Using known risk factors for breast cancer,
mathematical models can be developed to help answer important
questions. These mathematical models are useful tools for researchers
and for patients as follows:
- 1. Research on risk factors
- The Claus risk assessment model was used to discover the
subpopulation of people who had an autosomal dominant genetic allele
that increased their risk from 10% to 92%. This led to the discovery of
the BRCA genes associated with breast, ovarian, and prostate cancer.
- 2. Clinical trial eligibility
- The Gail risk assessment model was developed to help researchers
determine who to enroll in the NSAPB Breast Cancer Prevention Trials
where chemoprevention was shown to reduce breast
cancer risk.
- 3. Guidelines for doing BRCA
testing - BRCA testing is very expensive and practically
worthless if done on everyone (because it is so rare to be homozygous
for BRCA1 or BRCA2). Mathematical models such as the BRCAPRO, BOADICEA,
and Tyrer-Cuzick models can help determine what patients should undergo
BRCA testing. The decision for testing is usually made when one of
these models predicts a 10% or greater chance that there is a mutation
of the BRCA1, BRCA2, or both genes.
- 4. Guidelines for doing MRI
screening for breast cancer - MRI screening for breast
cancer is not a cost effective screening test for the general
population, but in specific groups, there are clear cut reasons to do
so. In general, screening MRI is recommended for women with 20-25% or
greater lifetime risk of breast cancer. The BRCAPRO and Tyrer-Cuzick
models have been used to help make clinical decisions about ordering
MRIs for breast cancer screening.
- 5. Guidelines for breast cancer
therapy - The Gail model is used clinically to help
determine who should be put on tamoxifen or
raloxifene for chemoprevention. Other models have been used to help
make decisions about breast cancer risk reduction with prophylactic
mastectomy.
For these reasons, it is important to understand
these models. These models are collectively refered to as "risk
assessment tools". The following paragraphs summarize the most popular
and most widely used risk assessment tools. Keep in mind that none of
these risk assessment tools apply to breast cancer survivors. No
mathematical model has been widely accepted to determine cancer risk in
cancer survivors.
General Risk Assessment
Tools
Gail Model:
The Gail model is a validated risk-assessment model that focuses
primarily on nonhereditary risk factors, with limited information on
family history. It was developed by scientists at the National Cancer
Institute and the National Surgical Adjuvant Breast and Bowel Project
(NSABP) to assist health care providers in discussing breast cancer
risk to determine their eligibility for the Breast Cancer Prevention
Trial. The tool allows one to project a woman's individual estimate of
breast cancer risk over a five-year period of time and over her
lifetime. It also compares the woman's risk calculation with the
average risk for a woman of the same age. The Gail Model is an on-line
quiz that has 13 questions and is interactive. This calculator is based
on published risk statistics and methods gathered from peer-reviewed
journals, and has been extensively tested for its validity.
The major limitation of the Gail model is the
inclusion of only first-degree relatives, which results in
underestimating risk in the 50% of families with cancer in the paternal
lineage and also takes no account of the age of onset of breast cancer.
It may underestimate risk in certain groups, such as obese patients.
National Cancer Institute
Model: The NCI
risk assessment tool is essentially a simplified Gail Model that also
factors in race. Race is a factor in determining breast cancer risk but
is excluded when determining eligibility for clinical trials. This tool
is probably the most popular risk assessment tool available to the
public as an on-line, interactive risk calculator. The on-line quiz is
a shorter, nine-point questionnaire that includes multiple factors,
giving a woman her future five-year risk of breast cancer and her
lifetime risk of breast cancer.
The NCI tool does not account for a lot of risk
factors that can be modified. For this reason, it is difficult to use
this test as a motivation tool to show people how lifestyle can alter
their risk of breast cancer. It also cannot be used in breast cancer
survivors, in patients with DCIS, LCIS, or people who carry one of the
BRCA genes.
BRCAPRO model:
This is a statistical model available as a computer program that uses
two different algorithms to evaluate family history and helps a doctor
determine the likelihood of finding either a BRCA1 mutation or a BRCA2
mutation in a family. The results of this can be used to determine if
BRCA testing is indicated. This is very useful in light of the high
cost of BRCA testing ($3,000). None of the nonhereditary risk factors
can yet be incorporated into the model, however. In a comparison of
four different methods for estimating breast cancer risk in patients
with a family history of breast cancer, the BRCAPRO model was the least
accurate. It predicted only 49% of the breast cancers that actually
occurred in the screened group of patients with a family history of
breast cancer.
Harvard
Center for Cancer
Prevention Risk Assessment Tool: This is
another breast cancer risk assessment tool that includes more lifestyle
factors than the NCI or Gail Model tools. It has not been studied as
extensively as the Gail Model or the simplified NCI model, but it is
promising in that it includes many lifestyle factors that people can do
to modify their risk of developing cancer. It is also an on-line
questionnaire that can be used by both women and men to estimate their
breast cancer risk.
Making all this practical
Now after a thorough and confusing discussion of
all these statistical models, it's time to make all this information
practical. What is the best way to help a patient accurately assess her
risk of breast cancer and if possible, show her what positive factors
are reducing her risk and what negative factors can be changed to
reduce her risk? If possible, it would also be great to show the
patient the value and indications for testing, imaging,
chemoprevention, and in some cases surgery. A discussion of the
practical aspect of each of these is addressed in a Q & A
format below:
Q: What (free) online programs can
be used to help a patient assess their risk of breast cancer?
A: Several of the
risk assessment tools mentioned above can be accessed for free by the
public. Here are the tests and their websites:
This is a great interactive questionnaire that
calculates five-year and lifetime risk of breast cancer developed by
the Harvard Center for Cancer Prevention and made public online in
2000. In 2005, they launched the Spanish version of the site, "Cuidar
de su Salud". The risk calculator includes lifestyle factors such as
weight, dietary vegetables, alcohol intake, as well as Jewish
ethnicity. It does not include other ethnicities, however, and is not
accurate for BRCA mutation carriers or breast cancer survivors. Despite
these issues, this is by far the best free online risk calculator since
it is very interactive and gives you a personalized description of your
risk in the form of a colored bar graph, which they can electronically
manipulate to experience "virtual" risk reduction. The bar graph is a
seven-level scale that compares users to a typical man or woman your
age. Users learn where to focus their prevention efforts and how to
make lifestyle changes by "clicking on" personalized strategies. With
each click, the bar graph shrinks, and the user watches his/her
predicted risk drop. This is a great concept to motivate people to
participate and comply with lifestyle modification measures.
- 2. The NCI Risk Assessment Tool
-regular
web: http://www.cancer.gov/bcrisktool
This is the easy to
use, on-line questionnaire based on a modified Gail model that also
includes ethnicity. It does not factor in a personal history of breast
cancer, DCIS, or LCIS. It does not account for other factors such as
BRCA status, hormonal replacement therapy, lifestyle factors, breast
feeding, menopause, or mammographic density. Despite these issues, it
is a very useful tool that gives a woman her five-year and lifetime
risk of breast cancer. It is the only risk assessment tool that can be
used via mobile handheld devices (any type). A version of this can be
downloaded for PDAs with Windows Pocket PC operating system as well.
Q: What programs can be used to help
a doctor make decisions about ordering a breast MRI?
A: The American
Cancer Society has developed some very good guidelines for breast
cancer screening with MRI. It should be emphasized that MRI is an
adjunct to mammography, not a replacement.
Article Source: http://
www.articlesbase.com/womens-health-articles/how-to-calculate-
your-risk-for-breast-cancer-795965.html About the Author
Dr. Mai Brooks is a surgical oncologist/general
surgeon, with expertise in early detection and prevention of cancer.
More at www.drbrooksmd.com, thecancerexperience.wordpress.com and
progressreportoncancer.wordpress.com. | 