A novel combination has boosted responses in women with high-risk, HER2-negative breast cancer.
The new combo comprises the immune checkpoint inhibitor durvalumab (Imfinzi, AstraZeneca) and the poly(ADP-ribose) polymerase (PARP) inhibitor olaparib (Lynparza, AstraZeneca).
When this combo was added to standard neoadjuvant chemotherapy, it yielded a significantly higher pathologic complete response (pCR) rate at the time of surgery than was seen with chemotherapy alone.
The superior pCR rate was seen across all HER2-negative breast cancer subtypes, including HER2-negative, estrogen receptor–positive tumors (Mammaprint high risk), and in women with triple-negative breast cancer (TNBC), reported lead investigator Lajos Pusztai, MD, DPhil, from Yale Cancer Center in New Haven, Connecticut.
“These results provide further evidence for the clinical value of immunotherapy in early-stage breast cancer and suggest new avenues for how to exploit these drugs in hormone receptor [HR]–positive breast cancers,” said Pusztai.
He presented the results at the American Association for Cancer Research (AACR) virtual annual meeting, which took place online, owing to the COVID-19 pandemic.
Toxicities, including financial
“The benefits from immunotherapy are clearly emerging in early and metastatic triple-negative breast cancer, likely with PD-L1 expression. However, there’s much more uncertainty in patients with hormone-sensitive tumors whether there is benefit and who will benefit from immunotherapy,” commented Pamela N. Munster, MD, from the University of California, San Francisco, who was the invited discussant.
“The signal of a better pCR rate among patients in the ultra-high Mammaprint group may allow selection of patients with HR-positive disease who may benefit from immunotherapeutic agents and/or PARP inhibitors,” she said.
Munster noted that the approximately 10% higher rate of immune-related adverse events of grade 3 or greater that was seen with the combination appears similar to that seen in other studies, but anemia and fatigue appeared to be less frequent with durvalumab/olaparaib and paclitaxel in comparison with paclitaxel alone.
“In the absence of a clear delineation of the contribution of olaparib, some weight should be given to the financial burden of adding both durvalumab and olaparib to a preoperative regimen,” she said.
The additional cost of durvalumab is approximately $34,000, and adding olaparib boosts that by about $22,000 more, Munster said.
Ongoing platform trial
The new results come from one arm of the ongoing Investigation of Serial Studies to Predict Your Therapeutic Response Through Imaging and Molecular Analysis 2 (I-SPY-2) trial. This is an ongoing platform trial that is exploring the use of new drugs in combination with a standard neoadjuvant therapy backbone for the treatment of high-risk cancers.
In this trial, women with stage II or III breast cancer with tumors 2.5 cm or larger are assessed for one of eight biomarker subtypes according to HER2 status, HR status, and genetic risk factors, as determined on the basis of a 70-gene assay. The patients within each biomarker subtype are randomly assigned to receive standard therapy either with or without an investigational agent.
For each subtrial, a primary endpoint is an improvement in pCR in comparison with the standard of care.
Changes in tumor volume on MRI are used to predict whether patients will achieve a pCR. Those who are considered to have a high Bayesian predictive probability of success are eligible for moving on to phase 3 trials.
The I-SPY-2 trial was described in detail by principal investigator Laura J. Esserman, MD, MBA, from the Helen Diller Comprehensive Cancer Center at the University of California, San Francisco, in afrom the annual meeting of the American Society of Clinical Oncology.