CHICAGO – , according to a secondary analysis of data from the practice-changing TAILORx study.
Specifically, tumor size and histology-based risk stratification improves the prediction of disease-free survival and distant recurrence, and – for some patient groups – chemotherapy benefit,, reported at the annual meeting of the American Society of Clinical Oncology.
Combining these tools could help determine whether endocrine therapy (ET) alone or ET with adjuvant chemotherapy is the best treatment approach for a given patient, said Dr. Sparano, professor of medicine and obstetrics, gynecology, and women’s health at Albert Einstein College of Medicine, New York.
The phase 3study established that ET alone is noninferior to adjuvant chemotherapy (CT) plus ET in patients with early breast cancer and RS of 11-25, and that ET alone has some benefit over ET+CT in women aged 50 years and younger with RS of 16-25, he explained.
Those findings were presented at the 2018 ASCO annual meeting and subsequentlyin the New England Journal of Medicine.
The current analysis focused on the integration of clinical and genomic features for prognosis, and the results wereonline June 3 in a corresponding article in the New England Journal of Medicine.
“The totality of the data, including TAILORx and the prior prospective validation studies, indicate that assessment of genomic risk with the 21-gene recurrence score provides complementary prognostic information to pathologic features, and is also predictive of a large chemotherapy benefit if the recurrence score is greater than 25, or lack thereof if 25 or lower,” he said.
However, there is a three-way interaction between age, RS, and CT use, which results in an absolute CT benefit in women aged 50 or younger of about 2% for RS of 16-20, and about 7% for RS of 21-25, he added.
“Assessment of clinical risk using pathological features also provides prognostic information that doesn’t correlate well with the recurrence score, therefore it stands to reason that integration of clinical and genomic risk offers the potential for greater precision in prognosis and, ultimately, guiding the use of adjuvant therapy,” he said.
Clinical risk for this analysis was assessed using a binary clinical risk categorization employed in theand calibrated to greater than 92% 10-year breast cancer-specific survival for ET alone based on Adjuvant! version 8.0. Low-grade tumors up to 3 cm, intermediate-grade tumors up to 2 cm, and high-grade tumors up to 1 cm were categorized as low clinical risk (LCR), and all others not meeting these criteria were categorized as high clinical risk (HCR), he explained.
Of 9,427 patients included in the analysis, 70% had LCR and 30% had HCR.
“For distant recurrence, high clinical risk was associated with a 2.5- to 3-fold higher recurrence rate for those with a recurrence score of 11 or higher, and in a multivariate model for distant recurrence in the [group with a] recurrence score of 11-25, high clinical risk was independently associated with a 2.4-fold higher recurrence risk,” he said. “Continuous recurrence score also provided significant prognostic information, with each 1-unit increase associated with an 8% higher distant recurrence risk.”
For the overall population, clinical risk added significant prognostic information to the RS for both distant recurrence and disease-free survival, and stratification by age showed that among women over age 50 years, the hazard ratios for distant recurrence ranged from 2.20 to 2.36, and did not substantially vary by age or RS, he said.
However, for the overall population, adding clinical risk to the RS did not improve prediction of chemotherapy benefit.
“This was also true for the two-thirds of women who were over 50 years of age. For the remaining women 50 or younger, there was a trend favoring chemo, irrespective of clinical risk, though not significant – a finding consistent with the treatment interaction previously described,” he said.
Finally, the absolute differences in 9-year distant recurrence rates by clinical risk stratified by age, RS, and CT use showed an absolute 4%-6% higher distant recurrence risk for HCR vs. LCR among those over age 50 with RS of 0-25 irrespective of CT use, and a 13% difference for those with RS of 26-100 who were treated with CT.
“For those 50 or younger, clinical risk had no impact on recurrence if the RS was 0-10. For RS of 11-25, the difference was about 9% with endocrine therapy alone, and 2% with chemo plus ET, reflecting absolute chemo benefit in younger women who had high clinical risk,” he said, adding that for those with RS of 26-100, there was a 9% higher absolute recurrence rate in the HCR vs. LCR population.
“We therefore further evaluated absolute differences in distance recurrence rates associated with chemotherapy use in women 50 and younger with RS of 16-25, further stratified by RS and clinical risk,” he said, noting that when not stratified by clinical risk, as reported in the primary analysis, the absolute CT benefit was 1.6% for RS of 16-20, and 6.5% for RS of 21-25.
When stratified by clinical risk, the absolute CT benefit ranged from 6% to 9% in those with RS of 21-25, irrespective of clinical risk, and in those with RS of 16-20 and HCR.
“This accounted for 51% of patients with RS of 16-25,” he said. “However, there was no demonstrable chemo benefit for those with LCR and RS of 16-20, who accounted for the remaining 49%.”
Additional analysis looking at age at diagnosis and CT benefit showed a benefit in premenopausal women aged 46-50 years (but not postmenopausal women), a trend toward benefit in those aged 41-45 years, and no benefit in those aged 40 years and younger, who are less likely to develop premature menopause as a consequence of cytotoxic CT.
“In addition, we saw no consistent effect favoring chemotherapy in older women. Taken together, these findings suggest the chemo benefit observed for the RS 16-25 group may, in fact, be due to a castration effect associated with cytotoxic therapy rather than an effect in eradicating micrometastatic disease,” Dr. Sparano said.
Applying this framework to the TAILORx study population categorized 68% of those aged 50 years and younger into a low integrated risk group with less than 5% risk of distant recurrence. This included all patients with RS of 0-10 irrespective of clinical risk (14% of the patient population; distant recurrence rate 1.8% or less), and all with RS of 11-25 and LCR (54% of the patient population, 4.7% distant recurrence rate).
In contrast, 25% fell into the high integrated risk group (greater than 10% distant recurrence risk), including those with RS of 11-25 and HCR (17% of the patient population; distant recurrence rate 12.3%), and RS of 26-100 and HCR (8% of the patient population; distant recurrence rate 15.2%).
“This framework encompasses 93% of all TAILORx subjects, with the remaining 7% having a distant recurrence risk of between 5% and 10%,” he said.
Overall, the primary results of TAILORx remain unchanged based on this secondary analysis as the addition of clinical risk did not predict CT benefit in the RS 11-25 group, he noted.
“However, for women 50 and under and RS 16-25, integrated risk distinguished 50% who derived no chemo benefit from the 50% who derived an absolute benefit of approximately 6%-9% – a level that is higher than an unselected population,” he said, reiterating that the absolute CT benefit was greater in premenopausal women aged 45-50 with RS 16-25, suggesting that the absolute CR benefit seen in younger women in TAILORx may be due to an endocrine effect.
“Integrated risk clearly provides greater prognostic precision and may have clinical utility; the prognostic precision afforded by the integrated risk model is superior to that by the use of clinical or genomic features alone, and in addition, the genomic assay also provides predictive information for chemo benefit that is not captured by clinical features alone,” he concluded.
As an example of the potential clinical utility of this integrated approach for guiding treatment in women aged 50 years or younger, he presented “a highly stratified integrated risk assessment model” separating TAILORx patients into low integrated risk (58% of the study population) and high integrated risk (31% of the study population).
In the low integrated risk patients with RS of 0-10 and any clinical risk level, or with RS of 11-25 and LCR, tamoxifen alone appears adequate, he said.
In those with high integrated risk and RS of 16-25 with HCR, ovarian function suppression plus an aromatase inhibitor (OFS/AI) could be considered as an alternative to chemo, and in those with high integrated risk, RS of 26-100, and HCR who have not developed chemotherapy-induced menopause, ovarian function suppression and an AI could be added to chemotherapy.
“Indeed, data from theand trials indicate that patients with a high RS risk experienced an absolute improvement of up to 10%-15% in 5-year breast cancer–free interval with an OFS/AI, compared with tamoxifen, whereas improvement was minimal in those at lowest risk, supporting the strategy of using integrated clinical and genomic risk to select for ovarian function suppression plus an AI,” he said.
During a discussion of the findings and how they might impact practice,, an oncology professor and codirector of the Breast Cancer Program at Johns Hopkins University, Baltimore, noted that in her practice she will “carefully select women for whom genomic assay [use] is appropriate.