When Rebecca Wolfgang had breast cancer, she had a mastectomy but not chemotherapy.
Mrs Wolfgang, of Hamilton South, was diagnosed with breast cancer in March last year.
"I was completely blindsided and couldn't believe it. I was a fairly healthy and active person," the 56-year-old said.
She had the mastectomy in April and 10 lymph nodes were removed from her armpit, with two found to be cancerous.
She was initially recommended to do chemotherapy, but her oncologist mentioned the Optima clinical trial, so she joined it.
Run by the Newcastle-based Breast Cancer Trials, the research aimed to safely reduce the use of unnecessary chemotherapy.
Chemotherapy is regularly offered to people with early-stage breast cancer that has spread to nearby lymph nodes, as it lowers the risk of the disease returning.
But there is concern that many people with hormone-receptor positive breast cancer, the most common form of the disease, receive little or no benefit from the powerful treatment.
However, they do experience its significant side effects.
The trial followed more than 4400 patients worldwide from 2017 to 2025, including 263 patients from Australia and New Zealand.
The findings showed people aged 40 and over with early-stage breast cancer can be treated safely with hormone-blocking therapy alone.
The patients who were selected to not have chemotherapy had tumours that scored low on a test that measures the activity of genes involved in breast cancer growth.
Associate Professor Belinda Kiely, chair of the Australian study, said the trial "addresses a long-standing challenge in breast cancer care: identifying who benefits from chemotherapy and who does not".
The findings showed that a substantial number of breast cancer patients could "safely avoid chemotherapy and its physical and emotional side effects without compromising their outcomes", she said.
The Optima trial used a genomic test called Prosigna to determine which patients could have treatment without chemotherapy.
The test, which measures the activity of genes involved in breast cancer growth, is performed on cancer tissue samples.
These samples are removed during surgery, but can also be done with a needle biopsy.
Mrs Wolfgang felt "very fortunate" that she did not need to have chemotherapy.
"There was less disruption to my life and I was able to move on," she said.
Her genomic test showed she had "a low risk of recurrence".
"So I could safely proceed to endocrine therapy without chemotherapy," she said.
"I'm on an oestrogen blocker tablet. That has some little side effects, but overall it hasn't impacted on my daily life.
"I feel well now."
As well as having no chemotherapy, Mrs Wolfgang was also able to avoid radiation.
"The radiation oncologist said there was no benefit from having radiation, considering my circumstances," she said.
Associate Professor Kiely said the Optima trial "successfully used tumour biology to guide treatment decisions, rather than relying solely on traditional clinical features".
"The results mark a significant step toward more personalised treatment," she said.
The research team found similar outcomes for pre- and post-menopausal women.
Pre-menopausal women all received hormone-blocking therapy that included ovarian function suppression.
The researchers believe this explains why chemotherapy did not appear to offer additional benefit in this group.
It is not yet known whether the findings apply to people under the age of 40.
