- Causes of
- Getting a
- When DCIS
a Second Opinion
Understanding Risk and your Options
Patricia T. Kelly, Ph.D.
St. Francis Memorial Hospital and private Cancer Risk Assessment
practice in Berkeley, CA
Information to help you make informed decisions
Answers to the following questions will help you make decisions
that are right for you:
How does DCIS differ from invasive breast cancer?
One difference is that a DCIS cell lacks the biological capacity to metastasize
or spread to other parts of the body.
What is the size of the DCIS?
Hidden areas of DCIS and invasion are rarely present in the same breast
when DCIS is less than 5 millimeters (1/5 of an inch) in size.
What is the type of DCIS that was found?
This information is one important element in determining the likelihood
that invasive cancer or more DCIS will occur in that breast in the future.
What is the size of the margin (clear tissue containing
no DCIS) around the DCIS?
This is a major element in determining the likelihood that invasive cancer
or more DCIS will occur in that breast in the future.
- What is the chance that invasive cancer or more
DCIS will occur in that breast in the future if I do or do not have:
- More surgery on that breast or a mastectomy?
- Radiation therapy on that breast?
- Tamoxifen treatments?
What is the chance that I will develop DCIS
or an invasive cancer in the other breast?
Factors to consider about the treatment and follow
up decisions you make depend on your understanding of the future risks
associated with DCIS. Risk is not a single measurement, but a complex
of evaluations. Before you make a decision about what treatment advice
to follow, you should understand each of the following five parameters
of risk and how your own diagnosis relates to them. None of these risk
parameters is hard to understand; all it takes is common sense and the
willingness to ask questions.
- Risks Apply to Groups, Not to Each Individual
in a Group
When you learn that a particular treatment provides an advantage of,
for example, 10%, remember that this 10% applies to differences between
the groups in that particular study. It does not mean that
each woman in the treated group received a 10% benefit. Some women in
the treatment group received more than a 10% benefit, some less and
some did not benefit at all.
- What a Risk Refers To
Risks associated with a diagnosis of DCIS almost always refer to the
risk of recurrence in the same breast, the chance that either invasive
breast cancer or more DCIS will occur in that breast at a future time.
Sometimes the risk is for DCIS only, sometimes for invasive disease
only, and sometimes for both combined. Be sure you are clear about what
risk is referred to.
Since DCIS cannot metastasize, NONE of these risks refers to the risk
of death. The type of treatment a woman has mastectomy or not,
radiation therapy or not, tamoxifen treatments or not does not
change her life expectancy after a DCIS diagnosis. In fact, in one study
women diagnosed with DCIS lived longer than women without such a diagnosis,
probably because in that study the women with DCIS had better overall
- Time Frame of the Risk
Risk information without a time frame is not useful or informative.
For example, a 10% risk today is very different from a 10% risk that
is spread over ten years or 100 years.
You may have heard that the average woman's risk of invasive breast
cancer is about 1 in 8 or 12%. This is the risk up to age 80. Of this
12% risk, 2% occurs by age 50. From 50 to 70 the average woman's risk
of breast cancer is 6% and from 70 to 80 it is 4%. The 2% plus 6% plus
4% add up to 12%. As a woman goes through each age without a diagnosis
of breast cancer, she leaves behind the risk associated with it. To
put risk in another context, you are not at risk of being in an accident
on a road you traveled yesterday. You can only be at risk for today's
roads and the roads you'll travel in the years ahead.
The risk of invasive breast cancer increases with age, so the risk in
a given year to a woman in her 70s is higher than the risk in one year
to a woman in her 40s. However, as a woman gets older, her risk to age
80 decreases because there are fewer years left before she will reach
- Margin Size and the Risk of Recurrence
In one study, when the DCIS was small and the margin around it was at
least a little less than half an inch in size, the chance that either
DCIS or invasive breast cancer would recur in that breast was 3% for
women treated with lumpectomy and 4% for women treated with both lumpectomy
and radiation therapy for a period of up to eight years. This shows
that if the margins are sufficient there is actually very little difference;
DCIS is unlikely to reoccur, even without radiation therapy.
- Percent Increase or Decrease
When you hear that one treatment resulted in, for example, a 40% benefit,
remember that such a comparison does not tell you how large this benefit
actually is. For example, if you ask how heavy my dog is, it is not
useful to hear that he weighs 40% more than my grandmother's dog. This
information doesn't tell you what you want to know or how much the dog
actually weighs. If my grandmother's dog is small, a 40% increase means
my dog is moderately heavy. If her dog is large, my dog will weigh quite
a bit. Now let's apply this concept to the risks you might hear about
Tamoxifen Treatments and the Risk of Recurrence
In one study, women with DCIS were treated with lumpectomy and radiation
therapy. Half the group then received tamoxifen for five years and half
the group did not. At five years the group that took tamoxifen had 43%
fewer invasive breast cancers. There were 31% fewer non-invasive breast
cancers (either DCIS or another type of in situ disease called lobular
carcinoma in situ). When presented this way, the decreases in risk to
women who take tamoxifen seem quite substantial.
When these same study results are presented as actual risks, that is,
in terms of how much the dog weighs, their actual size becomes apparent.
The study found that 4% of the women who did not take tamoxifen developed
invasive breast cancer, compared to 2% who took tamoxifen, a 2% difference
spread over five years. For noninvasive disease the difference was 1%.
That's right, the 43% reduction was actually a difference of 2% and
the 31% reduction was an actual difference of 1% in five years!
Tamoxifen Treatments and Risk to the Other Breast
Tamoxifen is sometimes suggested as a way for a woman to reduce the
chance of developing either noninvasive or invasive cancer in the opposite
breast. The study just discussed reported a 52% reduction in risk to
the opposite breast to women with DCIS who took tamoxifen.
Again, the actual risks were much smaller, 3.4% for the group not taking
tamoxifen and 2% for the group that did take tamoxifen. This is a difference
of 1.4% spread over five years. It means that of 100 women followed
for five years, 1.4 more would develop either a noninvasive or an invasive
cancer in the opposite breast if they did not take tamoxifen.
Even these very small differences in risk may not
be due to tamoxifen use, however, because:
- The study included women whose DCIS was not completely
- The study did not examine all of the tissue removed,
so some of the women appear to have had invasive breast cancer, not
By asking questions such as those in the earlier checklist and by having
a clear, commonsense understanding of the risk you face, you will be able
to make informed decisions about treatments for DCIS and are more likely
to feel comfortable about your decisions.