Women with stage IV breast cancer detected through screening have a 60% chance of survival ten years after diagnosis.

This is in comparison to a survival rate of under 20% of those with stage IV breast cancer which was not detected through screening.

The study by King’s College London, Queen Mary University London, and the University of Southern Denmark, aimed to find out if the method by which breast cancer is detected impacts survival rates at different stages of the cancer.

These results, published in JNCI, suggest that even at the most serious stage of the disease, where cancer has spread from its original site to distant organs or tissues in the body, screening may not have come too late to treat successfully.

The study found that cancers diagnosed by screening at this stage had a greater likelihood of surgical intervention.

This suggests that although they had spread, that spread was limited and complete surgical removal could be attempted.

Breast cancer screening programmes provide women with national access to mammograms, which are X-rays that looks for cancers that have not yet led to symptoms.

This is then followed by a diagnostic assessment for abnormal screens.

However, so far there have been limited studies which have examined survival differences stage-for-stage by screening status.

Dr Amy Tickle, the lead author who undertook the research whilst doing a PhD at King’s College London, said:

“Our results show that how breast cancer is detected could impact the patient’s survival chances. There is understandably a lot of fear around cancer being found late, but our findings provide reassurance that long-term survival is still possible when it is found during screening. Our research highlights the importance of screening programmes and we hope this encourages everyone who is invited to attend their appointment. Further research is now needed to better understand the reasons behind this improved survival.”

To do this the researchers linked Danish breast screening records between 2010 and 2019 with national death records from 2010 and 2022.

They then compared the mortality in women with breast cancer with that in women without breast cancer to estimate the excess mortality resulting from the cancer.

Uniquely mortality in women without breast cancer was looked at separately for women depending on their prior breast screening history.

This removed biases associated with breast screening participation.

Professor Peter Sasieni, Dr Tickle’s PhD supervisor at King’s College London, who now works at Queen Mary University of London, said: “We looked at survival in women with screened detected breast cancer, in women who had never been screening and in women who had been screened previously but whose cancer was not detected through screening. For women with Stages I, II and III breast cancer, survival did not vary by screening history. But for stage IV breast cancer, we were surprised to see that prognosis for those whose cancer was screened detected resembled that of women with stage III breast cancer – they were three times more likely to live for another 10 years than other women with stage IV breast cancer.”

In the UK, the NHS offers breast cancer screening (mammograms) to women aged 50 to 70 every three years to detect early signs of cancer.

Invitations are sent automatically to those registered with a GP, with the first appointment usually by age 53.

These new findings highlight the importance of promoting screening.

The authors suggest that they also enable the monitoring of breast screening programmes through predicting the impact on breast cancer mortality by tracking the stage at diagnosis.

In this way we can tell whether changes to breast screening are working 5-10 years sooner than if we had to wait to observe breast cancer mortality.

Source: King's College London