The EORTC 10041/BIG 03-04 MINDACT trial is feasible: results of the pilot phase

BACKGROUND

The MINDACT (Microarray In Node-negative and 1-3 node positive Disease may Avoid ChemoTherapy) trial investigates the clinical utility of the 70-gene profile (MammaPrint) for the selection of breast cancer patients for adjuvant chemotherapy (CT) together with standard clinicopathological criteria. We present the results of the pilot phase consisting of first 800 patients included.

METHODS

MINDACT has enrolled 6600 patients, classified into high or low risk by MammaPrint and clinicopathological risk through Adjuvant! Online. Patients with both clinical (C) and genomic (G) high risks are offered adjuvant CT; those with both C and G low risks do not receive CT; patients with discordant risk are randomised for the decision of adjuvant CT based on C or G risk. CT randomisation of anthracycline-based versus docetaxel/capecitabine and endocrine therapy randomisation between letrozole and tamoxifen→letrozole are offered.

RESULTS

During the pilot phase 46% of screened patients were enrolled. Main reasons for non-enrolment were node positivity before trial amendment, sample quality problems and failure to meet logistic settings. Among the 800 patients, 386 (48%) were C-low/G-low, 198 (24.8%) as C-high/G-high, 75 (9.4%) as C-low/G-high and 141 (17.6%) as C-high/G-low. In total 216 (27%) cases were discordant. The difference between patients with C-high (42%) and G-high risk (34%) is 8.25% (95% confidence interval (CI), 4.7-11.8%; P<.0001). Compliance with the treatment decision was high (>92%).

CONCLUSIONS

The logistically complex MINDACT trial is feasible in a multinational setting. The proportion of discordant patients, the potential reduction in CT by using the genomic signature and compliance to treatment assignment are in accordance with the trial hypotheses.

Characterizing the impact of 25 years of DCIS treatment

The significant increase in the detection and treatment of ductal carcinoma in situ (DCIS) since the introduction of screening mammography has not been accompanied by the anticipated reduction in invasive breast cancer (IBC) incidence. The prevalence of DCIS requires a reexamination of the population level effects of detecting and treating DCIS. To further our understanding of the possible impact of DCIS diagnosis and treatment on IBC incidence in the U.S., we simulated breast cancer incidence over 25 years under various assumptions regarding the baseline incidence of IBC and the progression of DCIS to IBC. The simulations demonstrate a tradeoff between the expected increased incidence of IBC absent any DCIS detection and treatment and the rate of progression of DCIS to IBC. Our analyses indicate that a high progression of DCIS to IBC implies a significant increase in incidence of IBC over what is observed had we not detected and treated DCIS. Conversely, if we assume that there would not have been a significant increase over and above the observed incidence evident in SEER, then our model indicates that the rate of DCIS progression to clinically significant IBC is low. Given the tradeoff illustrated by our model, we must reevaluate the assumption that DCIS is a short-term obligate precursor of invasive cancer and instead focus on further exploration of the true natural history of DCIS.