October is Pink Ribbon Month: an annual campaign to increase awareness about breast cancer and get more women screened in order to catch the disease in its early stages, which will boost survival rates.

And as part of the campaign, buildings are lit up in pink and cancer survivors and doctors hold lectures nationwide to get the message out.

But experts in Japan remain divided — and undecided — on one issue surrounding breast cancer screenings and that is whether to tell people who undergo the tests if they have dense breast tissue.

Normal breast tissue is composed of milk glands, milk ducts, fatty tissue and supportive tissue that is dense breast tissue. For those with dense breasts, they have more dense tissue than fatty tissue.

Dense breast tissue shows up white in mammograms and is harder to differentiate from tumors, which also look white. To detect breast cancer among women with dense breasts, some experts recommend an ultrasound scan.

The problem is, many Japanese women — especially younger ones — are believed to have dense breasts, which means mammography tests — the only method endorsed for government-funded screenings — may not work on them.

What’s worse, most women are not informed about the type of breast tissue they have. When a mammography X-ray shows a woman has dense breasts, she would typically receive a report that simply says that “no abnormalities have been detected.”

Mika Masuda, a 55-year-old medical journalist, has vigorously campaigned over the years for breast density information to be disclosed to women who undergo mammograms. Masuda, who was diagnosed with stage-zero breast cancer in 2006, often gives lectures where she urges women to get tested early.

She says she has encountered many women who wondered why they were diagnosed with advanced-stage breast cancer even though they had undergone regular mammograms.

“I had women telling me directly that, ‘I was getting tested every two years (as recommended by the government), but I still developed advanced-stage cancer that requires me to go through chemotherapy. Why is that?’ ” Masuda said in a recent interview. “I felt so heartbroken for them.”

As she learned about the issues surrounding dense breasts — and how women with such breasts could have tumors go undetected for years even if they take mammograms — Masuda said she became enraged at the experts.

Breast cancer doctors and radiologists who analyze X-ray images have a classification system under which they document the breast tissue composition of every woman they screen. The categories are as follows: almost entirely fatty, meaning the breasts are made up mostly of fat; scattered areas of density, which means some parts of the breasts are dense but the majority is nondense; heterogeneously dense, indicating that some areas are nondense but the majority is dense; and extremely dense, meaning nearly all of the breast tissue is dense.

“Doctors have known this all along,” Masuda said. “They have long known about dense breasts and have classified the density of every breast they examine into four groups. But they never let the patients know.”

In 2013, Masuda set up the nonprofit organization Breast Cancer Imaging Network, which promotes exchanges between patients and medical experts. In 2015, the group invited Nancy Cappello from the United States to give a lecture. Cappello, who was not told that she had dense breast tissue until after she was diagnosed with advanced cancer in 2004, became an advocate for disclosing information on breast density. Thanks to Cappello’s activism, 27 U.S. states now have laws in place that require women to be notified if they have dense breasts (areyoudenseadvocacy.org/dense).

In October 2016, Masuda, together with the leaders of 31 other breast cancer survivor groups across Japan, submitted a request to then-health minister Yasuhisa Shiozaki asking that the ministry revise guidelines on municipal breast cancer screenings so that women are told if they have dense breasts. The groups also asked that the wording on mammogram reports be changed from “no abnormalities detected,” to “difficult to judge.”

The groups also requested that women be advised to consider taking ultrasound tests after weighing their risks and that the state ramp up research on dense breasts, including its prevalence across the population.

Currently there is no nationwide data showing the frequency of dense breasts within the general population, according to research recently presented to a health ministry panel. Ratios recorded at a few sample facilities average about 40 percent.

The ministry panel, which sets the nation’s cancer screening policy, discussed the issue of dense breasts for the first time at a meeting in March, then again in June. But panel members remained divided, and generally cautious, about the idea of universally notifying all women who have taken mammograms about their breast density.

Dr. Yoshio Kasahara, a breast surgeon and member of a working group on the issue set up under the ministry panel, told the meeting in March that it is “premature” to introduce a nationwide notification system, noting that municipal government officials are not ready to field inquiries from women with such breasts and that there is not enough manpower to perform ultrasound scans for all such women.

He also pointed to the lack of scientific evidence to justify the need for ultrasound screenings.

A study called J-START, involving 73,000 women in their 40s, found in November 2015 that a combination of a mammography test and an ultrasound scan was 1.5 times more likely to detect early-stage breast cancer than mammograms alone. But experts say it will take several more years for researchers to determine whether performing mammography and ultrasound tests together are effective at lowering mortality rates — the evidence needed to justify adding ultrasound scans to government-funded screenings.

Notifying women that they have dense breasts while presenting no clear follow-up options would lead to “unnecessary mental burdens,” Kasahara argued.

While debate in the ministry has stalled, some municipalities have started notifying women on their own. In Kawasaki, where more than 40,000 women over the age of 40 undergo city-subsidized mammography tests every two years, doctors in April 2016 started informing women about their breast density. So far, no major confusion has been reported, said Dr. Mamoru Fukuda, a breast surgeon and director of the St. Marianna University Breast & Imaging Center who helped introduce the program.

In their mammogram reports, the city tells the women which of the four breast types they have. It also explains that mammograms cannot detect all tumors, and that cancer is harder to detect for women with extremely dense or heterogeneously dense breasts. If concerned women call the hospitals where they were screened, the hospitals are instructed to tell the women that dense breasts are not an illness, but an ultrasound scan is an option for which they would need to pay the full cost.

“We should promote evidence-based medicine, and it’s true that nobody has proven that an ultrasound test absolutely works to reduce cancer deaths,” Fukuda said by phone. “But whether someone has dense breast is personal information and it should be told to the woman. Withholding such information without any plans to introduce a notification system in the foreseeable future is not a patient-driven policy.”

Fukuda’s breast and imaging center polled 1,064 women who took city-funded or private breast cancer screenings between March 2016 and February 2017. Over a half of the respondents knew nothing about breast density beforehand, but after they read a pamphlet about the issue, 86 percent replied that they wanted to know their own breast density.

Masuda recommends that all women who undergo mammograms in municipal screenings demand that their breast density be disclosed, if it is not disclosed already. “Women in Japan are no fools,” she said. “We are not demanding that ultrasound tests be covered by public insurance. But the case in Kawasaki shows that, by informing the women, they can be more proactive about protecting their health. We have the right to know. It’s about our own body.”

A Matter of Health covers current research, technology and policy issues relating to health in Japan.

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