Imagine that you go in for a regular mammogram and are told, happily, that you do not have breast cancer. But, your doctor says, you do have a significant risk factor for invasive cancer called ductal carcinoma in situ (DCIS), sometimes also called "stage zero" cancer. That means abnormal cells are lodged in one or more of the breast ducts—the "highways" connecting the milk-producing lobes to the nipples—but they haven't yet escaped to invade the other tissues in the breast. Will they ever do so? Maybe, maybe not.
It's not hard to see why a diagnosis of DCIS is confusing and frustrating. On one hand, you're told not to worry; you do not have invasive cancer and most likely never will (the 10-year survival rate is almost 100 percent, with treatment). On the other, you're told you need to have the cells surgically removed and, in some cases, may need radiation. So really, it's not so far off from what you'd go through if you did have cancer. And even though DCIS is almost always treated, scientists agree that not all cases would ever have turned dangerous. How did we get into this situation? And how do we get out of it?
According to a recent report by a National Institutes of Health state-of-the-science panel, mammography is largely responsible for the jump in DCIS cases. (Some 1 million women will be living with a DCIS diagnosis by 2020, the panel said.) Before the widespread use of mammography, most breast lesions were found when they were palpable tumors, says Carmen Allegra, chair of the NIH panel and chief of hematology and oncology at the University of Florida. Now, with the assumption that early detection is the best way to cure the disease, we go looking for breast cancer. And while that does find cancer at earlier stages, sometimes we find states that exist somewhere in between normal breast cells and cancerous ones.
In the case of DCIS, cells multiply rapidly and are different from normal ductal cells—they're different in size, shape, and architectural arrangement and more closely resemble invasive cancer, says Arnold Schwartz, professor of pathology at George Washington University Hospital in Washington and a member of the NIH panel. Not all DCIS is alike; there's a spectrum. The less closely the cells resemble their normal parent cells, the greater the potential danger seems to be, particularly in the presence of necrosis (dead cells) and in younger women (among other risk factors). All those factors suggest a potentially more-aggressive form of DCIS that may recur or become invasive cancer, says Schwartz.
Still, experts say, too little is known about the disease to be sure about which cases of DCIS will progress to invasive breast cancer and which will not. So with a few exceptions—such as small, low-grade tumors in elderly women with other health issues—standard practice is to treat the disease rather than monitor it over time to see if it progresses, says Lori Goldstein, director of the Breast Evaluation Center and coleader of the Women's Cancer Program at Fox Chase Cancer Center in Philadelphia. "If you could select which patients wouldn't progress, you could spare them treatment," she says. "We are probably overtreating some patients, but we don't have the tools" to identify them, she says. In that sense, DCIS has parallels to prostate cancer, which is also certainly overtreated—but in which patients, we don't know.
Right now, the treatment consists of surgery—either a lumpectomy or mastectomy, depending on how widely the cells appear in the ducts. If they're concentrated in one place, the usual treatment is a lumpectomy followed by radiation, which has been shown to cut the risk of recurrence in the same breast (but not the other breast) by half. Some women may have a mastectomy if the abnormal cells are found in many places; they don't need postoperative radiation. And some, particularly those who are young and may have a family history of breast cancer or a genetic mutation that puts them at high risk for the disease, even opt for a double mastectomy. "They may say, 'I'm not going to dance with the devil,' " says Marisa Weiss, a Philadelphia oncologist and founder of breastcancer.org. A study published in April in the Journal of Clinical Oncology found the rate of double mastectomy among DCIS patients rose from 4.1 percent in 1998 to 13.5 percent in 2005.