What are the benefits of breast cancer screening?

Screening is estimated to save 10,000 lives each year. In 2017/18, around 2.5 million women aged 50-70 were invited for breast screening and about 18,000 cancers were detected.

‍

What are the negatives of breast cancer screening?

The hard reality is that detection of breast cancer doesn’t always result in lives being saved. There are several negatives implicated with screening. First of all, screening will turn people who test ‘positive’ into patients. This can have detrimental psychological effects on the patient. Therefore, it is ideal that the doctor has conclusive evidence that screening can alter the natural history of the disease (which is usually the case for breast cancer) ie. through effective treatment programs. Having said that, it is just not always possible for the doctor to know beforehand whether the screening will have any benefit, for example, if the patient is found to have late-stage breast cancer then treatment may not be possible. The difficulty, in this case, is that the doctor isn’t to know this before screening and has to disclose the results of screening regardless. Another thing to bear in mind is false-positive results and the unnecessary anxiety these bring.

‍

Why should data from screening programs be viewed with caution?

Screening programmes can lead to lead time bias and length time bias. Lead time bias is when early diagnosis falsely appears to prolong survival and so screened patients appear to live longer, but only because they were diagnosed earlier. Patients live the same length of time, but longer knowing they have the disease. Length time bias is the idea that diseases that are detectable through screening are more likely to have a favourable prognosis and may have never caused a problem in the first place, leading to the false conclusion that screening is beneficial in lengthening the lives of those found positive.

‍

What is the Inverse Care Law and how does it apply to this situation?

The Inverse Care Law describes a perverse relationship between the need for healthcare and its actual utilisation. This means that the quality of healthcare is poorer in the places that need it the most i.e. areas that have the most need for GPs will have longer waiting times etc, thus making their overall health situation worse. In this situation with increased waiting times for breast cancer screening, we may be able to suggest that the Inverse Care Law applies here as well. Moreover, perhaps, just like waiting times for breast cancer referrals are long, maybe waiting times for other appointments are also longer than they should be, thus highlighting a healthcare concern for the people living at the Isle of Man.

‍

1. Mrs Wright has been asked to attend her first routine breast screening, however, she has a few questions and concerns, and therefore comes to you as her GP. Her questions are as follows:

                (a) “Will the mammogram test really find breast cancer if I do have it?”

                (b) “If I don't have cancer, will I definitely get a negative result?”

               (c) “Say the mammogram is positive - does that definitely mean I have breast cancer?”

               (d) “If the mammogram is negative, am I definitely in the clear?”

HINT: Research test specificity, sensitivity, Negative Predictive Value and Positive Predictive Value.

‍

Author: Sana Khan

Editor: Allegra Wisking