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CHICAGO -- Patients with heavily pretreated metastatic breast cancer experienced a progression-free survival (PFS) benefit with sacituzumab govitecan-hziy (Trodelvy) versus physician's choice of chemotherapy, according to the TROPiCS-02 study.

In the phase III study, patients (n=543; 99% female) with HR+/HER2- metastatic breast cancer (MBC) who received prior endocrine therapy, CDK4/6 inhibitors, and two to four lines of chemotherapy, achieved a median PFS of 5.5 months with sacituzumab versus 4.0 months with treatment of physician's choice (TPC, P=0.0003), reported Hope Rugo, MD, of the University of California at San Francisco Helen Diller Family Comprehensive Cancer Center.

"Patients who received sacituzumab govitecan had a 34% reduction in the chance of death or worsening disease, with three times as many patients alive and without worsening disease at 12 months compared with patients who received chemotherapy," she said at a press conference at the American Society of Clinical Oncology (ASCO) annual meeting. At 12 months, 21% of the patients on sacituzumab govitecan were still alive and without disease progression versus 7% of TPC patients, Rugo noted.

"Sacituzumab govitecan demonstrated significant clinical benefit and manageable safety compared with standard chemotherapy in patients with heavily pretreated, endocrine-resistant hormone receptor-positive/HER2-negative advanced breast cancer, and should be considered a potential treatment option for these patients," she stated, adding that the safety profile of the agent in these patients was "manageable and consistent with previous studies; no new safety signals were identified."

Overall, 74% of patients getting the study drug had grade ≥3 treatment-emergent adverse events (AEs) versus 60% of TPC patients, most commonly neutropenia (51% vs 39%, respectively) and diarrhea (10% vs 1%). AEs leading to discontinuation occurred in 6% vs 4%, respectively. There was one treatment-related death in the sacituzumab arm and none in the TPC arm.

ASCO discussant Jane Lowe Meisel, MD, of the Winship Cancer Center at Emory University in Atlanta, pointed out that "as many as 96% of the women in the study had visceral metastases," and "many patients remained on the treatment they were assigned at the start of the trial, [so] there was a significant benefit to those patients on sacituzumab govitecan."

"I think this study will lead to sacituzumab govitecan becoming a new option for patients with heavily pretreated hormone-positive metastatic disease," she said. "This may be something that really changes the lives of these women for the better."

"Sacituzumab govitecan is an antibody to TROP2 found on the cell surface that delivers chemotherapy inside the cancer cell," explained press conference moderator Julie Gralow, MD, ASCO chief medical officer and executive vice president. The agent has in triple-negative metastatic breast cancer, based on results of the trial.

had 272 patients who got sacituzumab and 271 who received TPC. The median age was about 56, about 67% were white, and all had an ECOG performance status 0-1. As Meisel noted, the vast majority had visceral metastases at baseline.

The patients had been diagnosed with MBC for about 5 years pre-randomization with >60% receiving prior chemotherapy in the adjuvant/neoadjuvant setting, and 86% receiving prior endocrine therapy in the metastatic setting for ≥6 months. Also, well over half received prior CDK 4/6 inhibitors.

In a planned interim overall survival (OS) analysis, Rugo's group reported that the study drug versus TPC showed a numeric, but nonsignificant difference, in OS at 13.9 versus 12.3 months (HR 0.84, P=0.143). However, "results are not yet mature; and further follow-up for [OS] is ongoing," they stated.

"I think this [TROPiCS-02] will change practice," Gralow said. "I do think we have a new option now that has shown superiority over standard chemotherapy. Once the tumor has progressed on standard endocrine therapy, [patients'] only option has been chemotherapy, and now we have the option of an antibody-drug conjugate that is somewhat better in terms of PFS. It offers a new category of drugs for these tumors that have been proven to be very resistant," adding that once full study results are published in a peer-reviewed journal, "then we will move to incorporate this drug into the [breast cancer treatment] guidelines."

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