DOI: 10.12809/hkmj164916
© Hong Kong Academy of Medicine. CC BY-NC-ND 4.0
EDITORIAL
Mammography for breast cancer detection in Hong Kong
Kathy CK Wong, FHKCR, FHKAM (Radiology)1; CY Lui, FHKCR, FHKAM (Radiology)2
1 Department of Diagnostic and Interventional Radiology, Kwong Wah Hospital, Yaumatei, Hong Kong
2 Hong Kong Women’s Imaging
Limited, Suite 319, 3/F, Central Building, 1-3 Pedder Street, Central, Hong Kong
Corresponding author: Dr Kathy CK Wong (kathyckwong@gmail.com)
Breast cancer poses a significant health burden
worldwide. It is the most common cancer in women
with nearly 1.7 million new cases diagnosed globally
in 2012.1 Early detection reduces mortality and
mammogram screening has been shown to achieve a
mortality reduction of 25% to 28%.2 3 Many countries
have a breast screening programme, including the
UK, Australia, Norway, Sweden, the US, Singapore,
Japan, and Korea. Population screening for breast
cancer remains controversial, however, especially
the decision on whom, when, and how to screen
due to different epidemiological characteristics
of breast cancer in different populations. In Hong
Kong, the incidence and mortality of Asian female
breast cancer is lower compared with the Caucasian
population. In the Surveillance and Health Services
Research in 2013, the American Cancer Society
published a lifetime risk of 1 in 8 for developing
invasive female breast cancer,4 similar to the findings
of Cancer Research UK in 2010.5 The median age
at diagnosis of cancer was 61 years in 2006 to 2010
in these studies. In Hong Kong, breast cancer is
the number-one female cancer with 3524 cases of
invasive cancer diagnosed in 2013. The lifetime risk
of female breast cancer before the age of 75 years
was 1 in 17. Breast cancer in Hong Kong occurs at a
younger age compared with the western population.
The median age at diagnosis of breast cancer was 54
years.6 Due to different tumour characteristics and
the overall smaller size and denser fibroglandular
tissue of Asian women’s breasts, local epidemiology
and clinical studies are important to facilitate our
understanding of this common disease in Hong
Kong. In this issue of the Hong Kong Medical
Journal, studies conducted by Lau et al7 and Chan et
al8 in Hong Kong provide valuable local data on this
important topic.
Lau et al7 compared the surgical outcome
and pathology of breast cancer in self-detected
and screen-detected women (physical breast
examination, mammogram, or ultrasound) in their
institute in Hong Kong. Several interesting aspects
are raised. First, the screen-detected group had a
smaller tumour of an earlier stage and lower grade
with less lymph node involvement. This could imply
that early detection may result in better prognosis.
Previous studies have suggested reduced mortality
with early breast cancer detection.9 Less-invasive
surgery is feasible such as breast-conserving
surgery with better cosmetic outcome. Second, there
was a trend towards increased detection of smaller
tumours of <2 cm in the screen-detected group,
likely explained by the advances in radiological
imaging technology in mammogram and ultrasound.
The self-detection trend remained static suggesting
no significant change in skills throughout the
study period. While the difference did not reach
statistical significance, the trend could suggest a
higher sensitivity of radiological imaging to detect
small tumours. Third, the mean age at first diagnosis
of breast cancer was 50 years (range, 24-92 years)
and median age of 40 to 49 years in both the self-detected
and screen-detected groups in this study.
This is substantially lower than the median age of 54
years reported in the Hong Kong Cancer statistics
in 20136 and the age of 61 years reported for the UK
and the US in 2010.4 5 Notably, the highest proportion of
breast cancer was detected in the 40- to 49-year-old
age-group in this study (38.6% and 43.5% of the self-detected
and screen-detected group, respectively).
A striking proportion of breast cancer was also
detected in the 20- to 39-year-old age-group (16.6%
and 7.0% in the self-detected and screen-detected
group, respectively). This finding of breast cancer at
younger age deserves further research and attention.
Chan et al8 explored the impact of a radiolucent
MammoPad (Hologic Inc, Bedford [MA], US) during
mammogram on pain/comfort level, radiation dose,
and image quality. Mammography involves breast
compression in two or more views with radiation
exposure. Discomfort and pain are often encountered
during breast compression and may affect a woman’s
willingness to undergo a mammogram. In their study,
most women (71%) experienced less pain, coldness,
and hardness of the paddle with a better overall
feeling. None of the patients reported additional
discomfort with the pad. Women with less-dense
breasts were more likely to experience more comfort
with the pad. Age and breast size did not relate to
the degree of discomfort during mammogram.
Comparable image quality between the padded
and non-padded side was noted in 92% of women.
While image quality difference was perceived in 4%,
none was considered to have affected the diagnostic
accuracy. Furthermore, glandular dose was 6.5% less
in the mediolateral oblique view and 4.5% less in the
craniocaudal view when a pad was used. Nonetheless,
the role and efficacy of the MammoPad in diagnostic
mammography was not determined in this study due
to the exclusion of women with known carcinoma,
scarring, or pathology detected by clinical breast
examination. Further, the additional time required
and cost of applying a single-use MammoPad may
raise financial concerns in the setting of a publicly
funded large-scale breast screening programme,
unless the cost can be further lowered or pads can
be recycled following effective sterilisation.
Despite agreement on the benefit of early cancer
detection and treatment, debate about population-based
breast cancer screening remains. The younger
age of disease onset identified by Lau et al7 deserves
further attention as high breast density, associated
with younger age and lower body mass index,
reduces mammogram sensitivity. Newer technology
such as digital breast tomosynthesis may provide
higher sensitivity and increase cancer detection rate
compared with digital mammography because of its
ability to remove overlapping glandular tissue, the
main reason for both false-positive and -negative
results with traditional mammography.10 11 12 13 14 Although
tomosynthesis requires breast compression similar
to mammogram, the compression force may be
lower without affecting image quality.14 Further
studies would be helpful to determine whether the
benefits of the MammoPad used by Chan et al8 could
have further benefit in tomosynthesis.
Hong Kong currently has no government-subsidised
programme for breast cancer screening.
Self-financed opportunistic screening is available
mostly in the private sector. The suitability of breast
cancer screening on a population-wide level in Hong
Kong, including cost-effectiveness,15 remains to be
determined. Such a decision should be evidence-based
and tailored to local epidemiology so that the
benefits of screening outweigh the risks. In addition,
the method of screening should be sensitive and
suitable for the woman’s breast density, age, and
personal and family risk of developing breast cancer.
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