Screening for breast cancer

There are few areas in imaging specifically and medicine in general, fraught with more controversy than screening for breast cancer. Due to the emotive issues surrounding the diagnosis, the scientific literature on breast screening and its issues reaches the lay press quickly and is sometimes reproduced in non-scientific, often potentially inaccurate terms. 

Mammography is notAny screening examination, like any test in medicine, will have a perfect studyfalse negative and ita false positive rate. Mammography as a screening exam does not find all cancers in all women, and will in some cases be read as positive in women without cancer. But until a cure is found, thisNonetheless mammography is currently believed to the best universally available tool we have to find breast cancers reliably and reproducibly early in the disease process.

The rationale behind screening

The rationale behind screening for breast cancer is the universally accepted dictum that (all other factors being equal) earlier diagnosis results in increased survival. The smaller the cancer at the time of diagnosis, the better the 5 year survival of breast cancer.

In general, if a breast cancer is found at less than a 1 cm diameter, the 5 year survival is the same as the general population at large. Screening for breast cancer is often cost and risk effective, feasible and evidence-based.

Historical background 

The increased survival, however cost, risks and treatments available vary dramatically in breast cancer is due in part to earlier diagnosis but also markedly improved treatments. 

The previously used radical surgical therapies for breast cancer are now a thing ofdifferent populations around the past. Lymphoedema used to be a very significant, dreaded complication of mastectomy and is now a rare occurrence in clinical practiceglobe.

There are three stepsnecessary to prove that screening mammography is effective in breast cancer ⁷:

1. The test can find cancers when they are smaller than without the test: mammography has succeeded here without doubt. To such an extent that "overdiagnosis" is now a concern.

2. randomized, controlled trials must show a reduction in mortality: there is no argument here in the accepted medical literature. Seven trials have demonstrated this ^2,7.

3. when the test is introduced into the general population, the death rate declines: the number of deaths per thousand of the population. Screening mammography has reduced the death rate of women ^7,8.

OverdiagnosisHistorical background 

The definitioninitial literature support for screening came from the Two Counties Trial in Sweden. Follow up for the trial participants continues and the data support the continued use of overdiagnosisscreening to detect breast cancer at an early stage when the therapy is epidemiologicpotentially curative and cosmetically acceptable. The Two Counties trail and the subsequent Health Insurance Plan (HIP) study in New York showed a decrease in deaths from breast cancer in those aged 40-74 years. A direct result of the HIP study was that screening was introduced in the USA, although it is not pathologic i.eperformed universally on all relevant populations there.

Concepts of risks

As they pertain to screening and breast cancer, there is significant confusion among the general population and many professionals about the concepts of different risks (relative risk, absolute risk and attributable risks).

Most cases of breast cancer are understood to be sporadic. The prevalence of genetic mutations associated with breast cancer such as the BRCA1 and 2 genes varies by population. Although some studies look at the occurrence of breast cancer in people with first degree family history, this does not mean that all of these cases are genetic.

Controversies

• Age to begin screening: As a cancer wouldgeneral rule, biologically, cancers in younger women tend to grow faster and hence metastasize earlier. The lag period in the time before a lesion is picked up is therefore potentially shorter in women under 50 than in post menopausal women. Some of the cancers seen in screening in those over 50 were actually potentially diagnosable when the patient was under 50 years ⁹. Nonetheless, on a population basis, in certain contexts, specifically low resource settings, screening populations under 50 is not have been diagnosed duringrecommended ¹⁴.  Recommendations vary country by country and across different professional organizations within the same country.
• Age to stop screening: Although it is currently accepted that screening is not cost effective after a patient's lifetime if screening had not taken placecertain age, as life expectancy rises, the precise age for each population is currently a matter of ongoing research.
• Overdiagnosis: Unfortunately, there are currently no pathological or imaging features to distinguish the progressive cancers - with lethal potential - from the indolent cases.In general, much overdiagnosis will likely represent cases of low grade DCIS (ductal carcinoma in situ) and those cases of indolent IDC that on review were actually present on mammograms of years ago but have only now been diagnosed for whatever reason (as a general rule, the rate.Some cases of growth of an IDC can be an indication of how aggressive the tumour is).

  All radiologists have seen

  cancers like this: they have been there for years in an invariably elderly lady and they don'tthat are well followed without intervention do not seem to change much with time. Maybe we need to re-evaluate in terms of how we manage confirmed low grade DCIS or small slow growing indolent cancers in elderly patients with multiple comorbidities.they appear on radiological studies available at present. Some breast cancers will not be fatal. Indeed in some autopsy series, up to 2% of female autopsies have breast cancer. But the cancers that will not kill are not only those we find on screening; they also include large palpable cancers ¹⁰.