Among women with small, node-negative breast cancers, those with tumors that are HER2-positive have a higher risk of cancer recurrence. This suggests that consideration of HER2-targeted therapy such as Herceptin® (trastuzumab) may be important, even for women with small tumors. These results were published in the Journal of Clinical Oncology.
Twenty to 25 percent of breast cancers overexpress (make too much of) a protein known as HER2. Overexpression of this protein leads to increased growth of cancer cells and a worse breast cancer prognosis. Fortunately, the development of drugs that specifically target HER2-positive cells has improved prognosis for women with HER2-positive breast cancer.
A question that remains uncertain is the need for HER2-targeted therapy among women with small (1 centimeter or less) HER2-positive breast cancers. To explore the behavior of these small cancers, researchers in the United States and Italy conducted studies of women with HER2-positive and HER2-negative breast cancers.
The U.S. study evaluated the records of 965 women with small cancers that had not been treated with HER2-targeted therapy or chemotherapy. By the end of five years, 6% of women with HER2-negative breast cancer had a recurrence compared with 23% of women with HER2-positive breast cancer.
The Italian study evaluated 150 women with small, HER2-positive breast cancers and 229 women with small, HER2-negative breast cancers. None of the women had been treated with HER2-targeted therapy. Overall, women with HER2-positive breast cancers were more than twice as likely to develop a cancer recurrence.
The results of these two studies suggest that even small HER2-positive breast cancers have an increased risk of recurrence. Consideration of adjuvant treatment with HER2-targeted therapy may be important for most women with HER2-positive breast cancer regardless of the size of the cancer. It should be noted, however, that these studies did not directly assess the effectiveness of HER2-targeted therapy in women with small cancers.
An accompanying editorial cautions that HER2-targeted therapy still may not be warranted in women with very small cancers (T1a or microinvasive; 0.5 cm or smaller). The authors of the editorial state: “We suggest that consideration of trastuzumab plus chemotherapy generally be limited to patients with T1b or larger cancers, and we believe that among patients with small T1a or microinvasive cancers, it is less likely that the tradeoffs of risk and benefit warrant chemotherapy plus trastuzumab.”
 Gonzalez AM, Litton JK, Broglio KR et al. High risk of recurrence for patients with breast cancer who have human epidermal growth factor receptor 2-positive, node-negative tumors 1 cm or smaller. Journal of Clinical Oncology [early online publication]. November 2, 2009.
 Curigliano G, Viale G, Bagnardi V et al. Clinical relevance of HER2 overexpression/amplification in patients with small tumor size and node-negative breast cancer. Journal of Clinical Oncology [early online publication]. November 2, 2009.
 Burstein HJ, Winer EP. Refining therapy for human epidermal growth factor receptor 2-positive breast cancer: T stands for trastuzumab, tumor size, and treatment strategy. Journal of Clinical Oncology [early online publication]. November 2, 2009.
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