A test that looks at 70 different genes can identify women who have a very low risk of death from breast cancer after surgery, allowing them to avoid unnecessary treatment, according to a recent study.

In the study, published in JAMA Oncology, Laura Esserman, MD, of the University of California at San Francisco, and colleagues asked whether a “molecular signature” could be used to identify tumors that are indolent, or very slow-growing.

The researchers evaluated a breast cancer recurrence test called MammaPrint that screens for 70 genes that predict cancer progression and metastasis, or the spread of cancer beyond the breast.

The researchers looked at 20 years of data from a Swedish trial that compared adjuvant (follow-up) treatment with the estrogen-blocking drug tamoxifen or no medication after mastectomy or lumpectomy plus radiation in postmenopausal women with early-stage breast cancer.

A previous study showed that MammaPrint did a good job of classifying women as having a high or low risk of dying from breast cancer. Women with a low-risk genomic signature who did not receive chemotherapy had a survival rate similar to that of high-risk women who did undergo chemotherapy.

The current study established an even lower cutoff for ultralow risk. Based on MammaPrint scores, more than 650 women were classified as being at high risk (42 percent), low risk (58 percent) or ultralow risk (15 percent) for cancer progression after surgery and radiation.

Over 20 years, women with high-risk and low-risk tumors had a significantly greater risk of death from breast cancer than women with ultralow-risk tumors. Women in the ultralow group had a 20-year survival rate of 97 percent if they used tamoxifen, compared with 94 percent if they received no adjuvant therapy.

Researchers concluded that the ultralow-risk threshold can identify women whose long-term risk of dying from breast cancer is “exceedingly low,” meaning that these women could be spared overtreatment.

“We can now test small node-negative breast cancers, and if they are in the ultralow risk category, we can tell women that they are highly unlikely to die of their cancers and do not need aggressive treatment,” Esserman said in a press release from the Karolinska Institute in Stockholm.

A related study, also published in JAMA Oncology, compared outcomes for women who received combined mammography and MRI or ultrasonography screening after breast-conserving surgery, like a lumpectomy, and radiation therapy.

Breast-conserving surgery techniques are designed to preserve healthy breast tissue, however, compared with a full mastectomy, there is a greater risk that some cancerous cells will be left behind, so regular screening is necessary.

Nariya Cho, MD, of Seoul National University College of Medicine in Korea, and colleagues examined screening methods for cancer recurrence in women who were diagnosed with breast cancer at age 50 or younger.

Over three years, 754 women underwent annual MRI screenings, ultrasound and mammography. A total of 17 cancer recurrences were diagnosed, most of which were small (Stage 0 or 1).

Cancer detection rates were 8.2, 6.8 and 4.4 per 1,000 women, respectively, using MRI plus mammography, ultrasound plus mammography or mammography alone. That is, adding MRI detected 3.8 more cancers, and adding ultrasound detected 2.4 more cancers, than mammography alone.

“In younger women who had undergone breast conservation therapy, the addition of MRI screening or ultrasonography to mammography can be considered,” the researchers concluded.

To read the molecular test study abstract, click here.

To read the MRI and ultrasound study abstract, click here.