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'There Is a Reason for Optimism': Breast Cancer Interview with Public Health Researcher

Hans-Olov Adami is a Swedish physician, academic and public health researcher. He established the largest epidemiologic and biostatistics research unit in Sweden and has served on the Governing Board of the European Academy of Cancer Sciences since it was established in 2009. Moreover, Hans-Olov Adami has been a member of the Nobel Assembly that awards the Nobel Prize in Medicine.

In 2019, he joined the Medical Board at Flo and today answers the most topical questions on breast cancer. 

How common is breast cancer?

Worldwide, breast cancer is the most commonly occurring cancer in women with an estimated 2 million newly diagnosed cases worldwide in 2017 and over 600 000 deaths with breast cancer as an underlying cause. 

Overall, breast cancer accounts for 25% of all cancer diagnoses in women. Because cancer registration covers only a small proportion of the global population and only a minimal fraction of for example countries in sub-Saharan Africa, detailed data on breast cancer incidence are somewhat uncertain. 

Worldwide, breast cancer is the most commonly occurring cancer in women with an estimated 2 million newly diagnosed cases worldwide in 2017 and over 600 000 deaths with breast cancer as an underlying cause.

Existing estimates indicate, however, that breast cancer even in sub-Saharan Africa is the most common or the second most common (preceded by cervical cancer) malignancy among women. It is also well established that incidence rates vary more than 5-fold internationally. 

What are the survival rates for breast cancer?

Survival rates vary widely between geographic regions with generally a gloomy outcome for example in sub-Saharan Africa and other areas in the world with less developed health care systems and lower awareness of breast cancer symptoms – often with a component of denial and reliance on traditional healers. 

There is a great opportunity to use modern communication technologies, particularly smartphones, in order to enlighten women about early symptoms of breast cancer and increase their awareness.

In western countries with optimized treatment, prognosis has successively improved over the last decades, particularly after the introduction of systemic adjuvant treatment with chemotherapy or hormones. Hence, overall long-term survival rates in the order of 70-80% are now commonly seen in western countries. 

Why is early diagnosis so important?

The impact of early diagnosis is not as straightforward as one might believe. 

On one hand, women diagnosed in early stages – with small binary tumors, no axillary metastases nor any distant spread – undoubtedly have much more favorable outcome than women diagnosed in more advanced stages. 

It is much more controversial, however, whether breast cancer mortality can be further reduced if women who now have a high level of awareness and see a doctor early would have a better outcome if diagnosed through mammography screening already when they are asymptomatic. This is indeed a highly controversial area. 

It is highly likely that many healthy habits that reduce the risk of other chronic diseases and numerous cancers, also reduce the risk of breast cancer. These include maintaining a healthy weight, consuming alcohol moderately, being physically active and refraining from smoking.

Recent evaluations of mammography programs in Norway, Denmark and the Netherlands have indeed failed to document any meaningful reduction in breast cancer mortality attributable to screening. Hence, a minimal, if any, mortality reduction from screening has to be weighed against the harms that include false positive alarms and much more substantial overdiagnosis of non-lethal cancers and lesions that are presumed precursors (carcinoma in situ) of invasive cancer. 

Can blood tests help to detect breast cancer earlier?

There is no established test that is able to detect breast cancer earlier.

What key things about breast cancer would you like every woman to know?

Like all human malignancies, breast cancer develops through a combination of genetic factors, bad luck and lifestyle.

Although many lifestyle factors are known, the causes of breast cancer are extraordinary complex and only partially understood. Many of these factors are unrealistic or impossible to modify.

It is highly likely that many healthy habits that reduce the risk of other chronic diseases and numerous cancers, also reduce the risk of breast cancer. These include maintaining a healthy weight, consuming alcohol moderately, being physically active and refraining from smoking. 

Is breast cancer more prevalent in certain areas of the world? If so, why?

Prevalence is an informative measure because it is the net result of incidence and prognosis following treatment (which is much poorer in many developing countries and areas such as sub-Saharan Africa). Although the 5-fold international disparity in incidence may not be fully explainable some of the factors have been outlined above. In addition, completeness of cancer registration probably plays a role. 

Many women with metastatic and incurable disease can expect a disease remission and indeed live many years.

Even in developed countries – chiefly the US and Europe – we often observe a slowly increasing trend in incidence which is complex to explain. There was, however, a transient increase in the early 2000s which has been generally attributed to the documentation that hormonal treatment for menopausal symptoms increases breast cancer risk which entailed a dramatic drop in the prescription of such drugs. 

Factors that likely contribute to a continuing increase in incidence include continued changes in reproductive factors as well as the constantly growing obesity epidemic. A somewhat neglected by probably important factor is also the overdiagnosis of cancers detected by mammography screening, lesions that would never have surfaced clinically in the absence of such screening. 

Breast cancer recurrence. What are the chances of breast cancer coming back?

We need to distinguish local recurrences from distant metastases. Although local recurrence is an unfavorable prognostic sign, the are often curable, at least locally, through various combination of surgical removal, radiotherapy and perhaps a combination with systemic treatment. 

If, on the other hand, breast cancer is diagnosed with metastases, a permanent cure is usually beyond reach. However, increasingly efficient palliative treatments have become available. 

A first-degree family history increases breast cancer risk by about 50-100%.

Hence, many women with metastatic and incurable disease can expect a disease remission and indeed live many years. The risk of encountering a systemic disease is essentially the reversal of long-term cure rates. Hence, if 70% of women with breast cancer experience a 70% long-term survival, we would expect that about 30%.

What do you suggest is the best plan of action for women who have a family history of the disease?  

A minority of these women have inherited highly penetrant genetic determinants of disease and should ideally undergo genetic testing. 

There are few rare genetic syndromes that entail such a high risk that prophylactic mastectomy should be discussed with the women. For the majority, however, a first-degree family history increases breast cancer risk by about 50-100% (relative risk 1,5-2,0). 

It would be tempting to recommend more frequent mammography screening. 

But, unfortunately, there is accumulating evidence that mammography has minimal if any effect on breast cancer mortality in the current era of effective systemic adjuvant treatment. Hence, women with a family history should in general take no special action but rather be assured that awareness might be beneficial and that treatment is often curative. 

What are the most important prognostic factors in breast cancer? 

Since about half a century, a myriad of factors has been identified that predict the prognosis in breast cancer – and new markers of prognosis are constantly discovered.  

The big divide is, however, whether a woman has distant metastases already at the time of primary diagnosis which in virtually all instances makes the disease incurable although palliative treatment is still possible.  

Fortunately, in western countries only a minority of women are diagnosed in such a late stage. And among them, the most important prognostic factor is whether or not the primary tumor has spread to the axillary nodes.  

Until a few decades ago, removal of lymph nodes in the axilla was usually part of primary treatment. And the prognostic outlook could be graded depending on the number of nodes affected and also on information whether tumor growth in the lymph node had extended through its capsule. But because axillary dissection also causes substantial side-effects such as arm edema, stiffness and consequences of nerve damage, the standard procedure now is to examine the sentinel node which is the first lymph node that trains the mammary gland tissue.  

In general, documentation of hormone receptors for estrogen and progesterone is also a considered favorable prognostic factor although it might vanish over follow-up time. 

Modern research. What are the current and future directions in breast cancer research?

Research on breast cancer biology (basic research), causes (epidemiologic research) and treatment (surgery, medical oncology, and radiotherapy) is, - and has for decades – been ongoing on a myriad of fronts that cannot be easily summarized. Furthermore, discoveries are by definition unpredictable.

Hence, I believe the most reasonable answer to your question is that there is a reason for optimism. Enormous efforts are ongoing and we have seen substantial progress over the last several decades. 

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