Breast cancer is the most common cancer in women in the UK and is currently the second leading cause of cancer deaths after lung cancer1. In 1988, the National Health Service Breast Screening Programme (NHSBSP) was introduced in the UK with an aim to detect small invasive cancers as well as pre-invasive cancers to reduce mortality from the disease2. Despite being well received generally and have progressed over the years with positive outcomes2,3, the NHSBSP is not without opposition and has its share of controversies4.

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Of all the breast cancers diagnosed irrespective of mode of detection, 70-80% were of the invasive ductal type5. These invasive cancers when detected at screening are however at an earlier developmental stage and more likely to be smaller and of lower grade6,7, correlating with better prognosis compared to symptomatic or interval cancers8. Screen-detected cancers are also more likely to be treated with breast conserving surgery and sentinel node biopsy instead of total mastectomy and axillary node clearance9.
Case Report on screen-detected invasive ductal carcinoma
A 66 year old female patient underwent routine breast screening carried out in her local community. Her mammograms revealed a new 9mm spiculate mass (Figure 1) in the right upper outer quadrant of the breast, not present in her last set of screening films from 2007 (Figure 2). It looked highly suspicious of a carcinoma and was graded as R5 (malignant).
Figure 1. Invasive ductal carcinoma presented as 0.7mm spiculate mass on film mammograms. Taken from [21]
Magnified craniocaudal (CC) view of the mass.
Magnified mediolateral oblique (MLO) view of the mass. There are several long but fine spicules radiating from a central mass.
A
B
Figure 2. Normal screening film mammogram of the right breast taken in 2007.
A. CC view
B. MLO view
She was subsequently recalled to the hospital for further assessment, which consists of further imaging and needle biopsy. Clinical examination was insignificant, while a coned compression mammogram further confirmed the presence of the mass (Fig). Ultrasound scan showed a 9mm irregular hypoechoic area with posterior acoustic shadowing (Fig), giving a grade of U5 (malignant) and a core biopsy was obtained using ultrasound guidance.
The histopathology report of the core biopsy confirmed a finding of invasive ductal carcinoma (IDC), provisional grade 2 on microscopic examination. A supplementary report showed it to be oestrogen-receptor (ER) and progesterone-receptor (PR) positive, and HER-2 negative.
Later during the week, patient was given the diagnosis of IDC and agreed to breast conserving surgery that will be done with the help of ultrasound localisation. A sentinel node biopsy will also be carried out. After the surgery, the excised tissues and sentinel lymph node will be analysed in the laboratory, and the histopathology results will indicate the prognosis and course of future treatments for the patient.
This plan of action was agreed upon during a multidisciplinary team meeting and the patient will be reviewed again in the meeting after the surgery.
Discussion
Epidemiology of breast cancer
Breast cancer is an important public health issue in the UK to date. In 2006, the incidence of breast cancer in the UK was approximately 46,000, representing a two-fold increase over a 30 year period1. In this similar time period, a fall in breast cancer mortality rates was seen10 (Figure 1). This can be attributed to advancements in the management and treatment of breast cancers and early detection of cancers from screening. The opposing trend in incidence on the other hand, can be accounted by a change in environment and lifestyle as well as an increase in cancer detection after the introduction of the breast screening10.
Figure 1. Age standardised (European) incidence and mortality rates of female breast cancers in UK from 1975 to 2005. Taken from [10]
Breast screening programme in the UK
The National Health Service Breast Screening Programme (NHSBSP) was introduced in the UK in 1988 in response to ‘The Forrest report’ which concluded that women aged 50 and over can lead a longer life as a result of mammographic screening11. The NHSBSP initially screened women between the age of 50 and 64 once every 3 years using single view mammography but has made changes with new evidence from randomised controlled studies12,13.
Currently, the NHSBSP screens women from 47 to 73 years of age using double view mammography and this has improved the detection rates of small cancers12,14. It has been estimated that since the programme began, over 100,000 breast cancers have been detected15.
Mortality from breast cancer has been shown to decrease by 25% in the UK13 and it has been reported that NHSBSP saves approximately 1400 lives annually2. These figures demonstrate an apparent benefit of a breast screening programme which is vital as screening essentially diagnose otherwise healthy women with cancer. Without a clear benefit, in light of evidence that screening can do harm, it would be difficult to justify its use on such a large scale.
Overview of the breast screening process
Figure 2. The breast screening process in the UK. Taken from [10].
All women between the age of 47 and 73 in the UK who are registered with a general practitioner (GP) are eligible for breast screening under the NHSBSP. The process of screening is summarised in Figure 2. There has been further expansion of the screening age group after year 2008 from women aged 50 to 70 years to include women aged 47 years and over up until 73 years of age22. Women over 73 years of age can continue to be screened provided they request it from their GPs.
The GP is responsible for identifying and inviting those who are eligible for screening. The basic screen normally takes place in the community, for example on a mobile screening van, in order to improve the uptake of screening by the population. A minimum target of 70% uptake from those invited is necessary in order for NHSBSP to be cost-effective14. In the UK about 75% of those invited attended for screening2.
The basic screen involves x-ray mammography taken in two views which are the mediolateral oblique and craniocaudal view. Each set of mammogram is then interpreted by two trained readers, independant of each other, a process supported after results of double reading in screening17. When there are any discrepancies with the readings, they are further reviewed during the process of consensus and arbitration. A large majority of women screened will have normal mammograms and will be sent a letter within 2 weeks regarding their results. They will then continue to remain in the normal screening programme.
Around 3 to 10% of women will be recalled for assessment either due to findings on mammograms or technical recall10. Findings on mammograms which warrant further assessment include appearance of masses, microcalcifications, architectural distortion and asymmetric densities2. It is estimated that around 1 in 10 women recalled will have the diagnosis of breast cancer14. Recall rates for ‘prevalent round’ screens are higher compared to ‘incident round’ screens while digital mammography have reduced the number of technical recalls compared to film mammography.
Women who have then been recalled for further assessment will undergo additional imaging using an ultrasound scan. Further mammographic imaging, clinical examination and needle biopsy may be carried out as well. This stage in assessment may incorporate a multidisciplinary approach, involving radiologist, radiographers, pathologists, as well as breast surgeons. Such a structure can ensure that women are thoroughly assessed, and those with normal findings can be reassured immediately. Patients who have undergone needle biopsy however, will have to be brought back to the clinic in about a week’s time for their results. Less than 1% of these women will require surgical referral and the rest will return to the normal screening programme10.
Advantages and disadvantages of mammography
Mammography has undergone many randomised trials for its use in breast screening and is still currently the gold standard method for screening. It has been shown that breast cancers detected from mammography screening are more likely to be smaller, and of lower grade which have yet to infiltrate into the surrounding lymph nodes16. This stage shift of screen-detected cancer is largely responsible for the improved survival, as survival is dependant on size, grade and lymph node status of the cancer according to the Nottingham Prognosis Index (NPI).
Mammography as a screening modality is not perfect as it has its disadvantages. The recall of women following breast screening is associated with a higher degree of anxiety and emotional distress20. Even though women who are diagnosed with breast cancer through screening or symptomatically experience similar levels of anxiety, women who experience false positive recalls (1 in 8 regularly screened over a period of 10 years) 2 may suffer from anxiety that may persist for some months. After 3 months however, their levels of anxiety are no different from control groups2.
Another issue for concern is the radiation risk of mammography. X-rays from mammography will cause one breast cancer death for every 14000 women screened over a period of 10 years2. The risks posed to the 50 to 70 age group however, is small when taken into account the benefit of reduced mortality. It is estimated that 40 breast cancer deaths is prevented at the expense of 1 breast cancer death from radiation exposure18.
There are also more cases of breast cancer diagnosed in women who attend regular mammographic screening. These cancers tend to be small or are pre-invasive in nature – ductal carcinoma in situ (DCIS). The detection of DCIS has increased from 3% to 25% after the start of the screening programme14, and has contributed to a decrease in mastectomies2. Evidence have shown that DCIS may be a precursor for invasive cancer and before the launching of the programme, 1 in 3 women with untreated DCIS, developed invasive cancer 10-20 years later2.
With the rise in cases of breast cancer due to screening there is an issue of overdiagnosing and subsequently overtreating for breast cancer, as 1 in 8 women with screen-detected breast cancer would have succumbed to another illness before their breast cancer have any clinical impact2. These breast cancers whose diagnosis has no impact on overall survival are said to have lead time bias14, with them ending up living with the disease for a longer period of time. Another issue is with length-time bias, whereby cancers that would have otherwise been clinically silent in the woman’s life time due to the low grade nature of the cancer is detected, leading to unnecessary treatment14.
There is currently no way of differentiating between cancers that will prove fatal if left untreated from those that have no clinical consequences. Therefore all cancers diagnosed will be managed with surgical interventions, systemic treatments or both.
Other screening methods
Mammography is not the imaging of choice in women under the age of 40. Young women tend to have more glandular breast tissues which produce mammograms that are more difficult to interpret. There is also the more concerning issue that radiation from annual mammography in women under 40 years may do more harm than good18. As a result, there is an increasing favour towards the use of magnetic resonance imaging (MRI).
Presently, contrast enhanced MRI is sometimes used alongside mammography in diagnosing the extent of disease. MRI is also currently used to monitor patient’s response to systemic treatments such as chemotherapy and is of some value in the screening of high risk patients. Studies have also shown that MRI has greater sensitivity in detecting both invasive and in situ carcinoma compared to mammography. However these are small studies and MRI has its fallbacks in terms of costs and high false-positive rates19.
NHSBSP screen patients with low risk of breast cancer, and any patients with increased risk are offered screening outside of the programme. These women are offered yearly screening as opposed to the triennial screening offered by the NHSBSP. The starting age of screening will largely depend on the calculated risk for each individual woman. High risk women are offered screening at around the age of 30 to 35, while women with moderate risk begin screening at 40 years of age20. There are risks involved in screening of younger patients and they must be well informed of the potential harms they may incur as a consequence.
Screen-detected cancers
Overview
Recent controversies
A narrative review4 was recently published in the Journal of the Royal Society of Medicine which critiques the NHSBSP 2008 annual review15. The review challenged the conclusion of the NHSBSP annual review and criticised it for emphasizing too much on the benefits of breast screening and overlooking its harms.
This narrative raised controversial issues regarding the benefits and harms of the screening programme despite convincing evidence of a reduction in mortality with breast screening3. Nevertheless, with favourable support for the latter2,3, it is difficult to ascertain whether there is more harm than good for breast screening, as speculated by the review.
One of the authors of this review also published a Cochrane review10 with a conclusion that breast screening is likely to reduce mortality but whether the benefits outweighed the potential harms of screening is still questionable.
Challenges and controversies raised in such publications is a crucial process as it is through debate and discussions that ways of improving and developing the breast screening programme will be proposed by experts in order to resolve the conflicts.  
Conclusion
With the benefits of early detection of potentially fatal disease, the NHSBSP will inevitably result in the overdiagnosis and overtreatment for breast cancer in some women. As it is not yet possible to determine whether cancer detected through screening will be fatal or not, it seems unethical to leave cancers untreated due to potential for harm. This issue will remain controversial until new evidence and research arise, but until then, it is important to keep women well informed, so they can make the choice that is right for them.