CHICAGO (CBS) — Thousands of women are reacting to new evidence that could change their treatment for breast cancer.

A landmark study out of Chicago found most women in the early stages of the disease can safely skip chemotherapy.

Therese Dearth thought chemotherapy would be her only option, after she was diagnosed with an early stage of breast cancer March.  She says she received a call from her doctor stating otherwise.

“She told me that in this study they just completed, I am not even going to have to have chemo,” said Dearth.

The ten-year study, involving more than 10,000 women, used a 21 gene test on the tumor.

Patients received a s score between 1 and 100. Those with a score of 1-10 have been told since 2015, they do not need chemo.

The new finding is those with a score of 11-25 can now avoid chemo, as well.

A score of 25-100 means chemo is strongly recommended.

Therese Dearth’s score is at 16.

“It was just amazing!” said Dearth when she heard the news. “No other words for it. I was able to fall into this category and have such amazing news!”

The study’s findings were revealed at an annual meeting for the American Society of Clinical Oncology held at McCormick Place in Chicago.

Dr. Kathy Albain from Loyola Medicine is Therese’s oncologist and also a co-author of the study published in the New England Journal of Medicine.

Dr. Albain says it’s important to note the study involved women with the most common type of early stage breast cancer.

“Our days of uncertainty are over for maybe up to 70,000 women in the country right now,” stated Dr. Albain.

She says the women that are not undergoing chemotherapy must use endocrine therapy, which includes drugs that reduce the risk of the cancer returning.