Since the late 1980s, mammography has become a standard
medical process to screen women for breast cancer and detect the disease early. A study published last year in the New
England Journal of Medicine found that 1.5 million additional women have been
diagnosed with early stage breast cancer as a result of widespread
screenings. Most would think that early
identification of breast cancer is key in preventing progression to later
stages, however, the study found that the number of women diagnosed with
late-stage breast cancer had only been reduced by 0.1 million. What does this startling trend mean? Overdiagnosis.
In a New
York Times article, “Cancer Survivor or Victim of Overdiagnosis?,” H. Gilbert
Welch, a professor at the Dartmouth Institute for Health Policy and Clinical
Practice, explains the implications of this research: “more than a million
women who were told they had early stage cancer
— most of whom underwent surgery, chemotherapy
or radiation — for a ‘cancer’ that was never going to make them sick.” As mammogram technology continues to advance,
more and more breast abnormalities are being detected, which has caused
overdiagnosis to increase. While in the
1980s approximately a quarter of screenings were overdiagnosed, this statistic
has increased to between a third and a half.
In addition to prompting onerous
treatments, mammograms may also not affect breast cancer mortality rates. Three recent studies in Europe have found
that mammograms reduce mortality by no more than 10% and perhaps not at all. This is not to say that breast cancer
mortality is rising. On the contrary, in
both Europe and the United States, morality rates have dropped considerably
since the 1980s. But this good news is not
the result of early diagnosis but rather superior methods of treatment. As therapy for breast cancer improves,
mammography becomes less crucial in combatting the disease.
However, because women are
aggressively encouraged to get mammograms, this method of screening remains
prevalent. Those who promote mammography
believe that detecting breast cancer early is key to stopping the disease from
progressing to later stages. In reality,
survival rates increase with early diagnosis because people are living longer
with their diagnosis, even though they are not actually living longer than they
would if they had not been screened.
Thus Welch believes that those who survive breast cancer do not survive
because the disease was detected early, but rather because their cancer was
overdiagnosed, and they would not have died anyway. Similarly, those who die from breast cancer
are destined to die whether the disease is detected early or not.
While this research should
certainly be verified, if it does prove to be accurate, women need to become
better informed about the risks and benefits of mammography. If a woman has a very small chance of
developing life-threatening breast cancer, the risks of a mammogram may
outweigh the benefits. Welch suggests
that physicians “[. . .] can look less hard for tiny cancers and precancers and
put more effort into differentiating between consequential and inconsequential
cancers.” While Welch affirms that
diagnostic mammography (when a woman already has a breast lump) is important, he
strongly opposes the provision of anticipatory mammograms to all women.
Though mammography may not need to
be ubiquitous, breast cancer cannot be treated if it is not detected. Thus mammography remains an undeniably useful
tool. It is likely that follow-up
research will be conducted to further explore the effectiveness of
mammography. In any case, as breast
cancer treatment improves, women will hopefully not have to be concerned about
developing breast cancer and overdiagnosis will become less apparent.
2 comments:
This article raises some interesting questions about the importance of mammography and its actual impact on the breast cancer survival rate. Although it suggests regular screening might not be an efficient means of increasing this rate, early detection is a key element in the fight against cancer. H. Gilbert Welch argues in favour of only “diagnostic mammography”, which he uses to mean a mammography when a woman already has a lump, but if this were the only type of detection, it would be too late in most cases. A tumor that is large enough to be felt through the skin has already grown to a considerable size, which indicates that the risk of the cancer spreading has increased. Mammography is still considered one of the tools that save the most lives, according to the leading Susan G. Komen breast cancer foundation. Detecting a tumor in its initial stages prevents invasive treatments and increases the likelihood of survival. Time is the most important factor in most types of breast cancer (detecting a stage 1 tumor is significantly better than detecting a stage 4 one). In most countries, women of average risk over the age of 40 are encouraged to pursue some form of screening (either a standard mammography, an MRI or a clinical breast exam) yearly or every two years. Although the concerns of over-diagnosis are relevant and have caused a worldwide debate about the best forms of treatment for women, the risk that a ductal carcinoma in situ (DCIS) (a lump that can be misread as breast cancer) will turn into cancerous cells if left untreated is high enough that every case should be addressed (20-30% of DCIS develop into cancerous cells).
Breast cancer is a delicate subject, precisely because there is no known cure or definitive detection method. Currently, mammography is still considered the most effective tool for early detection and it should not be set aside for fears of over-diagnosis.
Sources:
Susan G. Komen
http://ww5.komen.org/BreastCancer/TheMammographyDebate.ht
Concerns about over-diagnosis of breast cancer through mammography seem valid in context. Perhaps through government funding and advocacy through organizations such as Susan G. Komen, public awareness about breast cancer has reached incredible heights. There are clearly advantages to this. Treatment for breast cancer has progressed substantially. Women know the signs for breast cancer and early detection leads to more positive outcomes. But excessive anxiety in women about developing breast cancer is a downside. Since the discovery of a mutation in the BRCA gene as a risk factor for breast cancer, women are increasing getting tested and undergoing preventive mastectomies. While preventative surgery will definitely reduce incidence of breast cancer, it is doubtful that this is the right direction for women in society. Since the genetic mutation in no way guarantees development of breast cancer, clearly many women have undergone invasive surgery for no reason.
Also, the same phenomenon of over-diagnosis is also occurring through screening of other cancers, such as lung cancer. This is partly due to the advancement of screening technology. Currently, high definition imaging technologies with the ability to detect the smallest abnormalities are frequently used in cancer diagnosis. Some experts have noted that the use of high-definition imaging has caused doctors to look harder for cancers, and they are finding them. Another possibility is that physicians are eager to detect cancer early out of fear of being sued for malpractice. Breast cancer patients with adverse outcomes could cast blame on doctors for not finding the tumor early enough. Evidently, medical practice concerning breast cancer is strongly influenced by perceptions in society.
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