As more American women are screened for breast cancer with mammograms, doctors are seeing more of a condition called ductal carcinoma in situ (DCIS). Sometimes called a pre-cancer and sometimes Stage 0 breast cancer, DCIS is a non-invasive lesion that is confined within the lining of the milk ducts of the breast that is more benign than a cancerous tumor in that it does not have the ability to invade other parts of the body.
It's estimated that about 55,700 cases of DCIS were diagnosed in the United States in 2003. While some cases of DCIS will go on to become invasive cancers that have the power to travel outside of the breast and become a threat to someone's survival, it's not yet known which cases will become cancerous and which will not. As a result, everyone with DCIS receives treatment. There are concerns, however, that some women are receiving unnecessarily aggressive treatment, such as a mastectomy that is not indicated, and that others, particularly those women who have more aggressive forms of DCIS, might be undertreated with, for example, a lumptectomy without radiation.
Nancy Baxter, MD, PhD, is an assistant professor of surgery in the division of surgical oncology at the University of Minnesota, who conducted a study published last March in the Journal of the National Cancer Institute, which examined trends in the treatment of DCIS between 1992 and 1999. Below, Dr. Baxter explains how DCIS differs from invasive cancer and what the appropriate treatment involves.
What is DCIS?
DCIS is a pre-invasive cancer of the breast, which means that the cells have become cancerous but they have not gained the ability to spread outside of the breast ducts. It's a type of breast cancer that's completely localized to the breast.
How is it different from invasive breast cancer?
Invasive breast cancer has developed the ability to spread elsewhere, so anyone with invasive breast cancer has a risk of developing metastases, such as cancer in the brain, in the liver, in the bone, etc. That's a much more serious threat to survival.
I think patients see the diagnosis as the equivalent of breast cancer diagnosis, and it terrifies them. So it can be quite difficult for women with DCIS to understand that their disease actually has an excellent survival rate. Over 98 percent of people with DCIS are alive 10 years after their diagnosis. They haven't died of breast cancer because breast cancer hasn't developed the ability to spread, whereas people with invasive breast cancer that has developed the ability to spread often need more treatment to try and decrease the risk of recurrence, or return, of breast cancer and of dying of breast cancer.
Why has the incidence of DCIS risen so sharply over the last decade?
It may just be becoming more common, but I think the main factor is screening mammography. Our screening mammography has improved and more women are taking advantage of it. Screening mammography is really good at finding calcifications, which are calcium deposits. Many of the cases of DCIS have calcifications that form in the ducts of the breast, which are picked up by a mammogram.
Why do we have to treat all cases of DCIS?
The main problem is that we know that if we leave DCIS alone and do not treat it all, many people will develop invasive breast cancer. They then have the same risks of dying of breast cancer as someone who develops invasive breast cancer.
Can you determine which cases of DCIS are likely to recur?
Some duct carcinoma in situs look more aggressive under the microscope than others, which we refer to as the grade. Also, there is a variant of DCIS that tends to be more aggressive called comedo-type DCIS. In these cases there are a lot of actively replicating cells, so under the microscope, you see a lot of cells that have died; the dead cells form something called a comedo.
A larger tumor and a tumor that is in multiple areas of the breast are both risk factors for recurrence. But even tumors that we think are low-risk for coming back can come back, too. So we can give what we think the likelihood of it coming back is, but we can never say that the likelihood is zero.
How is DCIS usually treated?
In general, we treat with lumpectomy followed by radiation. We know that radiation after lumpectomy decreases the rate of recurrence. Some of these people, whose tumors have hormone receptors and therefore may grow in response to hormones, get treated with hormone therapy, with tamoxifen or with other hormonal compounds. We're still acquiring evidence about the effect of hormonal therapy for DCIS.
If you have DCIS in multiple areas of your breast, you really can't save the breast and general mastectomy is necessary. Interestingly, mastectomy is more commonly necessary in DCIS than in your standard invasive breast cancer. So although it's a precancer, sometimes it requires a more aggressive surgical approach than invasive cancer.
Are there some people with DCIS who might not need radiation after lumpectomy?
I think that's one of the important questions that need to be answered, and that we need randomized studies to look at that specific question. If radiation doesn't really help people, then we're exposing them to problems associated with radiation for no reason. If we could be better than we are now in determining who is at high risk of having their DCIS come back, then we could just give those people the radiation and spare everyone else. That would be great, but we're not there yet.
Why wouldn't someone want the radiation?
Radiation is costly, and it does require a month of fairly intensive treatment. Radiation can lead to permanent deformities in the breast. Radiation can make it more difficult to screen the breast in the future because it can lead to changes within the breast such as scarring. It has also been associated with lung problems and heart problems in very small numbers of people.
What did your study suggest about the variability in treatment for DCIS?
Our study demonstrates that treatment is variable and changing. It seems that surgeons have adopted breast conservation for DCIS, and that the rate of mastectomy dramatically declined within a fairly short period of time, which is good. However, it is concerning that depending on where you're located geographically in the United States, your treatment for DCIS can be quite different.
Part of the issue is that the treatment is fairly controversial, and it does rely a lot on individual judgment. There may also be variation in women's preferences and in the provider practice and the institutional practice where the woman lives. If one provider or institution generally prefers to perform a certain type of operation or to deliver radiation after lumpectomy or not to deliver radiation, that influences the care the woman receives.
Did you see cases of undertreatment?
In the study, there was a wide variation in terms of delivery of radiation after lumpectomy, even for the type of DCIS that we know has a greater risk of recurring: the comedo-type DCIS. Up to a third of people with that type of DCIS did not receive radiation. So it does appear that some women are inappropriately not treated with radiation.
Did you see cases of over-treatment?
We see variation in terms of the rate of mastectomy between centers. Now some of that may relate to patient preference. There may be a greater preference for mastectomy in one area of the country than the other, though it's hard to know. But it seems unlikely that it explains all the variation. If women have a diffuse (spread out) tumor, then they do generally need to get a mastectomy. But there may well be women who don't have the diffuse tumor who receive mastectomy.
What is your advice then to a woman who has just been diagnosed?
Compared to invasive breast cancer, DCIS is relatively uncommon. Although it's increased in incidence, it still only about 15 percent of all breast cancers. So not every surgeon is going to be extremely familiar with the treatment of DCIS, even if they're relatively familiar with the treatment of breast cancer. We know that the outcome for most patients is great, but if we can avoid over-treating patients, that that would be the way to go. I think that if you're completely comfortable with the treatment plan, then that's fine. But if women are uncomfortable at all about their treatment plan, obtaining a second opinion is the way to go. But it's going to be a while before we get there. I think we really have to encourage research in this area to bring us from where we are today to where we should be.