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TAILORx High-Risk Group Analysis Adds to Oncotype DX Chemo-Prediction Data

NEW YORK – In secondary analysis of data from the TAILORx trial, researchers have added new confirming evidence that patients with high risk scores from Genomic Health's Oncotype DX appear to benefit significantly from added chemotherapy.

Investigators led by the trial's PI Joseph Sparano shared their findings in JAMA Oncology today and also presented the analysis at the European Society for Medical Oncology 2019 Congress.

The TAILORx trial did not randomize women with high risk scores (26-100). They all received care according to their physician's choice, which largely included chemotherapy. But using data from previous randomized cohorts, study authors were able to estimate the impact chemotherapy may have had on the group, based on their rate of distant recurrence (93 percent) compared to what would be expected had they not received this added treatment.

The study also offered the chance to analyze the outcomes of different chemotherapy regimens undertaken by high-risk women in the trial, which did differ, in some cases significantly.

Genomic Health highlighted the data as further support for the ability of the test to predict which patients benefit from chemo and which do not. The main readout from the trial, released last June, prospectively established the test's ability — in the randomized, intermediate risk score group — to provide a clear cutoff point below which women can be expected to gain no benefit from chemotherapy.

Chemo benefit for those with high Oncotype DX risk scores had already been established in earlier studies, namely, the analysis of the test in the National Surgical Adjuvant Breast and Bowel Project B20 trial cohort. In B20, patients with hormone receptor-positive, node-negative breast cancer were randomized to tamoxifen or chemotherapy plus tamoxifen.

Genomic Health retrospectively analyzed tissue samples from 651 patients in the trial and compared results of its test to recorded patient outcomes — concluding that 10-year distant recurrence-free survival rates were 62 percent with tamoxifen alone, and 88 percent with chemotherapy plus tamoxifen, a statistically significant association, suggesting that high RS was not only prognostic for a high distant recurrence rate, but also predictive of chemotherapy benefit.

This data was enough for guidelines bodies to recommend the use of Oncotype DX to predict which breast cancer patients need chemotherapy, and for the company to promote its assay as chemo-predictive although questions about the risk score cutoff point lingered until the TAILORx publication last year.

In their new study of the TAILORx cohort, Sparano and other investigators examined outcomes for a much larger group of high risk score women than the B20 analysis, looking at outcomes among 1,389 women in the trial who had risk scores of at least 26 and who were treated largely with standard of care taxane and/or anthracycline-containing adjuvant chemotherapy regimens.

According to the authors, the proportion of these women who were distant recurrence-free at five years was about 93 percent, an outcome much better than expected with endocrine therapy alone in this population, based on the earlier findings in B20 and other trials.

Using the B20 results, for example, study authors calculated that the only about 79 percent of high-RS women in the trial would have been distant recurrence free at five years, and 65 percent at nine years.

"This new analysis provides the largest dataset on outcomes in patients with high [RS] results and confirms the importance of using the test to identify the patients who will receive a significant benefit from adding adjuvant chemotherapy," Sparano said in a statement.

The study also allowed the researchers to explore chemotherapy response more granularly, within this larger population with more heterogeneous treatments. According to the authors, likelihood of making it 5 years without recurrence of breast cancer ranged from 92 percent to 95 percent for all chemotherapy regimens, save cyclophosphamide/methotrexate/5-fluorouracil, which was associated with a significantly lower rate of about 88 percent. Interestingly women who received no chemo also had similarly low rates (almost 93 percent) of 5-year cancer distant recurrence.

Five-year rates of invasive disease-free survival, meanwhile, ranged more widely — from 84 percent to 92 percent — across chemo regimens, and were clearly lower, about 80 percent, for women who got no chemo.

Oncotype DX is not currently designed or marketed to aid in the choice of one chemotherapy regimen over another, but the company had in the past discussed trying to adapt the assay in that vein.