Women with very early stage breast cancer who wait too long to receive radiation therapy after surgery have a significantly high risk of recurrence, according to a new study from Washington University School of Medicine in St. Louis.

The study was recently presented at the American Association for Cancer Research annual meeting this week.

Stage 0 breast cancer — also known as ductal carcinoma in situ (DCIS) — is detected based on the presence of abnormal cells in the milk ducts of the breast. In the U.S. in 2011, 57,650 women were diagnosed with noninvasive in situ carcinoma and of those, about 85 percent will be DCIS, according to the National Breast Cancer Coalition.

There is controversy about how to best treat DCIS since the abnormal cells don't always progress into invasive breast cancer. Dr. Ying Liu, the study's lead author, told HCB News it's because radiation therapy might over-treat low-risk DCIS.

Researchers at the university evaluated 5,916 women in the Missouri Cancer Registry who were diagnosed with DCIS from 1996 to 2011 and treated with lumpectomy. Out of those women, 17.8 percent received radiation therapy over eight weeks after surgery, 28.8 percent didn't receive any radiation therapy and 53.4 percent received radiation within the eight week time frame.

After a six-year follow-up 3.1 percent of the women experienced a recurrence of DCIS or an invasive tumor in the same breast. For those who received radiation within eight weeks, the rate of recurrence was 2.5 percent.

The risk of breast cancer recurrence was 26 percent higher for women who delayed radiation therapy and 35 percent higher for women who didn't initially receive radiation, after accounting for age, race, pathological factors, surgical margin status and hormone therapy.

Notably, the researchers found that African-American women, single women, women who received Medicaid, those whose DCIS tumors were larger and those who were diagnosed more recently were more likely to have a delay in radiation therapy.

The study did not find the reasons for delays among those groups, but Liu speculates that it's due to the quality and accessibility of health care providers and facilities.

More research involving a larger group of patients and a longer follow-up is needed to confirm the findings, said the researchers. The future studies should also address factors that may contribute to a delay in therapy, such as patient choice, health care providers, facilities and neighborhoods.

The researchers' ultimate goal is to provide "clear-cut" guidelines that will help more women reduce their rate of recurrence.

"My suggestion is that if radiation is recommended, it should be delivered as soon as possible," said Liu.

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