Suspected cancer: recognition and referral

Context

Cancer has an enormous impact, both in terms of the number of people affected by it and the individual impact it has on people with cancer and those close to them. More than 300,000 new cancers (excluding skin cancers) are diagnosed annually in the UK, across over 200 different cancer types. Each of these cancer types has different presenting features, though they sometimes overlap. Approximately one‑third of the population will develop a cancer in their lifetime. There is considerable variation in referral and testing for possible cancer, which cannot be fully explained by variation in the population.

The identification of people with possible cancer usually happens in primary care, because most people first present to a primary care clinician. Therefore, evidence from primary care should inform the identification process and was used as the basis for this guideline.

The recommendations were developed using a 'risk threshold', whereby if the risk of symptoms being caused by cancer is above a certain level, then action (investigation or referral) is warranted. The positive predictive value (PPV) was used to determine the threshold. In the previous guideline, a disparate range of percentage risks of cancer was used to form the recommendations. Few corresponded with a PPV of lower than 5%. The guideline development group (GDG) felt that, in order to improve diagnosis of cancer, a PPV threshold lower than 5% was preferable. Taking into account the financial and clinical costs of broadening the recommendations, the GDG agreed to use a 3% PPV threshold value to underpin the recommendations for suspected cancer pathway referrals and urgent direct access investigations, such as brain scanning or endoscopy. Certain exceptions to a 3% PPV threshold were agreed. Recommendations were made for children and young people at below the 3% PPV threshold, although no explicit threshold value was set. The threshold was not applied to recommendations relating to tests routinely available in primary care (including blood tests such as prostate‑specific antigen and imaging such as chest X‑ray), primary care tests that could be used in place of specialist referral, non‑urgent direct access tests and routine referrals for specialist opinion. Further information about the methods used to underpin the recommendations can be found in the full guideline.

It is well recognised that some risk factors increase the chance of a person developing cancer in the future, for example, increasing age and a family history of cancer. However, risk factors do not affect the way in which cancer presents. Of the risk factors that were reported in the evidence, only smoking (in lung cancer) and age were found to significantly influence the chance of symptoms being predictive of cancer. Therefore, these are included in the recommendations where relevant. For all other risk factors, the recommendations would be the same for people with possible symptoms of cancer, irrespective of whether they had a risk factor. However, an exception was made to include asbestos exposure in the recommendations because of the high relative risk of mesothelioma in people who have been exposed to asbestos.