Who Can Delay Breast Cancer Treatment? A New Math Model Adds Clues

For some women with ductal carcinoma in situ (DCIS), which is also referred to as Stage 0 breast cancer, something called active surveillance—screening, sometimes in combination with hormone therapy— could be an option instead of surgery and radiation. Currently, it’s difficult for doctors to tell whether the abnormal cells in the milk ducts that characterize DCIS will progress to invasive cancer, or if they will remain harmless. But as TIME Magazine previously reported, there’s growing concern among women and their doctors that treating all DCIS cases like invasive cancer is costly and potentially harmful for some women.

The problem is a a dearth of clinical trials that assess outcomes in women with DCIS who choose treatment versus those who choose active surveillance. In that absence, researchers at Duke University have developed a mathematical model that helps determine whether certain women may benefit from active surveillance over immediate treatment, and who those women might be.

In the new study published in the Journal of the National Cancer Institute, the researchers used data from the Surveillance, Epidemiology and End Results (SEER) Program—a massive database at the National Cancer Institute—and created a risk-projection model for mortality from all causes in women with DCIS over a 10-year period. The researchers then used the model to assess how undergoing active surveillance compared to undergoing treatment as a risk for death.

Read more: Why Doctors Are Rethinking Breast-Cancer Treatment

“There is growing concern that we may be causing harm by using aggressive procedures for something that may never cause illness or death,” senior study author Dr. Shelley Hwang, chief of breast surgery at Duke Cancer Institute, said in a statement. “Our study was designed to provide some guidance for an alternative approach.”

Here is what the math model found:

—For women ages 69 to 71, the research team found that women who do active surveillance for DCIS were around six times less likely to die from breast cancer than another health problem.

—For women between the ages of 39 and 41, the researchers found that active surveillance resulted in a greater risk of death within 10 years compared to usual treatment.

—For women ages 54 to 56, the study authors found a higher risk of dying while undergoing active surveillance compared to usual treatment, but risk of death from breast cancer wasn’t very different from dying of other causes.

“In the end you have to talk to the patient and see if they are comfortable with that risk,” says lead study author Marc Ryser, a visiting scholar in the department of mathematics at Duke. “Based on all the information we have, this is our best estimate. But we don’t have all the information we need, and in the end, this is a model. I don’t think it will impact clinical practice, but it shows more research is needed to get high-quality data. It also helps to inform how to design clinical trials.”

Hwang is one physician helping to pioneer the move for a better understanding of DCIS, its treatment options and its outcomes. (You can read more about her work, and why doctors are rethinking breast cancer treatment in TIME’s recent cover story, here.)

Read more: Why Doctors Are Rethinking Breast-Cancer Treatment