Proceedings of the Standing Senate Committee on
Social Affairs, Science and Technology
Issue 42 - Twenty-fifth Report of the Committee
Tuesday, June 11, 2013
The Standing Senate Committee on Social Affairs, Science and Technology has the honour to table its
TWENTY-FIFTH REPORT
Your committee, to which was referred the subject matter of Bill C-314, An Act respecting the awareness of screening among women with dense breast tissue, in obedience to the order of reference of Thursday, February 28, 2013, has examined the said subject matter and now reports as follows:
Introduction
Breast density refers to the proportion of glandular and connective tissue, which are higher density, relative to fatty tissue, which has a lower density. Traditional mammography, which uses low dose X-ray imaging, does not effectively distinguish between tumour growth and dense breast tissue because both appear white on mammograms. Effective cancer screening is therefore more challenging among women with dense breast tissue than among those with less dense tissue. Briefly, Bill C-314 would require that the federal government encourage existing agencies and programs to increase awareness of the challenges associated with cancer screening in women with dense breast tissue by identifying information gaps, identifying approaches for better provision of information to women, and sharing information about the identification of dense breast tissue during screening and whether there are follow-up measures to be taken.
Summary of Testimony
During its hearings on the subject matter of Bill C-314, the Breast Density Awareness Act, your committee heard testimony both for and against the content being included in the proposed legislation. Below is a summary of that testimony.
Breast cancer is the most common form of cancer among women. One in nine women will develop breast cancer during her lifetime, while one in 29 will die from it. Early detection is one of the primary factors in determining survival prognosis. To this end, routine breast screening was introduced in Canada in 1988 and now all provinces and territories have organized programs with the exception of Nunavut. These programs were introduced based on evidence that if 70% of women are routinely screened, mortality from breast cancer can be reduced by 25-30%. Since 1990, the mortality rate has fallen over 35%, attributable not only to early detection but also to improved treatment. Mortality from breast cancer is currently 21%, or about 5,200 women in 2012, but may be lower than 5% in those instances where cancer growth is detected early and the tumour is less than one centimetre in diameter. Research has shown that there is no increased mortality from breast cancer among women with dense breast tissue over those with less dense breast tissue. Some witnesses emphasized that all breast cancer screening programs have their own protocols in place with respect to dense breast tissue and that these protocols have to take into consideration the particular resources of the jurisdiction. The British Columbia program, for example, will send women with dense breast tissue for additional screening if they also have another risk factor such as a close family member with breast cancer.
Representatives from the Public Health Agency of Canada, the Canadian Institutes of Health Research as well as Health Canada discussed their roles as the federal government stakeholders in breast cancer screening, surveillance and research. The Public Health Agency of Canada representative stated that the federal government is dedicated to ensuring that women can make informed decisions about their care. To that end, your committee was told that, with respect to breast cancer, the federal government continues to invest in research, surveillance and monitoring, and information sharing: activities that support raising awareness and early detection of breast cancer.
The Public Health Agency of Canada indicated that it uses existing programs in order to better inform women about the issues associated with dense breast tissue and identify information gaps that require further investigation. It further explained that the federal government's investment in the Canadian Partnership Against Cancer ("Partnership"), which implements the Canadian Strategy for Cancer Control, is the primary means by which it is taking action on cancer. Your committee was told that new knowledge and its implementation into practice is facilitated through the Partnership and the collaborative work it undertakes with groups and agencies across Canada. Specific to breast cancer, the Partnership supports the Canadian Breast Cancer Screening Initiative ("Initiative"). Your committee was told that the Initiative is responsible for measuring the performance of breast screening programs across Canada. It facilitates the sharing of information and best practices across programs, and it provides the forum for experts to discuss the challenges that have been raised. Members were told that it also maintains a database that contains information and statistics from the provincial and territorial breast screening programs. Representatives from the Breast Screening Program of British Columbia provided your committee with information about the program it administers. They also told your committee that there is generally a high rate of participation of Canadian women in breast cancer screening programs across the country.
The Canadian Institutes of Health Research (CIHR) described its role as a funder of research. Witnesses emphasized that the federal government's continued investment in research addresses knowledge gaps related to breast cancer including issues specific to dense breast tissue. Members were told that CIHR awarded $110 million over the last five years to breast cancer research, of which $25 million was awarded in 2011-2012, including multiple studies specifically focussed on breast density. Breast density research funded by CIHR has revealed that it is a risk factor for breast cancer, preceded only by age and genetic factors. Your committee heard that research has also determined that hormone replacement therapy and some environmental and lifestyle factors are associated with breast cancer risk. Other research currently funded in Canada by CIHR involves the evaluation of alternative optical techniques since there are challenges associated with interpreting mammograms of breasts with dense tissue.
Health Canada, as the regulator of medical devices, indicated that it is responsible for licensing the equipment used for breast cancer screening. Your committee was told that licence applications prior to 2000 were primarily for traditional film-screen mammography equipment, between 2000 and 2010 applications were for computed mammography technologies, and since 2010 applications for breast cancer screening equipment have been primarily for digital mammography. Health Canada stated that no other technology has been approved specifically for breast cancer screening.
Your committee also invited women's health advocacy groups including the Canadian Breast Cancer Network, the Canadian Breast Cancer Foundation and the Canadian Women's Health Network to speak to the subject matter of the bill. These groups lauded the attention that this bill proposes to bring to the issue of dense breast tissue and the associated challenges of screening it. In this regard they encouraged any additional efforts that this bill produces to detect cancer in women with dense breast tissue.
Finally, your committee invited radiology professionals and researchers to discuss the challenges of screening for breast cancer in women with dense breast tissue. The Canadian Association of Radiologists indicated that it will be issuing practice guidelines and technical standards for breast imaging soon. It also indicated that its standard for communicating the findings of diagnostic imaging states that reports should address breast tissue density. It was suggested that physicians should interpret and communicate findings of dense breast tissue within the context of other risk factors. A representative of the Clinique Radiologique Audet explained that other technologies can more efficiently distinguish cancer in dense breast tissue than traditional mammography. These technologies include magnetic resonance imaging (MRI), tomosynthesis and ultrasound. Researchers described their role in identifying gaps in information regarding the screening of women with dense breast tissue and producing the evidence to fill these gaps.
Witnesses were clear and their testimony was consistent with respect to describing the challenges of screening dense breast tissue. In addition to the observation that both dense tissue and cancerous growths appear white on mammograms, they also emphasized that assessing tissue density is not standardized and is subject to the interpretation of radiologists. Some witnesses described the BI-RAD System (the Breast Imaging Reporting and Data System) which classifies tissue as 1) fatty, 2) scattered dense, 3) heterogeneously dense, or 4) extremely dense. Witnesses suggested that about 40% of women have either heterogeneously dense or extremely dense breast tissue, the categories specified in Bill C-314.
Some witnesses noted that the role of the federal government in this area is through its investment in the Partnership and CIHR. They suggested that the Partnership is best suited to collect and disseminate new knowledge, raise awareness and provide information to women about breast cancer screening, including issues specific to dense breast tissue. Some witnesses commented on the high quality of the studies funded by CIHR and the valuable new information that has resulted. Witnesses did not raise concerns regarding the level of funding for research dedicated to either breast cancer in general or to breast tissue density specifically, but did encourage continued federal investment.
With respect to the goal of Bill C-314 and the activities proposed therein, a number of witnesses indicated that this work is already within the mandates of the stakeholders identified in the bill and that currently it is being carried out efficiently. Some witnesses suggested that implementation of the clauses of this bill, which, they argued, would impose vague requirements on the federal government generally and on the Canadian Breast Cancer Screening Initiative specifically, could result in mandatory disclosure of breast density information to women following their screening, without any further useful information about follow-up measures. That is, several witnesses emphasized that there is not enough evidence to support additional screening of women with dense breast tissue and they therefore questioned the value of systematically informing women when they are found to have it.
Your committee was told that screening programs are designed for a healthy population. Screening either detects a cancer or confirms the absence of cancer. The interpretation of the subject matter of Bill C-314 by some witnesses was that it could result in a large proportion of women who have been screened and been found to have dense breast tissue either being sent for, or requesting, additional screening. This would be inconsistent with the current mandate of screening programs. Further, if this interpretation is accurate, witnesses cautioned that the dramatic increase in the number of women seeking mammograms would produce long wait times for all women, not just women with dense breast tissue. This delay would lengthen the time to diagnosis and subsequent treatment for women with cancer. Most witnesses noted that extra screening procedures and longer wait times would likely cause additional anxiety for women; however, other witnesses suggested that it is not possible to remove anxiety completely. Your committee also heard that while every woman has the right to know about her breast tissue density it is a different matter to systematically inform all women if they have dense breast tissue whether they want the information or not.
Some witnesses emphasized that, with respect to supplemental screening, alternative imaging options are available that can distinguish cancer growth from dense tissue. Others cautioned that it is premature to advocate using these options as there is insufficient consensus in the research literature that having dense breast tissue alone warrants supplemental screening. They noted that MRI is expensive and is used sparingly for high risk women only, that tomosynthesis exposes the patient to higher levels of radiation than mammography and that although ultrasound can also detect some of the cancers missed by mammography it also produces more false positive results. With respect to the latter, witnesses stated that research indicates that screening by ultrasound results in a rate of false positive results that is four times higher than it is for mammography. That is, women with dense breast tissue who are subjected to supplemental ultrasound screening will obtain one false positive result for every ten performed and be required to undergo an unnecessary biopsy, compared to one in forty women who undergo mammography. This situation would translate into increased anxiety as well as needless biopsies and lumpectomies.
Researchers noted that mammography has continued to evolve over the years and that they had designed digital mammography as a means to overcome the difficulty of detecting breast cancer in dense tissue and that it has been shown to be more accurate than traditional film mammography. Supplemental screening with either tomosynthesis or additional mammography would expose women to even more radiation.
Your committee heard from several witnesses that the 2011 recommendations on screening for breast cancer from the Canadian Task Force on Preventive Health Care should be revisited. They questioned the recommendation that women aged 40-49 years not be routinely screened and pointed out that seven breast cancer screening programs in Canada still offer routine screening to this age group. This 2011 recommendation was described as having come from analysing old data and that more recent data supports routine screening for these women. The upcoming practice guidelines for radiologists will be recommending that this age group be included for annual screening.
Some witnesses questioned whether the content of the bill was drafted in the best interest of all Canadian women or whether it is in the interest of advocates for alternate imaging technology. In this regard, some witnesses questioned the planning and research that went into drafting the bill. When questioned by your committee, witnesses indicated that they had not been consulted on it. In particular, the Canadian Breast Cancer Screening Initiative, which is specifically identified in clause 2(c) of the bill as having a role in information sharing, was not consulted.
Your committee heard from several witnesses that existing programs and organizations are already carrying out the proposed activities and that it would be premature to implement requirements in this area. The bill was also described by these witnesses as unnecessary.
Conclusion
Your committee heard from a majority of witnesses that it is premature to legislate in the area of breast tissue density, and that existing programs and agencies currently carry out the needed activities and are responsive to the evolving knowledge base. While witnesses acknowledged the importance of breast cancer screening, they emphasized that the evidence does not support additional screening based on breast tissue density alone.
Although witnesses recognized the challenges associated with screening women with dense breast tissue, they questioned the role of federal legislation in addressing these challenges.
Respectfully submitted,
KELVIN K. OGILVIE
Chair