NEW YORK (Reuters Health) - Adjuvant trastuzumab improves survival in women with breast cancer positive for human epidermal growth factor receptor 2 (HER2) whose tumors are no larger than 2 cm, according to a meta-analysis.
"Overall, our efficacy analysis conclusively showed that patients with HER2-positive tumors 2 cm (or smaller) treated in the randomized trastuzumab trials derived a significant disease-free survival (DFS) and overall survival (OS) benefit from adjuvant trastuzumab treatment," Dr. Ciara C. O'Sullivan, from the National Cancer Institute, Bethesda, Maryland, told Reuters Health by email. "However, given the fact that the majority of patients in our meta-analysis had T1c disease and/or node-positive disease, these results are not applicable to patients with T1a/T1b node-negative patients."
How best to treat women with small HER2-positive tumors remains controversial, as they are underrepresented in randomized clinical trials.
Dr. O'Sullivan's team conducted an individual patient data meta-analysis to compare the efficacy of adjuvant trastuzumab versus no trastuzumab for women with HER2-positive breast cancer and tumors 2 cm or smaller. They included 4220 women from five randomized clinical trials in their meta-analysis.
Overall, 2588 patients received adjuvant trastuzumab. Of the 2263 who had hormone receptor (HR)-positive disease, 94.1% received endocrine therapy. Only 3.3% of the 1957 women with HR-negative disease received endocrine therapy. Most patients (80% of HR-positive and 82% of HR-negative) had T1c disease.
At eight years, the cumulative incidence of a DFS event was significantly lower for women assigned to receive trastuzumab than for women who did not receive trastuzumab (17.3% vs 24.3%, P<0 .001="" 22="" according="" clinical="" journal="" june="" of="" oncology="" online="" p="" report.="" the="" to="">
Overall survival was also significantly higher at eight years in the trastuzumab group than in the no trastuzumab group (92.2% vs 88.4%, P=0.005).
In subgroup analysis, women with HR-positive disease had significantly greater DFS with trastuzumab (87.3%) than without it (80.6%). Overall survival also improved with trastuzumab, but the difference fell short of statistical significance.
Although women with HR-negative disease fared worse, the benefits of trastuzumab on DFS (a 9.4 percentage point gain) and OS (an 8.8 percentage point gain) were larger and statistically significant (P<0 .001="" p="">
"While the proportional benefit of trastuzumab was similar in patients with HR-positive disease compared with those with HR-negative disease, the patterns of incidence and relapse appeared to differ over the follow-up period," Dr. O'Sullivan said. "This suggests that HR-negative/HER2-positive disease is different biologically from HR-positive/HER2-positive disease. Therefore, perhaps these two subgroups should be considered separately in future clinical trials."
"Unfortunately, the question regarding the efficacy of adjuvant trastuzumab use in patients with T1a or T1b node-negative tumors remains largely unanswered and is controversial," Dr. O'Sullivan said.
"As prospective randomized trials to answer this question are unlikely to ever be conducted for a number of reasons, physicians should adopt an individualized approach to the management of these patients. Generally, patients with tumors 0.5 cm (or larger) with adverse clinicopathologic features such as high-grade disease, estrogen receptor-negative disease, and lymphovascular invasion should be considered for treatment with adjuvant chemotherapy and trastuzumab, medical comorbidities permitting," she added.
Six coauthors reported relationships with pharmaceutical companies, including for some, Roche-Genentech, marketer of trastuzumab (Herceptin).
SOURCE: http://bit.ly/1FxbsUE
J Clin Oncol 2015.
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