Medicare-funded MRI breast screening of high risk women under 50 years is poorly targeted, a WA study suggests.

The study compared the MRI screen-detected cancer prevalence in Medicare-eligible high risk women due to family history or genetic mutation, women undergoing MRI staging for cancer in a contralateral breast and women undergoing surveillance due to prior breast cancer or high-risk lesions. 

The study comprised 870 MRI studies in 471 women at the Sir Charles Gairdner Hospital between 2015 and 2017.

It found the cancer prevalence was highest in women having MRI staging for cancer (600/10,000) compared to those undergoing surveillance (116/10,000) and the Medicare-eligible women (77/10,000).

Contralateral breast assessment sensitivity was 83% compared to 100% in the surveillance group and just 50% in the screening group. 

The study authors said their findings showed a lower than expected cancer detection rate for a high-risk population, but one which was still above that for the general population. 

“These data made us question the eligibility criteria for Medicare rebate-eligible high-risk breast cancer MRI screening,” they wrote in the Journal of Medical Imaging and Radiation Oncology. 

“However, staging MRI for breast cancer as a non-billable study contributed to patient care. In assessing the contralateral breast at staging breast MRI, we found a substantial proportion of MRI-detected breast cancers, which were occult at initial 2D screening mammography (double read) and diagnostic staging bilateral breast ultrasound.”

The study noted that some of the women initially categorised as high-risk according to the Medicare eligibility criteria were subsequently reassessed as at a lower risk. Therefore a more formal risk assessment was warranted.

“Prior to committing a woman to many years of high-risk screening, in some cases 25 years of MR screening, with its concomitant risk of gadolinium exposure and increased biopsy rates, genetic testing and counselling is recommended.”

In conclusion, they said the MR464 Medicare rebate schedule did not select the women with the highest risk of breast cancer diagnosis.

However lead author and radiologist Dr Glen Lo told the limbic the findings need confirmation from audit at other sites.

“This is a very small sample size study in a single institution for a short duration of only 3 years – the confidence intervals are wide for estimated screening performance,” he said.

He also added it was not a cost effectiveness study.