Does Early Detection Save Lives?

When we think about screening for breast cancer most will automatically think about mammography as a primary screening test.  The recently published Canadian National Breast Screening Study particularly looked at mammography screening and the results have been very disturbing. This study was conducted from 1980 to 2005, over 25 years and included 90,000 women. This was one of the largest and well-designed studies in the world that looked at the efficacy of mammography screening and the reduction of death from breast cancer.

The results were quite startling that, after 25 years of follow up, breast cancer deaths were almost identical between the mammography group and the control (non-mammography) group. Further, even when looking at deaths that occurred during the screening period in the first five years the numbers between the two groups were identical. Thus there was absolutely no benefit from the mammography screening for women age 40 to 49 as well as for women age 50 to 59.  (see BMJ)

These findings are really important and hopefully will change the way we screen for breast cancer. It is important to note that The Swiss Medical Board recently also recommended that mammography screening should be abolished while presenting the same conclusion. (see Swiss) However, it is not just the ineffectiveness of mammography screening that is problematic but also the potential harm from this way of screening needs to be addressed. 

Using the data from the 25 Year Canadian National Breast Cancer Screening (CNBSS) we can see that many women are told that they don’t have cancer, and therefore getting false reassurance. Further, there are complications from the investigation of false positive tests. The use of mammography increases the false positive rate.  Another useful point to consider is that the mere finding of cancer, as a result of a screening test, does not necessarily imply benefit. Some detected cancers are simply not curable by available treatment. And in other cases, some detected cancer may never have become life-threatening in the patient’s lifetime either because they are cured on their own or they are over diagnosed.

It is important to understand how over diagnosis occurs in mammography screening. In some cases, breast cancer would regress spontaneously if left alone and would not have continued to grow. In other cases, cancer progresses very slow to be threatening even in the longest of lifetimes. The body’s defense mechanism comes into play and arrests the rapid growth of such cancers. Thus the problem of over diagnosis is not something that should be taken lightly as it presents a serious problem. It appears that 22% of screen-detected cases were over diagnosed and 50% of impalpable cases detected by mammography were over diagnosed. In other words, 1 in 424 women who received mammography screening were over diagnosed with invasive breast cancer yet they had no life-threatening disease!

Estimates for non-invasive breast cancers such as Lobular Carcinoma In Situ (LCIS) and Ductal Carcinoma In Situ (DCIS) present us with even more dramatic results. It is assumed that there is a great benefit of surgically removing these lesions because it prevents them from becoming invasive; yet unlike other cancers, it has never been demonstrated that it is true for breast cancer. Based on the CNBSS numbers it has been shown that when it comes to in situ cancers 35% of screen detected cases are over diagnosed and an astounding 72% of impalpable cases detected by mammography are over diagnosed.

The implications for over diagnosis and over treatment are very serious. It shows us that the amount of lead-time gained by mammography has been wrong all along; it is only one year versus previously assumed four years. It is not surprising that all this screening does not impact mortality rates because you can only backdate cancer by one year with the use of mammography. Breast cancer takes a long time to develop and cancer detection by mammography occurs not earlier than in year 8 or 9 in the progression of this disease; hardly an early detection by any standard.  There is definitely a need to develop and use other available technologies to identify breast cancer much earlier. 

I have been advocating the use of breast thermography in conjunction with other screening modalities for many years now. Breast thermography is not a stand-alone screening test for breast cancer and should never be used on its own. However, breast thermography can provide us with a very early sign of breast abnormalities that can lead to breast cancer. An abnormal breast thermography image is the single most important marker of high risk for developing breast cancer. In my view, it would be more beneficial and far more economical to use breast thermography to identify a high-risk group of women that will need additional testing and higher levels of conventional follow up.  This group can be additionally screened using frequent breast examinations, regular hormone testing, other biomarkers associated with high risk for breast cancer, along with ultrasound and diagnostic mammography when necessary. 

There is no need to settle for existing problems using mass screening mammography that at best appears to be ineffective and at worst downright harmful. Many will say that mammography is not perfect but this is the only test that we have available and no matter the problems associated with mammography screening, the benefits outweigh the problems. Clearly this is no longer the case and it never was. This belief system is outdated and needs to change based on scientific evidence presented. It is imperative to rethink our approach to breast cancer and use all available technologies appropriately. If we seriously want to save lives,  we need to incorporate the use of breast thermography as another useful marker in breast cancer detection and prevention plan.