(111)In-trastuzumab scintigraphy in HER2-positive metastatic breast cancer patients remains feasible during trastuzumab treatment

Human epidermal growth factor receptor (HER)2 imaging with radiolabeled trastuzumab might support HER2-targeted therapy. It is, however, frequently questioned whether HER2 imaging is also possible during trastuzumab treatment as the receptor might be saturated. We studied the effect of trastuzumab treatment on 111In-trastuzumab uptake. Patients received trastuzumab weekly and paclitaxel once every 3 weeks. 111In-trastuzumab was injected on day 1 of cycle 1 and day 15 of cycle 4. Whole-body planar scintigraphy was acquired at different time points postinjection. Tumor uptake and organ distribution between the first and repeated scan series were calculated via residence times. Twenty-five tumor lesions in 12 patients were visualized on both scintigraphy series. Tumor uptake decreased (19.6%; p  =  .03). The residence times of normal organs remained similar except for the cardiac blood pool (+ 16.3%; p  =  .014). Trastuzumab treatment decreases tumor 111In-trastuzumab uptake around 20%. HER2 imaging is feasible during trastuzumab treatment.

HER-2 and topoisomerase II as predictors of response to chemotherapy

HER2 overexpression or amplification has been shown to be associated with a poor prognostic effect in women with breast cancer. At least eight analyses based on randomized trials have examined the relationship between HER2 and the differential effect of anthracycline compared with non-anthracycline-containing regimens. Only three of these studies were sufficiently powered to show a significant interaction between HER2 and anthracycline- versus non-anthracycline-containing treatments, but because all of the study results tended to be in the same direction, it is not surprising that three recent meta-analyses of published data have suggested that anthracycline-containing regimens provide more benefit than non-anthracycline-containing regimens in women whose tumors are overexpressed or amplified (positive) for HER2. Since topoisomerase II is a known target of the anthracyclines, it has been postulated that this relationship is actually based on the proximity of HER2 to the topoisomerase II alpha gene (TOP2A) in the 17q chromosome. At least four recent studies have suggested that deletion and amplification of the TOP2A gene are associated with poor prognosis and are predictive of greater response to anthracycline-containing than to non-anthracycline-containing regimens. However, in at least one of those studies, HER2 positivity was as or more predictive. Although it has been suggested that HER2 positivity is predictive of better response to higher-dose anthracycline-containing regimens compared with standard anthracycline-containing regimens and to taxane- compared with non-taxane-containing regimens, these relationships have not been robust or consistent. Additional studies will be required to clarify these relationships.