Financial toxicity in patients with metastatic breast cancer on trastuzumab deruxtecan (T-DXd).
Authors: Lapen Kaitlyn , Dee Edward Christopher Christopher , Thom Bridgette , Aviki Emeline Mariam , Chino Fumiko 
Published: June 2024

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Background: T-DXd is a targeted therapy shown to improve outcomes in patients with metastatic breast cancer (MBC) who progressed on prior HER2 targeted therapies, or in the “HER2-low” population as presented at ASCO 2022. It is given every 3 weeks and costs about $9,500 per cycle. Little is known about treatment courses for patients on T-DXd and the potential financial toxicity (FT) of treatment including unmet essential needs. Methods: Retrospective review identified all patients with MBC treated with T-DXd from 6/2022 to 8/2023 at a comprehensive cancer center. Cross-sectional patient surveys assessed FT (via validated COST tool), ability to meet essential needs, payment concerns, and quality of life (QOL). Logistic regression assessed factors associated with unmet needs. A cohort of patients with MBC who did NOT receive T-DXd but completed a FT survey during the study period were identified for comparison. Results: 429 patients with MBC received T-DXd during the study period with a median of 7 cycles (IQR 3-12), and median length on treatment of 4 months (IQR 1.5-8). 164 (38% of the full cohort) completed a FT assessment after receiving at least one T-DXd cycle. Mean age at assessment was 56.9 years (SD 10.9); 72% identified as non-Hispanic White (NHW). Mean FT score was 19.2 (SD 10.8) (scale 0-44, lower scores indicate worse FT). 68% had COST <26 diagnostic of FT. Mean QOL score was 6.3 [(SD 2.0) 0 “as bad as it can be” - 10 “as good as it can be]. QOL was correlated with FT score (r=0.48, p<0.001). 21% of those who complete FT assessment had used at least some of their savings to pay for cancer treatment (5% had used all); 5% did not have savings to begin with. 23% took on new loans or borrowed money. Unmet essential needs were identified for: housing (15%), transportation (15%), food (11%), and repairs to home (10%). 11% reported they did not have enough monthly income for medications. On adjusted analysis including age, race/ethnicity, and FT status, those aged 46-65 years (OR 3.94, 95% CI 1.34-11.53, p=0.012), non-NHW (OR 4.54, 95% CI 1.86-11.08, p=0.001), and those with FT (OR 11.52, 95% CI 3.90-34.07, p<0.001) were more likely to have an unmet essential need. Of those who screened positive for FT, 50% accepted referral for financial assistance. 440 patients with MBC completed a FT assessment but did NOT receive T-DXd. There was no difference in FT (COST: 19.9 vs. 19.2, p=0.492) or unmet needs (36% vs. 37%, p=0.850). Conclusions: After ASCO 2022, hundreds of patients with MBC received T-DXd at a large cancer center; however, most did not stay on treatment for long. Patients with MBC had significant FT, although this is not unique to treatment with T-DXd. This underscores the need to study and intervene upon FT across all MBC populations given negative influence on QOL and unmet essential needs identified. Additionally, improving the referral process is essential, as only half of those with identified needs accepted referral for assistance.