SB 1538 would require that following a mammogram, women with dense breast tissue are informed that dense breast tissue can obscure abnormalities on a mammogram, and that they may wish to discuss the potential value of additional screening with their doctors, Simitian said.

The bill passed the Senate by unanimous vote; the legislation now heads to the California Assembly.

Gov. Jerry Brown vetoed a similar bill in October of last year. Since then, Virginia has joined the list of states with breast density notification laws, and two separate studies from the first year of a similar law's implementation in Connecticut have shown a 100% increase in breast cancer detection rates in women with dense breast tissue who had supplementary screenings, according to Simitian's statement.

"My hope is that we can get to 'yes' this year and that we can begin saving lives as soon as possible," he said. "This bill simply requires that information that is already shared between doctors also be shared with a patient herself. This is about a patient's right to know. It is about giving patients the information they need to be effective advocates for their own health."