Monday, October 14, 2013 C7
HEALTH 3-D mammography may improve breast cancer detection, but its effectiveness is unproven, writes Jeanette Wang
LAB REPORT .............................................. Jeanette Wang jeanette.wang@scmp.com
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hree-dimensional technology has reproduced a relatively faithful representation of physical reality in film and on television, and now it has the potential to do the same with breast cancer imaging. Breast tomosynthesis – or 3-D mammography, in layman’s terms – significantly improves breast cancer detection while simultaneously reducing recall rates over conventional 2-D mammography, according to supporters of the new technology. But some experts warn that the benefits are not yet proven. Moreover, they say that tomosynthesis also exposes women to even more unnecessary radiation, since it’s carried out on top of conventional mammography. “Tomosynthesis hasn’t yet replaced 2-D mammography, but it’s very promising,” says Dr Hung Wai-ka, honorary medical adviser to the Hong Kong Breast Cancer Foundation’s Breast Health Centre. Breast tomosynthesis was approved by the United States Food and Drug Administration in February 2011. It first appeared in Hong Kong later that year, at Tung Wah Group of Hospital’s Well Women Clinics, according to the clinics’ honorary consultant, Dr Lui Chun-ying. Lui explains the technology behind 3-D mammography: an X-ray arm sweeps in a slight arc over the breast, taking multiple images in a matter of seconds. A computer then produces a 3-D image of the breasts in 1mm slices, providing greater visibility for radiologists to see tissue details. An exam using tomosynthesis takes about four seconds – similar to a conventional mammogram. It was at the Well Woman Clinic, in Kowloon, that Hung, a specialist in general surgery, first used 3-D mammography. “Research data is still limited, but it’s being used all over the world and experience will eventually accumulate,” he says. “In my opinion, it definitely helps improve cancer detection because it gives a clearer picture with a single mammogram. It has definitely boosted my
Vitamin D supplements not needed by healthy adults You may be loading up on vitamin D supplements to maintain bone density and strength and prevent osteoporosis, but a new report published in The Lancet suggests that most healthy adults do not need these pills. Researchers from the University of Auckland in New Zealand conducted a systematic review and metaanalysis of all randomised trials examining the effects of vitamin D supplementation on bone mineral density in healthy adults up to July 2012. From 23 studies involving more than 4,000 healthy adults (average age 59 years), no significant effects were found in people who took vitamin D for an average of two years. Dr Hung Wai-ka, honorary adviser to the Hong Kong Breast Cancer Foundation, shows what a 3-D image of the breast looks like. Photo: Jeanette Wang
Nowhere to hide confidence in screening and diagnosis.” Though tomosynthesis is being used as a screening tool in the US, in Hong Kong it is primarily used during patient recall for further evaluation of suspicious lesions that show up on 2-D mammograms. At Hong Kong Sanatorium & Hospital, 3-D mammography has been used since February 2012, says Dr Gladys Lo, radiologist-in-charge at the hospital’s Department of Diagnostic & Interventional Radiology. “[Tomosynthesis] is more beneficial for clarifying suspicious mass than a 2-D mammogram,” she says. Tomosynthesis could be used for a first screening – although it costs about double the price of a conventional mammogram – but Lui says the service is not being actively promoted. Tomosynthesis may be better for certain women. “Young women with dense breasts or Asian women with smaller breasts may benefit from this new technique,” says Dr Alex Ching, a radiologist at Matilda International Hospital, which only offers conventional mammography.
Breast tomosynthesis (3-D mammography) involves having an X-ray source move around the breast. Photo: Courtesy of Hologic
“There is some ongoing research on the potential benefits for those women with implants, different races, highrisk groups and patients with lumpectomy (partial removal of breast tissue).” Ching adds that the 3-D machine is more comfortable for women because it requires less compression of the breast during the procedure. Conventional mammography has played a significant role in women’s health, reducing the mortality rate from breast cancer by as much as 50 per cent. But it has its limitations. The fundamental flaw is that when the breast structure is compressed into a standard 2-D mammogram, overlapping tissue may hide lesions or cause benign areas to appear suspicious. This leads to callbacks of healthy patients, causing unnecessary anxiety and sometimes additional examinations such as ultrasounds. According to the US National Cancer Institute, as many as 30 per cent of breast cancers are not detected by mammography and 8 per cent to 10 per cent of women who undergo mammogram screening are recalled for an additional check. The overall recall rate of Tung Wah’s screening programme is 8.8 per cent. “Because of these limitations, 3-D mammography has the advantage of removing overlapping breast tissue so that we can see clearly where the lesion is,” says Lui. “It also defines the lesion more accurately: whether it’s a regular or irregular mass, smooth mass, or if there’s radiating lines or distortion of the lesion.”
The downside: the radiation dose from a 3-D mammogram is about 0.5 to 1.0 millisieverts – about 20 per cent more than a conventional mammogram. But it is still within the FDA’s safe limits and relatively low in comparison to a CT scan of the head (about 2.0 millisieverts). “[Tomosynthesis] is the first major advance in breast imaging and breast cancer screening since the development of breast MRI,” says Dr Elizabeth Rafferty, director of breast imaging at Massachusetts General Hospital in Boston, the first to perform a clinical 3-D breast tomosynthesis exam in the US, in March 2011. Rafferty has spent more than 10 years researching tomosynthesis. In one of her studies, published in the journal Radiology in November 2012, some 1,200 women underwent a standard digital mammogram followed by tomosynthesis, and the results were read by 27 radiologists. Compared to digital mammography alone, the use of both standard mammogram and tomosynthesis resulted in increased diagnostic accuracy, and significantly decreased recall rates for further testing when no cancer was present (called a false positive result), for
There is no solid data to prove that the 3-D technique finds more cancers DR ALEX CHING, RADIOLOGIST
calcifications. all the radiologists. In a similar study, In the Italian breast Taiwanese tomosynthesis researchers screening trial, from 7,300 women Kaohsiung aged 48 years and Veterans older had both of breast cancers General 2-D and 3-D go undetected by Hospital, mammograms. mammography studying about Radiologists then 60 Taiwanese read the screens patients, had similar in two phases – results – so, too, did 2-D only, then radiologists at Tianjin Medical integrated with 3-D. University Cancer Institute and The combination of tomosynthesis and conventional Hospital, who assessed about 130 Chinese women. mammography identified 8.1 At Singapore’s Khoo Teck cancers per 1,000 screens, Puat Hospital, 50 women were compared with conventional screened using both 2-D and mammography’s 5.3 per 1,000 3-D mammography. screens, an increase in the The researchers concluded cancer detection rate of 53 per that tomosynthesis is “an cent. The results were published important tool to reduce recall in April this year in The Lancet rates and to improve breast Oncology. cancer detection, keeping Researchers at Yale Cancer patient [radiation] dose within Centre reported a 30 percentage safe limits” and that the findings point drop in recall rates – from support that the technology 12 per cent to 8.4 per cent – “can be used as [a] robust among their patients using screening method in future”. tomosynthesis versus Lui says Tung Wah is doing conventional mammography. an observational study on its The study, published in the July 2013 issue of Radiology, involved clinics’ initial experience of using tomosynthesis. The goal is more than 13,000 women, of to confirm whether there are whom 6,100 had tomosynthesis. advantages for the Hong Kong Most studies, however, have population, its safety, and the involved Western women. Asian response of the radiologists, women, in general, have surgeons and patients to the relatively smaller and denser new technology. breasts, which may be an For now, the technique obstacle to detecting abnormal should not be used outside of a lesions. Studies done in Asia, clinical trial as it is not a “standhowever, have been small scale. alone” test yet and does not A study in this year’s annual replace a regular mammogram, Asia Pacific Journal of Cancer says Matilda’s Ching. Prevention by Japanese “There is as yet no solid data researchers found that among to prove the 3-D technique about 100 Japanese breast finds more cancers or save cancer patients, tomosynthesis more lives than traditional 2-D was superior in diagnosing lesions in the form of mass, focal mammogram,” Ching says. asymmetry or distortion, but not jeanette.wang@scmp.com
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Overweight and obese children face high risk of hypertension Extremely obese children and adolescents are 10 times more likely to have hypertension than their normal-weight peers. In fact, according to a Kaiser Permanente Southern California study, any excess weight in youth is linked with
the likelihood of hypertension: twice as likely for the overweight and four times for the moderately obese. The study included nearly 250,000 children aged six to 17, tracked over three years. High blood pressure can lead to heart and kidney disease. Because it may show no symptoms for years, the researchers advise paediatricians to be vigilant about screening overweight children for hypertension. The study appears in The Journal of Clinical Hypertension. Beneficial gene variation proves to be a double-edged sword A genetic variation commonly present in light-skinned people that could protect skin from sun damage has been found to fuel testicular cancer. In a study in the journal Cell, scientists from Ludwig Cancer Research at Oxford University discovered a gene mutation that affects the activity of a protein named p53, which is best known as the cell’s most important defence mechanism against cancer. The mutation was found to be tightly linked to the risk of developing testicular cancer. At the same time, the detection of ultraviolet light damage from the sun activates p53 in certain skin cells to ramp up melanin production and produce a protective tan.
Women urged to increase screening schedule ................................................ Jeanette Wang jeanette.wang@scmp.com With breast cancer being the most common cancer among Hong Kong women, you’d think people would be vigilant about examining themselves regularly for the disease. Unfortunately, the opposite is true – one in two women do not check their breasts regularly, according to a new survey, commissioned by the Hong Kong Cancer Fund, of more than 500 local women aged over 18. What’s more startling is that among those who do not do examine themselves, the most common reason – 36 per cent gave – is that they “do not see the need for doing it” or “breast cancer will never happen to me”. Well, it can. According to the Hong Kong Cancer Registry, there were 3,014 new cases of breast cancer in 2010, compared to 1,918 in 2000. Early detection and treatment greatly increases the chances of being cured, yet
only a third of breast cancer cases in the city are found at stage one. “The incidence of breast cancer in Hong Kong has doubled in the past 20 years, with one in every 19 women suffering from some form of breast cancer,” says Dr Raymond Liang Hin-suen, assistant medical superintendent and director of the Comprehensive Oncology Centre at the Hong Kong Sanatorium & Hospital. “All women should be vigilant and know breast cancer symptoms, as well as check their breasts regularly.” A change in the skin texture of the breasts or rashes found on or near the nipple are warning signs, says Liang. Other symptoms include: change of shape or location of breasts; persistent pain on or near the breast or underarm; abnormal nipple discharge; and lumpiness or dimpling found in breasts. Dr Hung Wai-ka, honorary medical adviser at the Hong
Kong Breast Cancer Foundation’s Breast Health Centre, recommends women 40 and older get a mammogram every two years, a doctor’s examination every two years, and do breast self-examination once a month. For women under 40 with normal risk, a doctor’s examination every three years and monthly breast selfexamination is sufficient. Liang
says women at high risk should discuss the best screening schedule with their doctor. Age (above 50 years) and a family history of the disease are risk factors, as well as not having children, having the first child at an older age, no breastfeeding experience, drinking large amounts of alcohol, excess body weight and genetic factors. According to the Cancer Fund survey, a majority of
Women under 40 should be checked every three years. Photo: Corbis
respondents also demonstrated a poor understanding of the symptoms. Only one in 10 of women polled knew that breast self-examinations should start at age 20, and less than a fifth knew that mammograms should start at age 40. Guidelines for the starting age for mammography screening to prevent breast cancer deaths can be conflicting. In 2009, the US Preventive Services Task Force proposed screening for women aged 50 to 74 years once every two years. This is because some studies show that routine screening leads to overdiagnosis and unnecessary treatment, including biopsies, lumpectomies and mastectomies, and weeks of radiation and potentially toxic drugs. False positives result in avoidable procedures and psychological trauma. Some other researchers have produced a contrary view. A study published last month in the American Cancer Society
The incidence of breast cancer in Hong Kong has doubled in the past 20 years DR RAYMOND LIANG
journal Cancer found that most deaths from breast cancer occur in younger women who do not have regular mammograms. The research team, led by Dr Blake Cady of Harvard Medical School, looked backwards from more than 600 confirmed breast cancer deaths to discover correlations at diagnosis. Nearly 30 per cent occurred among those who had been screened and about 70 per cent were among unscreened women. Only 13 per cent of deaths occurred in women aged 70 or older, but half occurred in women under 50.
Dr Lui Chun-ying, honorary consultant at Tung Wah Group of Hospital’s Well Women Clinics, says the pattern of breast cancer in Asia is different from that in the West. “In the West, there’s a higher incidence of breast cancer in women of increasing age, but in Asian countries, such as Hong Kong, Taiwan and Singapore, the age of the cancer is more in the range of 45 to 50. We recommend screening at the age of 40,” Lui says. The Cancer Fund, in collaboration with the Hong Kong Sanatorium, is offering 500 Hong Kong residents aged 40 or above a discounted mammogram screening for HK$600. The normal price is HK$1,600. Women who have not received any clinical breast cancer screening in the past two years can apply for the discount through the Cancer Fund, tel: 3656 0800. The offer runs until October 31 and is on a firstcome, first-served basis.