NeoAdj. Therapy Comparing Sacituzumab Govitecan (SG) vs. SG+Pembrolizumab in Low-risk, Triple-neg. EBC (ADAPT-TN-III)

About 15% of breast cancers lack both, expression of ER and PR receptors, and amplification/over-expression of HER2 receptors, and are thus described as triple negative breast cancer (TNBC). TNBC is known for poor prognosis, aggressive patterns of disease, and significant molecular heterogeneity. (Neo)adjuvant chemotherapy (NACT) is standard of care in all node-positive and in node-negative patients with a tumour size \>5 mm according to current National Comprehensive Cancer Network (NCCN) guidelines. However, TNBC patients with lower stage disease do clearly have a better prognosis compared to more advanced stages. Patients with stage I-II node-negative disease have 3-5 year iDFS rates of 80-90% (with majority of relapses within the first three years) as shown in several trials. Our own results from the PlanB- and ADAPT-trials, and pooled analysis with SUCCESS C-trials show 3-year iDFS of 86-90% in node-negative TNBC with a tumour size \< 3 cm. Although survival results appear much better in the lower vs. higher stages, there is a high clinical need in this most common group of TNBC patients in Western Europe and USA.

In the neoadjuvant setting, it has been shown that the prognosis of patients with TNBC is strongly dependent on their response to NACT: Patients achieving pathological complete response (pCR), or a near pCR (an excellent response after NACT (residual cancer burden (RCB) score 0-1), in some studies do have an excellent prognosis that is not significantly different from that observed in other breast cancer subtypes. However, patients with a less responsive disease (i.e., with RCB Score 2-3) suffer from a significantly worse prognosis compared to non-TNBC.

Chemotherapy in TNBC The optimal chemotherapy regimen for patients with TNBC remains to be identified. Standard anthracycline-taxane (A/T)-based NACT combinations render pCR rates between 25-50%. However, the survival impact of anthracyclines remains controversial due to conflicting results of different randomized trials. Adding carboplatin (carbo) to A/T-containing poly-NACT or use of dose-intensified poly-NACT significantly increases pCR-rates up to 49-60% in mostly stage II-III disease with conflicting survival results and higher toxicity. Hence, use of pragmatic taxane-carboplatin anthracycline-free combinations appears as an effective treatment option in TNBC instead of further treatment escalation. This probably is independent of the germline BRCA (gBRCA) status, due to its general chemo-predictive effect. Unfortunately, no prospective phase-III-data are available so far. However, indirect comparison between trials renders similar pCR rates in taxane-carboplatin based vs. A/T+/-carbo-based regimens in early TNBC.

In the ADAPT-TN neoadjuvant trial, the taxane-carbo arm (12-week nab-paclitaxel (nab-pac)+carbo) was well tolerable (only 10% SAE-rate), highly effective (pCR, ypT0/is/ypN0, of 46%) and superior to the gemcitabine (gem)-arm (nab-pac+gem, pCR of 29%). In this study, omission of further chemotherapy was allowed in patients with pCR after 12 weeks of therapy and was not associated with decreased survival after 3 years \[5\] and longer follow up.