The Cochrane Review 'Screening for reducing morbidity and mortality in malignant melanoma' has been recently updated. We talked to Cochrane author Karsten Juhl Jørgensen to learn what the latest evidence says and why it is important.
Can you tell us about this Cochrane Review?
We reviewed the evidence for the benefits and harms of screening for malignant melanoma (a type of skin cancer) compared with no screening. We included all types of screening (e.g. skin self‐examination, or examination by a health professional) of any person not suspected of having malignant melanoma, i.e. people with no known suspicious mole or lesion, irrespective of age or gender. Studies in people thought to have a high risk of developing malignant melanoma were included, but not those known to previously have had melanoma.
What does the evidence tell us about the current available evidence for screening?
We found two randomised trials that met our inclusion criteria, but no data on any important outcomes where reported. This means that we do not have sufficient evidence to determine the benefits and harms of screening for malignant melanoma. Both international and national health organisations such as WHO and the UK National Screening Committee have outlined specific criteria to implement screening programmes on a population level (UKNSC 2015; WHO 2008), underlining the importance of solid evidence for both benefits and harms. Current screening practices for melanoma do not live up to these required evidence standards.
Why is this such an important topic?
Malignant melanoma is a skin tumour, which can cause death by spreading to other parts of the body; the number of malignant melanomas is rising sharply, while the risk of dying from the disease has been virtually stable. Currently, Germany has a national skin cancer screening programme and many interest groups campaign for melanoma screening.
Screening has the potential to reduce deaths from melanoma through earlier detection. However, there are also potential harms from screening people without symptoms of melanoma, such as finding melanomas and other skin lesions that would not have caused symptoms if they had remained undetected (i.e. overdiagnosis), unnecessary surgery, and possible psychological stress. There is also the risk that healthcare resources and finances are not being utilised optimally and could provide greater benefits if allocated to other interventions with a stronger evidence base... It is therefore important to establish the evidence base for both benefits and harms of screening for melanoma.
What does this tell us about screening programmes in current use?
We do not know whether current screening initiatives for malignant melanoma results in any benefits, or whether such potential benefits are outweighed by the potential harms, or if it is reasonable in relation to the resources used. We do know that current screening programmes and campaigns do not fulfil established general criteria for screening.
What is needed to determine the benefits and harms of screening?
To determine the benefits and harms of screening for malignant melanoma, a rigorously conducted randomised trial is needed. As malignant melanoma is a comparatively uncommon cause of death, such a trial would need to be quite large to provide useful answers.
Since opportunistic screening is already widespread in many countries, a challenge to any trial would be to make sure that the control group is not subject to such screening (i.e. to avoid contamination of the control group), since this may dilute both potential benefits and potential harms of screening estimated from the trial. Apart from a potential effect on mortality from melanoma, other important outcomes to consider in future trials include less aggressive treatment, overdiagnosis, psychosocial consequences, and resource use.
Why is this important?
This review shows that adult general population screening for malignant melanoma is not supported or refuted by current evidence from randomised controlled trials and therefore does not fulfil well-established screening criteria. Yet screening for malignant melanoma is currently practised in many countries in a more or less organised form. This is problematic since data from randomised trials demonstrating that benefits outweigh harms is considered mandatory before the introduction of screening programmes for cancer (UKNSC 2015; WHO 2008). The case of screening for malignant melanoma reinforces the importance of this requirement. First, non‐randomised studies of the effects of screening may lead to seriously misleading results. Second, screening has important harms, such as overdiagnosis and overtreatment of malignant melanomas, and robust trials would need to be performed to quantify them and enable us to weigh them against the benefit. Third, the majority of people who take part in the screening programmes cannot benefit from screening as they will never develop the disease. Fourth, screening programmes have a high potential for opportunity costs (Harris 2014). Fifth, when offering screening, healthcare systems invite asymptomatic people to an intervention that they have not asked for, which leads to ethical considerations that differ from those in regular health care (Sackett 2002).