NEW YORK (GenomeWeb News) â€" In a pair of papers appearing online today in the Lancet and Lancet Oncology, members of the Breast Cancer Intergroup of North America reported that some post-menopausal, estrogen receptor positive breast cancer patients benefit from the addition of chemotherapy to standard tamoxifen treatment.
And, the researchers found, the addition of chemotherapy was most beneficial for individuals scoring high on Genomic Health's Oncotype DX test, suggesting the recurrence assay may be helpful for guiding such treatment.
"Chemotherapy with [cyclophospamide, doxorubicin, and fluorouracil] plus tamoxifen given sequentially is more effective adjuvant therapy for post-menopausal patients with endocrine-responsive, node-positive breast cancer than is tamoxifen alone," lead author Kathy Albain, a hematology and oncology researcher at Loyola University, and her co-authors wrote in the Lancet paper. "However, it might be possible to identify some sub-groups that do not benefit from anthracycline-based chemotherapy despite positive nodes."
The studies stemmed from a 10-year, Southwest Oncology Group, phase III randomized trial in which researchers assessed 1,477 post-menopausal women with hormone receptor positive, node positive breast cancer.
In the Lancet study, the team assigned 550 women to a group receiving tamoxifen in conjunction with chemotherapy (cyclophospamide, doxorubicin, and fluorouracil). Meanwhile, 566 women got the chemotherapy treatment prior to starting tamoxifen treatment, while 361 women received tamoxifen alone.
After a median follow-up time of nearly nine years, the researchers found that women in the group receiving chemotherapy had better outcomes than those receiving tamoxifen alone.
In addition, the group that got chemotherapy before tamoxifen treatment tended to have slightly better disease-free and overall survival outcomes than the group getting chemotherapy and tamoxifen at the same time, though that result was not statistically significant.
Disease-free survival was around 60 percent in the group receiving chemotherapy before tamoxifen treatment, compared with 53 percent in the group receiving both treatments at once and 48 percent in the tamoxifen-alone group.
But the team also found differences within the groups. In their Lancet Oncology study, which is being presented today at the San Antonio Breast Cancer Symposium, the team reported that the Oncotype DX test appears to help identify women who are most likely to benefit from the addition of chemotherapy to their standard tamoxifen treatment.
The assay, which measures the expression of 21 genes in tumor samples to help predict chemotherapy outcomes and cancer recurrence, is typically used to classify women with node negative breast cancer. The new study suggests it may also be beneficial for guiding treatment in node positive women whose cancer has spread to the lymph nodes.
"With the right chemotherapy regimen, we can favorably impact survival," Albain said in a statement. "But it also is important to avoid the toxicity and medical costs of chemotherapy when it may not be needed."
For that study, collaborators at Genomic Health used the Oncotype DX RT-PCR assay to retrospectively assess banked samples from 367of the women who had participated in the initial Lancet study, comparing women in the chemotherapy-before-tamoxifen group with women in the tamoxifen-alone group.
Albain and her team found that women scoring high on the recurrence assay also got the most benefit from receiving chemotherapy prior to their tamoxifen treatment. In contrast, women with lower recurrence risk benefit less from the chemotherapy.
Consequently, those involved suggest the test could help to target chemotherapy to some and avoid the toxicity of unnecessary chemotherapy in others. Still, researchers noted, more studies are necessary to explore this further.
"This study, along with other studies involving different gene tests, suggests that certain biologic subtypes of breast cancer may inherently be either susceptible to chemotherapy or resistant to chemotherapy," Albain said in a statement. "Prospective studies with larger sample sizes are needed to determine who will optimally benefit from chemotherapy."
In a commentary accompanying the Lancet Oncology paper, medical oncologists Fabrice Andre and Suzette Delaloge, from the Gustave Roussy Institute of Oncology in France, discussed the new findings â€" as well as the future of such genomic testing for guiding breast cancer treatment.
The pair noted that the results that Albain and her colleagues reported "accord with previous findings that recurrence score is a prognostic variable for women treated with tamoxifen alone â€¦ However, their main finding, based on a clinically high-risk population, is that the 21-gene recurrence score could predict the efficacy of anthracyline-based chemotherapy."
Even so, Andre and Delaloge noted, although women in the high recurrence score group show the most obvious benefits of chemotherapy, more research is needed to determine whether the women with low recurrence scores also gain some benefit from the addition of this treatment.