Shopping at my local pharmacy last week, I was taken aback by a product on the counter: “Self check breast cream”. In large font was the message “self checking your breasts is important”.

This is a fairly familiar message. But is it true? The evidence is surprisingly complicated.

Breast cancer screening

Breast cancer is a common and important disease. Affecting about one in eight women at some point in their lives, it is the second most common cause of cancer death in Australian women. I’ve seen it profoundly affect many people, including several of my general practice patients. Preventing this would be wonderful.(Watch: How to check your breasts. Post continues after video.)

Cancer screening means looking for cancer in people without symptoms. An established (though still controversial) example is mammography: breast X-rays. Another less established method is breast self-examination.

At first glance, being offered a chance of finding cancer early sounds like a good thing. But it’s more complicated than that. Some screening tests, despite good intentions, fail to help, or even cause harm.

There are various ways screening can mislead us. Screen-detected cancers often show better survival rates than other cancers, but this doesn’t mean the screening is saving lives.

It can instead mean we’re just detecting the cancer earlier without changing its course, or that the screening is picking up some so-called “cancers” that would never have caused symptoms (this is called “overdiagnosis”).(Post continues after gallery.)

Melissa Etheridge

Suzanne Somers

Marissa Jaret Winokur

Joan Lunden

Wanda Sykes

Dame Maggie Smith

Jaclyn Smith

Screening can also cause problems by raising false alarm – discovering a lump that resembles possible cancer, but after a worrisome round of tests turns out not to be.

To best measure the effect of a screening program, we need large “randomised controlled trials” of screening. These are studies in which people are randomly allocated to either screening or normal care, and followed over time to see what happens.

The paradox of breast self-examination

Two large trials of breast self-examination measured important outcomes such as harms and death. In these trials, study staff taught groups of women how to examine their own breasts in a careful, structured manner. Monthly self-examination was encouraged.

These women were followed up and compared to other women who had no training or encouragement in self-examination.

The results of these studies have been brought together and meta-analysed (mathematically combined) in order to summarise our best evidence on the effectiveness of self-examination.

The combined results from nearly 400,000 women are disappointing: encouraging women to examine their own breasts does not prevent any deaths from breast cancer, but does cause false alarm and an increase in the need for biopsies (involving needles or surgical excision).

Image: iStock

But here’s the apparent paradox: despite this lack of effectiveness of breast self-examination in these trials, most breast cancers are still discovered because women notice a change in their breasts.

Trying to put these seemingly contradictory facts together can be headache-inducing. How can this all be true?

It must be that significant breast cancers are likely to be detected spontaneously or accidentally by women in the course of normal life, even without self-examination. Adding structured, monthly self-examination sounds wise, even noble, but sadly our best evidence finds it is unhelpful and leads to false alarm.

Why the false alarm? Because it’s normal for breasts to be a little bit lumpy, as firmer glandular breast tissue sits suspended amongst looser fatty tissue. Picking the “signal” of cancer from the “noise” of normal lumpiness can be tricky.

So what should we do?

Authors of breast cancer guidelines have tried to resolve the apparent paradox. They recog