How is the Oncotype DX Assay USed in Planning the Treatment for Patients with DCIS?
Let me share with you some thoughts on that subject.
The Oncotype DX assay has been available now for several years.
We use it in women who are estrogen receptor positive with either invasive ductal carcinoma
or invasive lobular carcinoma.
But what actually has been needed for a long period of time is a very similar assay for
patients who have in situ breast cancer, known as DCIS.
The folks at Genomic Health have modified the original 21 gene assay, now with what's
called a different algorithm to create an Oncotype DX score for patients with DCIS.
Now this score, the recurrence score, is on a scale from 0-100, like the invasive assay,
but it does something really unique.
On your screen right now is the results of a patient who has an Oncotype DX score of
6.
On the left hand side of your screen you see a calculation of the local events.
In other words, what are the chances of the cancer recurring in the treated breast?
This is of course in patients who have had lumpectomy.
And could that recurrence be either in situ or invasive breast cancer?
The curve that you see going up is a curve of the increasing biology of in situ breast
cancer.
The higher the curve goes up, the more potentially aggressive the DCIS is.
Just like with the invasive cancer, we get a low risk recurrence score, an intermediate
risk recurrence score, and a high risk recurrence score.
On the right hand side of this report is a calculation for an invasive breast cancer
event within the treated breast.
Again, this is in patients who have had lumpectomy.
The calculation is then made -- over the next ten years, what are the chances of the cancer
not only coming back as in situ cancer, but potentially more aggressively as an invasive
cancer.
I've got up on the screen a recurrence score of 6.
This is actually one of my own patients, a 57 year old woman, who had a small 5 mm low
grade ductal carcinoma in situ.
As you can see, the recurrence score came back a 6.
Referring to our chart, this means that over the next ten years, she has approximately
a ten percent chance of either a recurrence of in situ breast cancer or invasive breast
cancer.
On the right hand graph, she has only a four percent chance of an invasive recurrence.
This is an extremely low score.
Combining this low score with the fact that the cancer was quite small, this patient chose
not only to not choose radiation therapy, but also not to go on anti-hormonal therapy.
The validation study that was done to show that this test has validity, was a prospective
trial of women with ductal carcinoma in situ.
But there were limitations placed in this validation study.
The in situ breast cancer had to be 2.5 cm or smaller in size, and the rim of normal
tissue around the in situ breast cancer tissue had to be at least 3 mm.
The validation study did not take into account the grade of the in situ breast cancer.
In situ breast cancers can have 3 grades: low grade, intermediate grade, and high grade.
The low grade in situ breast cancers act extremely benignly, in other words, not very aggressively
at all.
Conversely, the high grade in situ breast cancers can act very aggressively, and may
have within them areas of associated invasive cancers.
In blending in this score into how we make decisions about patients with in situ breast
cancer, we have to take into account multiple factors.
How big was the in situ breast cancer?
What were the margins like?
What was the grade?
All of these factor together.
Couple that with a recurrence score assay like my patient, and I believe that my patient
was treated absolutely appropriately with no need for radiation therapy, no need for
tamoxifen or any other form of anti estrogen therapy.
Recently, I was sent a question at BreastCancerAnswers.com about a DCIS recurrence score of 19.
In general, we don't comment on specific questions asked to us at BCA, but I thought I would
blend in a response with a recurrence score of 19 into the graph that I've been showing
you.
The calculations for any kind of event in the treated breast with a recurrence score
of 19 is approximately 13 percent, or a little higher than the recurrence score of 6.
As the score goes up, the actual increase in the events in the low risk group is actually
quite small.
And also, within the chances for the recurrence score of 19 of being over here with an invasive
occurrence calculated out to only 5 percent.
The bottom line here is that a low risk score is a low risk score.
Many of these patients in the future are not going to require adjuvant radiation therapy.
I am putting this assay into use in my practice more and more.
This gives us some additional information about what the biology of the in situ breast
cancer is like.
Just like with invasive cancers, the biology of in situ breast cancers is highly variable.
I believe that an oncotype recurrence score assay is going to be an important tool in
helping us make bottom line decisions about how best to treat patients
with DCIS.