The legislation could help save thousands of lives through earlier detection of cancer that might be obscured by the thickened tissue, health professionals from El Camino Hospital said during a press conference with Simitian today.
Senate Bill 1538 requires that a woman receive information about her breast density on her federally required mammography report if she has dense breast tissue.
Researchers have known since the 1970s that breast density is an indicator of risk for breast cancer, according to Simitian's office. Forty percent of women who get a mammogram have dense breast tissue, but a May 2010 national survey by Harris Interactive found that 95 percent of women do not know if they have dense breast tissue.
Breast density is perhaps the strongest but least recognized risk factor for breast cancer, according to National Cancer Institute studies. Women with extremely dense breast tissue are at four to six times greater risk for developing breast cancer compared with women of the same age and health.
Simitian's bill allows women to be informed of their condition and that breast tissue is associated with an increased risk of breast cancer. The law requires that women be notified that there are additional screening methods beyond mammograms that could detect cancers not found by mammography. The main cause of false-negative results in mammograms is high breast density, according to the National Cancer Institute.
The importance of further screening in women with high breast density was underscored by a January 2011 Mayo Clinic study, which found that in women with significant density of breast tissue, 75 percent of cancer is missed by mammography alone.
Because dense breast tissue appears white on a mammogram, and cancer also appears white, it can be very difficult to detect malignancy, El Camino health professionals said.
"It's like finding a snowball in a snowstorm. It's white on white," said Barb Dehn, nurse practitioner at Women Physicians Ob/Gyn Medical Group at El Camino Hospital in Mountain View.
Simitian, who is now a Santa Clara County supervisor after being termed out in the Senate, first introduced a bill on the subject in 2011, but it was vetoed by Gov. Jerry Brown. Simitian reintroduced a reworded bill, SB 1538 in March 2012.
The idea came from Santa Cruz nurse and breast cancer survivor Amy Colton, who suggested the legislation through Simitian's "There Oughta Be A Law" contest. Colton said she was shocked when she was told she had breast cancer after years of normal mammograms. She learned that she has dense breast tissue only after her cancer treatment.
Federal law requires radiologists performing a mammogram to send a report to the referring physician that included information about a patient's breast density. Radiologists are required to write the patient to inform her of the results of the mammogram, but they are not required to inform the patient if she has dense breast tissue.
Simitian's legislation is based on a 2009 Connecticut law. Recently published research found a 100 percent increase in early breast cancer detection in women with dense breast tissue since the law was in force.
Since the Connecticut law was enacted Texas and Virginia have passed similar laws, and 15 other states currently have similar legislation pending, Simitian's office noted. California's law requires women with dense breast tissue be informed that:
• They have dense breast tissue.
• Dense breast tissue can make it harder to evaluate the results of a mammogram.
• Dense breast tissue is associated with an increased risk of breast cancer.
• Information about breast density will be given to discuss with their doctor.
• Other screening options are available.
Women whose breasts are found to be dense on mammograms can be checked with other procedures that are more likely to detect cancer, such as ultrasound, magnetic resonance imaging (MRI) and screening for genetic disorders, Dehn said.
El Camino Hospital has been giving women the option of whole-breast ultrasounds, which have picked up cancers that might not have been found until two years later, she said.
Dr. Imtiaz Qureshi, medical director of imaging services at El Camino Hospital, said breast density is measured at four different levels, known as BI-RADS. Women with levels three and four have the highest density and are at the highest risk for developing breast cancer or for having their breast cancer go undetected on mammograms.
"There are a lot of subtle findings that are difficult to see, particularly subtle calcification of the tissue that could be an early sign of breast cancer," he said.
In anticipation of the law, El Camino changed its policies starting about five months ago, notifying patients who have dense breasts and offering more supplemental screening, such as ultrasound, he said.
Simitian said that during legislative discussions he pointed out early detection costs a fraction of the cost of later treating a woman with breast cancer. Later treatment is "10 to 15 times greater," he said.
The bill met with opposition from some medical professionals who did not want their judgment to be regulated and who balked at the costs of additional screening. Some detractors, including Brown, initially feared that such a bill could lead to unnecessary anxiety.
But Simitian said he is gratified that doctors are now required to share this information with patients.
"By requiring information on dense breast tissue, the law now ensures that women are better informed about their bodies and will help them make better decisions about the medical screening or care they might need," he said.
"In addition, those concerned about women's health should continue to do all they can to make women aware of this issue, to encourage them to ask the right questions about their cancer risk and about appropriate preventative measures," he said.
Simitian will hold a telephone "Town Hall" about the issue of early detection and the importance of the new law on April 7. Participants can call (866) 476-7782.
More information about SB 1538, is available at senatorsimitian.com by clicking on the "Are You Dense" icon. Additional information about dense breast tissue is available at areyoudense.org.