One of the aims of gene expression profiling is to identify early breast cancer patients with a good prognosis who can avoid adjuvant chemotherapy.1
In our Institute, we obtained a 70-gene signature (MammaPrint)2 on 21 early breast cancer patients. All patients gave written informed consent approved by the Ethic Committee.
After the breast tumor was removed, a tumor sample was stored by pathologist and sent to Agendia for MammaPrint test.
Nine patients had a MammaPrint result which is not useful for clinical decision about adjuvant chemotherapy because 3 were ductal carcinoma in situ, 4 (22%) had quality of samples not sufficient to perform the MammaPrint assay and 2 had both oestrogen- and progesterone-receptors negative and then patients were candidates for chemotherapy regardless the MammaPrint results.
In the remaining 12 cases (67%) both clinical risk (defined by clinical-pathological parameters) and MammaPrint risk were considered for decision-making about adjuvant treatment. All cases were discussed in the Breast Disease Management Team with the presence of medical oncologists, surgeons and pathologists. Characteristics of the 12 patients are showed in Table 1.
In five (42%) cases (2, 4, 5, 6, 11) clinical risk was discordant with the risk estimated by MammaPrint. In these cases decision about chemotherapy was based on clinical-pathological factors and disagreed with MammaPrint risk. In fact, in our Institute we recommend chemotherapy in endocrine-responsive patients with node-positive (2 and 5) or T2 tumor or G3 or age ≤35 years. Conversely, we do not recommend usually chemotherapy in endocrine-responsive patients with age ≥70 years (4 and 6). Patient 11 had a lobular invasive carcinoma and, although she had a T2, we did not recommend chemotherapy because lobular invasive carcinoma appeared to be less responsive to chemotherapy.3
In two (17%) cases (8, 12) change in clinical decision was based on MammaPrint risk. Therefore, MammaPrint results led to a change in clinical decision in 2 of the 18 (11%) of total patient population undergoing MammaPrint.
Our results are concordant with a recent study with the aims of assess prospectively the feasibility of implementation of the 70-gene signature.4
Bueno-de-Mesquita et al. reported a similar rate of sampling failure or incorrect procedure (27% in Dutch study and 22% in our experience) and a similar rate of discordant cases between clinical-pathological characteristics and MammaPrint results (30 vs. 42%).
In this study, MammaPrint results led to a change in the treatment in 24% of patients compared with our data where change was seen in 11% of patients. Moreover, in Dutch study chemotherapy was added in 35 patients and withheld in 19 patients [net 16 (4%) patients had more chemotherapy]. In our experience MammaPrint led to add chemotherapy in two (11%) patients and to avoid chemotherapy in no patient.
In conclusion, our experience confirm that nearly 25% of patients are not assessable for MammaPrint for procedure failure. MammaPrint results lead to a change in clinical decision in less than 20% of total patient population. Finally, both our experience and Dutch study showed a potential increase instead of decrease in the use of chemotherapy.
Oncologists using MammaPrint results in clinical practice should be aware that the high rate of test failure may create unjustified expectations by patients and that such tool could be not useful to increase the percentage of patients who are spared chemotherapy.