Distinct gene signatures, with the exception of estrogen receptor signaling and BRCAness, are associated with pathologic complete response and invasive disease-free survival, in patients with HER2-positive breast cancer who received trastuzumab and pertuzumab alone or in combination with paclitaxel.
Distinct gene signatures, with the exception of estrogen receptor (ER) signaling and BRCAness, are associated with pathologic complete response (pCR) and invasive disease-free survival (iDFS), in patients with HER2-positive breast cancer who received trastuzumab (Herceptin) and pertuzumab (Perjeta) alone or in combination with paclitaxel, according to data from a translational analysis of the WSG-ADAPT HER2+/HR– trial (NCT01817452).
Results, which were presented during the 2021 ESMO Breast Cancer Virtual Congress, indicated that the pathological complete response (pCR) rate with the addition of paclitaxel to trastuzumab and pertuzumab (arm B) was 78.6% vs 24.4% with trastuzumab and pertuzumab alone (arm A). RNA expression data were available for 117 patients.
For the combined analysis of arms A and B, investigators found that ER signaling and ERBB2 signatures were favorable for achieving a pCR, while PTEN signature was determined to be unfavorable. An analysis of arm A only, the neoadjuvant chemotherapy–free arm, indicated that ER signaling, ERBB2, and FOXA1 signatures were favorable for achieving pCR, while BRCAness signature was unfavorable.
Moreover, at a median follow-up of 60 months, a total of 13 iDFS events were observed; 11 were in arm A, while 2 were in arm B. No iDFS events occurred after achieving a pCR. Results from the combined analysis of the 2 arms indicated that immune-related signatures such as TIS, cytotoxic cells, cytotoxicity, macrophages, MHC2, PD-1, and IDO1, as well as ER signaling signature, were favorable for a better iDFS. For the arm A–only analysis, additional immune-related signatures—like APM, CD8+ T cells, IFNy, inflammatory cytokines, PD-L1, PD-L2, and regulatory T cells–were favorable for a better iDFS, but BRCAness signature was not.
Overall, 10 gene expression signatures were associated with pCR in arms A and B, with 18 of them in arm A alone. Moreover, 3 gene expression signatures were linked with pCR in both arms combined, with 4 of these in arm A alone. Eight gene expression signatures were found to be associated with iDFS in arms and B, with 16 in arm A alone.
“Activation of immune-related genes and pathways appears to be associated with improved iDFS in the entire cohort as well as the neoadjuvant chemotherapy–free arm A,” Monika Graeser, MD, of the University of Medical Center Hamburg, Germany, said in a presentation on the data. “Patients with upregulated immune-related gene signatures in their tumors could be candidates for de-escalation concepts in HER2-positive early breast cancer.”
HER2 is amplified and overexpressed in approximately 20% of all breast cancer cancers. Over the past 2 decades, the prognosis for patients with early-stage, HER2-positive breast cancer has significantly improved with the advent of HER2-targeted therapies. However, a high proportion of patients are still overtreated with toxic chemotherapy regimens, according to Graeser. Robust prognostic and predictive biomarkers are needed to establish new de-escalation or escalation strategies for this population.
In the phase 2 WSG-ADAPT HER2+/HR- de-escalation trial, investigators examined the added value of paclitaxel to dual blockade with 2 anti-HER2 agents: trastuzumab and pertuzumab. Patients needed to have HER2-positive, estrogen receptor–negative and progesterone receptor–negative disease, and an ECOG performance status of 0 or 1 or a Karnofsky performance score of 80% or higher. Their cancer could not have metastasized.
A total of 134 patients were randomized in a 5:2 fashion; of these patients, 92 received trastuzumab plus pertuzumab alone (arm A), while 42 received trastuzumab, pertuzumab, and paclitaxel (arm B). Trastuzumab was given every 3 weeks, starting at 8 mg/kg and de-escalated to 6 mg/kg; pertuzumab was also given every 3 weeks, starting at 840 mg down to 420 mg; and paclitaxel was given at a once-weekly dose of 80 mg/m2.
Treatment was given for 12 weeks, and surgery was performed within 3 weeks of completion. Adjuvant therapy was applied according to national guidelines, but chemotherapy could be omitted per investigator discretion.
The key end points of the trial included pCR, disease-free survival, overall survival, and safety. Investigators also conducted translational research, and data from these efforts were reported during the meeting. With this analysis, the goal was to identify the association of RNA expression signatures and stromal tumor-infiltrating lymphocytes (sTILs) measured at baseline and at 3 weeks with pCR and iDFS.
“Signatures were standardized, and hazard ratios were calculated for pCR and iDFS by logistic and Cox regression,” Graeser said. “In addition, we calculated Spearman correlations for gene expression signatures and sTIL at baseline and at 3 weeks. These calculations were performed combined for both arms [arms A and B] and for the neoadjuvant chemotherapy–free arm [arm A] separately.”
Investigators performed Spearman correlations within RNA expression signatures that were significantly associated with pCR and/or iDFS. Immune-related signatures formed a separate cluster, according to Graeser. ERBB2, BRCAness, and FOXA1 signatures were not correlated with immune-related signatures. Moreover, ER signaling and PTEN signature was not found to correlate with other signatures; they were independent markers, Graeser noted.
Correlations within RNA expression signatures and sTILs were also examined, at baseline (n = 119) and at week 3 (n = 76). No significant correlation was observed between sTILs—at baseline, week 3, or at the delta of the 2—and pCR and iDFS.
“However, we could see that baseline sTILs correlated with immune-related gene signatures,” Graeser said. “As such, we postulate that immune-related gene signatures can augment morphological data from sTILs regarding immune processes and outcome estimation.”
The investigators projected that multiplex immunohistochemistry could potentially play a key role in examining immune cells in the future.
The neoadjuvant chemotherapy–free concept of combining immunotherapy with dual HER2 blockade in patients with HER2-positive or HER2-enriched tumors is under examination in the phase 2 Keyriched-1 trial (NCT03988036), where investigators will also focus on examining immune activation.