related risks in people with a family history of breast cancer. Information for the public. Last updated August 2015

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