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A recent study sought to add some evidence to the usefulness of breast cancer screening by looking at the stage and type of cancer.
All women over the age of 50 in Ontario, Canada are advised to undergo routine breast cancer screening. In recent years, some researchers have questioned the usefulness of breast cancer screening.
Breast cancer screening has not reduced diagnoses
These researchers have two main arguments. The first is that breast cancer screening can produce a false diagnosis of cancer in one-third of all women diagnosed. The second is that breast cancer screening has not reduced the number of women diagnosed with late-stage breast cancer.
Breast cancer screening involves having a mammogram, which is an x-ray of the breast tissue. The purpose of the mammogram is to detect breast cancer at an earlier stage than the patient or doctor could do otherwise. The hope is that treating cancer at an early stage increases the likelihood of a cure.
How useful is breast cancer screening at detecting early-stage cancer?
An Ontario-based group of researchers asked how useful breast cancer screening actually is at detecting cancer at an early stage. They hoped that their research would also provide some answers as to why it is that cancers are still not being caught at an early stage in women who undergo breast cancer screening. Their results were published in the Journal of Cancer Research and Clinical Oncology.
The stage of breast cancer at the time of breast cancer screening was compared with the stage of breast cancer at the time of a lump becoming obvious.
It is not only the stage at which breast cancer is caught that is important for a cure. The type of breast cancer is important too – some types are more aggressive than others, making a cure less likely. Therefore, the type of breast cancer that was found through breast cancer screening and through finding a lump was also compared.
Results from 2882 women diagnosed with breast cancer, over a period of four years were analyzed. All women had had a mammogram with the Ontario Breast Screening Program within 28 months of the breast cancer diagnosis. Of these women, 1091 developed cancer that was not initially picked up on from the mammogram.
Breast cancer screening is still worthwhile, but aggressive cancers may benefit from different screening programs
The researchers found that in the women where the mammogram failed to pick up on cancer, the cancer type was more aggressive. They speculate that the reason for this is likely that these tumors are fast-growing and developed after the normal mammogram was seen. They discuss that this may help explain why breast cancer screening is done every two years has not reduced the number of patients diagnosed with a late-stage breast cancer.
The cancers that were detected by screening were three times more likely to be early-stage cancers. This was true of both aggressive and non-aggressive types of cancer.
The researchers conclude that breast cancer screening remains worthwhile. However, fast-growing aggressive cancers may be better diagnosed by changing the screening programs and identifying patients who are at higher risk of developing more aggressive types of breast cancer.
Written by Nicola Cribb, VetMB DVSc Dip.ACVS
Reference: Holloway C, Jiang L, Whitehead M, Racz J, Groome P. Organized screening detects breast cancer at earlier stage regardless of molecular phenotype. J Cancer Res Clin. 2018:1–7. doi:10.1007/s00432-018-2687-4.