Optimal sequencing of anti-HER2 therapy throughout the continuum of HER2-positive breast cancer: evidence and clinical considerations

With the advent of the monoclonal antibody trastuzumab over 2 decades ago for breast cancer therapy, the outcome of patients with human epidermal growth factor receptor (HER) 2-positive disease has improved dramatically. Based on its substantial efficacy and good tolerability, trastuzumab has become the therapeutic gold standard for early as well as advanced breast cancer. Nevertheless, despite adjuvant trastuzumab, patients do experience recurrence and require further anti-HER2-targeted therapy. Next to the small molecule tyrosine kinase inhibitor lapatinib, which was the first approved therapy option after trastuzumab failure, several new anti-HER2 agents are currently already available for clinical use [i.e. pertuzumab, T-DM1 (trastuzumab emtansine)] or are still being evaluated (e.g. afatinib, neratinib). Recent evidence from neoadjuvant as well as metastatic therapy suggests that dual blockade may be superior to single-agent HER2 blockade. While the number of available or potential therapies has increased considerably, no additional predictive biomarkers beyond HER2 have been validated for the use of the different anti-HER2 therapies. Moreover, novel therapeutic concepts such as the antibody-drug conjugate T-DM1 warrant excellent determination methodology for HER2 and suggest re-evaluation of tumor biology upon first metastasis. The clinical challenge remains to optimally choose, utilize, and sequence anti-HER2 therapy in early as well as metastatic breast cancer. This article will provide evidence-based guidance for sequencing anti-HER2 therapy throughout the continuum of breast cancer therapy.

Loss of HER2 amplification following trastuzumab-based neoadjuvant systemic therapy and survival outcomes

PURPOSE

To evaluate HER2 status in residual tumor identified at the time of surgery in patients not achieving a pathologic complete response (pCR) and to determine the effect of alterations in HER2 status on recurrence-free survival (RFS).

EXPERIMENTAL DESIGN

Clinicopathologic data for patients with HER2-overexpressing breast cancer receiving neoadjuvant therapy with a taxane, anthracycline, and concomitant trastuzumab between 2004 and 2007 were reviewed. Surgical specimens for patients achieving less than a pCR were assessed to determine if there was enough residual tissue to evaluate posttreatment HER2 status. RFS was determined using the Kaplan-Meier method and compared by the log-rank statistic.

RESULTS

A pCR was achieved in 72 of the 142 (50.7%) patients. Residual tumor was sufficient to assess posttreatment HER2 status in 25 patients. Fluorescence in situ hybridization done on pretreatment specimens confirmed HER2 amplification before beginning therapy. Eight (32.0%) posttreatment tumors were found to be HER2-negative by fluorescence in situ hybridization. At a median follow-up of 37 months (range, 8-56 months), the RFS was significantly better for patients with tumors that retained HER2 amplification (87.5% versus 50%, P = 0.04).

CONCLUSION

High pCR rates are achieved in patients with HER2-positive breast cancer treated with neoadjuvant trastuzumab in combination with anthracyclines and taxanes. One third of patients with significant residual disease loses HER2 amplification, and this change is associated with poor RFS. Residual tumor identified at the time of surgery should be reassessed for HER2 status, and novel adjuvant therapy strategies need to be studied in this population.

Tumor marker phenotype concordance in second primary breast cancer, California, 1999-2004

Breast cancer is the most common cancer among women. It is estimated that 7% of women who have breast cancer will develop a subsequent second independent breast tumor within 10 years of the first. The status of estrogen (ER), progesterone (PR) and human growth hormone (HER2) receptors, individually and as phenotypic combinations, impacts the clinical course of breast cancer and may impact the course of subsequent primary tumors and patient survival. Our aims were to determine tumor marker phenotype concordance between first and second primary breast cancers (FPBC and SPBC), describe demographic and clinical characteristics, and examine first tumor treatments associated with phenotype concordance. A total of 76,209 cases of female invasive breast cancer were identified in the California Cancer Registry from 1999 to 2004. Of those, 1,407 women who had not undergone a prophylactic mastectomy, had information on the status of three tumor markers, and were diagnosed with an SPBC during the study period were selected. SPBCs were significantly smaller, diagnosed at a higher stage and were node positive. Patients whose FPBC was ER(+)/-/PR(+)/-/HER2- and triple negative (TN) (ER-/PR-/HER2-), often had concordant phenotypes for their SPBC. ER(+)/-/PR(+)/-/HER2+ and HER2-positive (ER-/PR-/HER2+) FPBCs, often had discordant phenotypes for their SPBC. ER(+)/-/PR(+)/-/HER2- SPBCs often lacked HER2 expression and were ER and/or PR positive. Tumor laterality and synchronicity significantly predicted concordance as did having a FPBC whose phenotypes were ER(+)/-/PR(+)/-/HER2+, HER2-positive and TN, while first primary tumor treatment with chemotherapy predicted discordance. The relationship between multiple primary breast cancer phenotype concordance and patient prognosis has yet to be determined. Our results indicate that SPBC surveillance strategies include consideration of FPBC phenotype. Although our results are provocative, they may have been influenced by current criteria used to determine tumor independence.