Real-world data comparison of time to next treatment for patients with HER2 positive metastatic breast cancer treated in the second line of therapy with fam-trastuzumab deruxtecan-nxki or ado-trastuzumab emtansine.

person Vikram C. Gorantla University of Pittsburgh Medical Center (UPMC), Pittsburgh, PA info_outline Vikram C. Gorantla, Anna Rui, Stephan B. Rosenfeld, Fred J. Kudrik, Anupama Vasudevan, Teena Sura, Mike Gart, Doug Kanovsky, Dawn Brenneman, Prateesh Varughese, Jeffrey A. Scott, Rushir J. Choksi, Robert B. Geller, Simon Blanc

Authors person Vikram C. Gorantla University of Pittsburgh Medical Center (UPMC), Pittsburgh, PA info_outline Vikram C. Gorantla, Anna Rui, Stephan B. Rosenfeld, Fred J. Kudrik, Anupama Vasudevan, Teena Sura, Mike Gart, Doug Kanovsky, Dawn Brenneman, Prateesh Varughese, Jeffrey A. Scott, Rushir J. Choksi, Robert B. Geller, Simon Blanc Organizations University of Pittsburgh Medical Center (UPMC), Pittsburgh, PA, Integra Connect PrecisionQ, West Palm Beach, FL, Highlands Oncology Group, Fayetteville, AR, South Carolina Oncology Associates, West Columbia, SC, Integra Connect, West Palm Beach, FL Abstract Disclosures Research Funding No funding sources reported Background: The Destiny-03 trial observed that a median progression-free survival was not reached in the patients (pts) treated with fam-trastuzumab deruxtecan-nxki (TDxd) and was 6.8 months in the pts treated with ado-trastuzumab emtansine (TDM1). We sought to evaluate the time to next treatment (TTNT), a surrogate for progression-free survival, between trastuzumab deruxtecan-nxki and TDM1 using real-world data to assess whether such pts see similar benefits beyond the clinical trial setting. Methods: We used the Integra Connect PrecisionQ real-world de-identified database of over 3 million cancer pts across 500 sites of care to identify 315 breast cancer pts for analysis. Each of the breast cancer pts was identified as HER2+ (IHC of 3+ or an ISH/FISH positive result) at the time of second line treatment initiation. The 315 pts were included so long as they started their second line treatment in the metastatic setting on or after 1/1/2022 through 12/31/2023. TTNT was measured from the treatment start to either the first of the initiation of a subsequent line of therapy or death. Descriptive analyses were used and TTNT was analyzed using a Kaplan-Meier analysis. Results: The median age was 62 (IQR 23-90) at time of treatment start. 100% of pts were female. 241 (76.5%) pts received TDxd with a median age of 62 at treatment start, while 74 (23.5%) pts received TDM1 with a median age of 62.5 at treatment start. The median TTNT was 19.0 months (95% confidence interval [CI], 14.1 to Not Reached [NR]) for pts who received TDxd compared to 9.2 months (95% CI, 6.7 to 13.0) for those who received TDM1 ( p <0.01). The median overall survival was not reached in either TDxd or TDM1 treated pts. The percentage of TDxd pts who were deceased was 13.3% compared to 14.9% for TDM1 pts. The probability of pts on therapy after 12 months was found to be 66% (95% CI, 58.7% to 73%) for those who received TDxd compared to 38.9% (95% CI, 25.2% to 52.4%) for those who received TDM1 ( p <0.01). Conclusions: HER2 positive metastatic breast cancer pts on second line treatment with TDxd experienced a statistically significant difference in TTNT compared those treated with TDM1. The real-world data shows that TDxd demonstrated superior clinical benefit to TDM1 in the treatment of HER2 positive second line pts. However, only 75% of pts received the recommended treatment option of TDxd, suggesting an opportunity to improve outcomes in HER2 positive pts.