Gene test shows potential in radiotherapy decision-making for postmenopausal breast cancer
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A 21-gene recurrence score appeared useful for assessing locoregional recurrence risk among certain postmenopausal women with breast cancer who underwent whole-breast radiotherapy or mastectomy without postmastectomy radiotherapy, according to results of an analysis of the phase 3 SWOG S8814 study published in JAMA Oncology.
“As a field, breast radiotherapy is interested in personalizing radiation therapy beyond standard clinical factors. However, there are large ‘gray zones’ regarding recommendation for radiotherapy. A genomic-based assay that adds to the information we have would be a significant gain,” Wendy A. Woodward, MD, PhD, professor and chief of the clinical breast radiotherapy service in the department of radiation oncology at The University of Texas MD Anderson Cancer Center, told Healio.
“There was some evidence that the recurrence score is prognostic for local and regional recurrence events, but there is only one study in node-positive patients, which is not enough to change practice and drive its incorporation into clinical decision-making,” she added.
Results of the TAILORx trial showed the 21-gene expression test — known as Oncotype DX (Genomic Health) — could be used to identify women with node-negative, hormone-receptor positive, HER2-negative breast cancer who could forgo chemotherapy.
For the current analysis, Woodward and colleagues sought to determine if the 21-gene recurrence score could predict locoregional recurrence and aid in decision-making about radiotherapy.
They assessed the association between recurrence score and locoregional recurrence among 316 postmenopausal women (mean age, 60.4 years; range, 44-81) with ER/PR-positive, node-positive breast cancer included in the SWOG-8814 study. Women in the study had been randomly assigned to one of three treatment regimens: tamoxifen alone; cyclophosphamide, doxorubicin and fluorouracil chemotherapy followed by tamoxifen; or concurrent tamoxifen and cyclophosphamide, doxorubicin and fluorouracil.
Mean locoregional recurrence follow-up was 8.2 years. Median follow-up among women without locoregional recurrence was 8.7 years (interquartile range, 7-10.2).
Among 121 women with low recurrence scores, seven (5.8%) experienced locoregional recurrence events. Among 195 women with intermediate or high recurrence scores, 27 (13.8%) experienced locoregional recurrence events. Estimated 10-year cumulative incidence rates were 9.7% among women with low recurrence scores vs. 16.5% among women with intermediate or high recurrence scores (P = .02).
Among 252 women who underwent mastectomy without radiotherapy, researchers observed 10-year actuarial locoregional recurrence rates of 7.7% for those with low recurrence scores vs. 16.8% for those with intermediate or high recurrence scores (P = .03).
In a multivariable model that controlled for randomized treatment, number of positive nodes and surgical type, researchers found that a higher recurrence score appeared prognostic for locoregional recurrence (HR = 2.36; 95% CI, 1.02-5.45).
Further, results of a subset analysis of women who underwent mastectomy without radiotherapy and had one to three involved nodes showed women with low recurrence scores had a 1.5% rate for locoregional recurrence, whereas women with intermediate or high recurrence scores had an 11.1% rate for locoregional recurrence.
Limitations of the study included the retrospective extraction of data on use of radiotherapy, which may be underreported, and the inclusion of too few events to address the predictive role of recurrence score for radiotherapy or differentiate between local and regional recurrence.
“These data do not mean [recurrence score] should be used as the only important piece of information. Decision-making is still a nuanced discussion including all factors and existing randomized trial data, as well as patient preference,” Woodward told Healio. “We are now enrolling on TAILOR RT, a randomized phase 3 trial, to test omission of regional nodal irradiation in patients with a recurrence score of less than 18, with low-limited, node-positive disease.” – by Jennifer Southall
For more information:
Wendy A. Woodward, MD, PhD, can be reached at The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030; email: wwoodward@mdanderson.org.
Disclosures: Woodward reports personal fees from Genomic Health Inc. outside of the submitted work and a one-time advisory fee from Merck. Please see the study for all other authors’ relevant financial disclosures.
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