De-Escalation Trastuzumab/Pertuzumab ± Paclitaxel Yields Promising Responses in HER2+/HR– Early Breast Cancer

Patients with HER2-positive/hormone receptor–negative early breast cancer who experienced promising responses following de-escalated treatment with trastuzumab (Herceptin) plus pertuzumab (Perjeta) with our without weekly paclitaxel over 12 weeks, according to results from the phase 2 WSG-ADAPT-HER2+/HR– trial (NCT01817452) published in The Lancet Oncology.

The median follow-up was 59.9 months. In those who received paclitaxel vs those who didn’t, the 5-year invasive disease-free (DFS) survival rate was 98% (95% CI, 84%-100%) vs 87% (95% CI, 78%-93%; HR, 0.32; 95% CI, 0.07-1.49; P = .15). Moreover, the relapse-free survival (RFS) rate was 98% (95% CI, 84%-100%) vs 89% (95% CI, 79%-94%) in both respective arms (HR, 0.41; 95% CI, 0.09-1.91; P = .25) and locoregional RFS rate was 100% vs 95% (95% CI, 88%-98%; HR, 0.41; 95% CI, 0.05-3.75; P = .043), respectively.

Investigators also reported that DFS in the paclitaxel- and non-paclitaxel–treated patients, the distant DFS rate was 98% (95% CI, 84%-100%) vs 92% (95% CI, 83%-96%), respectively (HR, 0.35; 95% CI, 0.04-3.12; P = .36). The overall survival rate was 98% (95% CI, 84%-100%) vs 94% (95% CI, 86%-97%) in both respective groups (HR, 0.41; 95% CI, 0.05-3.63; P = .43).

A total of 134 patients were randomly assigned to either the trastuzumab plus pertuzumab group (n = 92) or the trastuzumab plus pertuzumab and paclitaxel group (n = 42). In both groups, 60% of tumors ranged from clinical stages 2 to 4, 43% were clinically node-positive, and 88% of tumors were grade 3 at baseline. Additionally, a majority of patients had a HER2 status of 3+ by local and central assessments.

Of those who did not receive paclitaxel, 34% experienced a pathologic complete response (pCR) vs 90% in those who did receive paclitaxel. Invasive DFS events were reported in in 1 patient with a pCR and 10 without a pCR in the non-paclitaxel group. In the group that did not receive paclitaxel, there was no difference in the 5-year invasive DFS rates between those with did and did not have a pCR. In the group that didn’t receive paclitaxel, 42% of patients experienced a pCR or minimal residual disease, with only 1 distant DFS event occurring.

Further chemotherapy was not administered in 57% of patients with a pCR. In all patients with a pCR, only 2 invasive DFS events were reported. For those who did have a pCR, the 5-year invasive DFS rate was 96% (95% CI, 77%-99%) in the continued therapy group vs 100% in those who did not have further treatment (HR, 1.84; 95% CI, 0.11-30.42; P = .67). For those in the non-paclitaxel group who did not receive further treatment, there were no invasive DFS events. Moreover, after 3 weeks on neoadjuvant treatment, 41% of patients had an early response in the non-paclitaxel group. Achievement of pCR was associated with improved DFS (HR, 0.14; 95% CI, 0.03-0.64; P = .011).

The post-hoc analysis indicated that the pCR rate was higher in the HER2 3+ tumors with an early response rate of 49% or a non-evaluable early response rate of 48% vs 12% of patients who did not have an early response. In the 13 patients with HER2 1+ or 2+ disease, there was no pCR reported (P = .0034). In total, 31 patients who were HER2-enriched, luminal, or unknown with intrinsic subtype of early breast cancer had a pCR compared with 7 patients who had a basal-like subtype.

In the non-paclitaxel group, of the 31 patients with non-sensitive tumors, the 5-year invasive DFS was 79% (95% CI, 59%-90%) vs 93% (95% CI, 81%-97%) in the 61 sensitive tumors (HR, 1.99; 95% CI, 0.61-6.55; P = .26).

Reference

Nitz U, Gluz O, Graeser M, et al. De-escalated neoadjuvant pertuzumab plus trastuzumab therapy with or without weekly paclitaxel in HER2-positive, hormone receptor-negative, early breast cancer (WSG-ADAPT-HER2+/HR-): survival outcomes from a multicentre, open-label, randomised, phase 2 trial. Lancet Oncol. 2022;23(5):625-635. doi:10.1016/S1470-2045(22)00159-0