CHICAGO – Trastuzumab deruxtecan (T-DXd) (Enhertu) already has proven efficacy against HER2-expressing metastatic breast, gastroesophageal, and lung cancers.
including malignancies of the cervix, endometrium, ovaries, bladder, and other sites.
The findings come from the ongoing DESTINY-PanTumor02 trial. Among 267 patients with solid tumors at various organ sites, the investigator-assessed objective response rate among all patients was 37.1%, and ranged from as high as 57.5% for patients with endometrial cancers to as low as 4% for patients with pancreatic cancer, reported Funda Meric-Bernstam, MD, from the University of Texas MD Anderson Cancer Center, Houston.
For patients with tumors that had HER2 immunohistochemistry (IHC) scores of 3+, the highest level of HER2 expression, the overall response rate was 61.3%..
The responses were also durable, with a median duration of 11.8 months among all patients and 22.1 months among patients with IHC 3+ scores.
“Our data to date showed that T-DXd had clinically meaningful activity across a variety of tumor types,” she said in a briefing held prior to her presentation of the data at the annual meeting of the American Society of Clinical Oncology.
“HER2 expression has been around a long time. We think about this all the time in breast cancer and drugs are approved there, but HER2 is expressed in other tumors as well, and that really represents an unmet need, because we have limited options in this situation” commented ASCO expert Bradley Alexander McGregor, MD, from the Dana-Farber Cancer Institute, Boston, an invited discussant at the briefing.
“Aside from pancreatic cancer we saw really, really encouraging results with no new safety signals, so while early I think this really exciting and represents a shift in how we think about cancer care,” he added.
After the presentation, invited discussant Kohei Shitara, MD, of National Cancer Center Hospital East, Kashiwa, Japan, said that he agrees with authors that T-DXd is a potential new treatment option for patients with HER2-expressing solid tumors, and that the evidence suggests the potential for further tumor-agnostic development of the agent.
He cautioned, however, that there is a lack of concordance between local and central assessment of HER2 IHC, and that quality assurance will be required to ensure that the HER2 status of solid tumors is accurately characterized.
At a press briefing, Dr. Meric-Bernstam was asked how she envisioned using T-DXd in therapy for various HER2-expressing tumors.
“I think the activity we’ve seen is quite compelling, and one hopes that eventually this will be a drug that’s accessible for patients that are HER2-expressing across tumor types. Clearly, the activity is very compelling in some of the diseases to think about doing studies for earlier lines,” she said.
“The data indicate that there is tumor-agnostic activity across the board,” she said, but noted that tumors with epithelial components such as ovarian and breast cancers appear to have the highest responses to T-DXd therapy.
Briefing moderator Julie R. Gralow, MD, chief medical officer and executive vice president of ASCO, asked Dr. McGregor whether, in the light of this new data, oncologists should test more patients for HER2 expression.
“We have some cancers where we know HER2 expression is there. I think the good thing about HER2 testing is that it’s an IHC test, so this is something that can be easily done in local pathology [labs],” he said. As more evidence mounts of potential benefit of T-DXd in HER2 expressing tumors, clinicians will need to consider more routine HER2 testing.