Your next mammogram could be even more of a lifesaver

• The FDA has implemented a new rule for mammograms to spot hidden cancers.
• As of September 10, mammogram reports should flag high breast density.

Mammograms conducted in the US will now screen for breast density.

The new rule, effective September 10, is a major step that could help detect hidden cancers.

Half of women over the age of 40 have dense breasts. Higher breast density increases your risk of developing breast cancer. It also makes it harder for clinicians to spot cancer in a mammogram.

In cases of high breast density, other screening methods, like ultrasounds or MRIs, can be more effective at detecting tumors.

Patients and doctors have been campaigning for decades to include breast density in screenings, testifying to the US Food and Drug Administration (FDA) and lawmakers. Their campaign culminated in a meeting at the FDA this summer, and a new rule.

Why breast density makes cancer more likely and harder to spot

The new rule means that mammogram reports will now assess the ratio of fatty tissue to fibroglandular tissue. More fibroglandular tissue means a denser breast.

Dense breasts obscure tumors on a mammogram because the fibroglandular tissue — like cancer — looks white on the screen. Fatty tissue, meanwhile, appears black, gray, or colorless.

A higher breast density also increases one's risk of developing breast cancer, though it's not exactly clear why.

The new rule does not mandate specific follow-ups or next steps, but providers should advise patients with dense breasts to explore further screening.

A woman whose breast cancer went undetected spent years campaigning for this rule

Earlier this year, JoAnn Pushkin, the executive director of the educational resource DenseBreast-info, shared her late cancer diagnosis story with Business Insider.

Pushkin had no apparent breast cancer risk factors. Her only family history was one aunt who'd had breast cancer. She regularly exercised, ate well, performed self-exams, and had mammograms every year after she turned 40, the recommended age to start screening.

Although all her mammograms came back clear, at 45 she felt a lump in her breast. She went for a scan and a biopsy, and was told she had later-stage breast cancer. A follow-up mammogram still showed no signs of cancer. That's when her doctor explained she had dense breasts, making the cancer almost impossible to spot on a mammogram (though it came up in an ultrasound).

Pushkin needed a double mastectomy, seven surgeries, and eight rounds of chemotherapy. She went into remission, but her cancer returned. She then had another 30 rounds of radiation.

Now in her 60s, Pushkin says she still has to be vigilant, getting screened for recurrences and treating side effects.

She is celebrating the new FDA rule, though she laments that it didn't come sooner as many of her fellow activists have died from cancers that went undetected.

"Some of them were fighting for these laws literally while sitting in chemo chairs, getting infusions while they're fighting for these laws," Pushkin told BI.

"When you think about the fact that these 39 state laws were fought for by sick women, it is quite something that these women and their families have paid the price for this," she said.