Real-world treatment patterns and outcomes in metastatic squamous cell carcinoma of the anal canal (SCAC): A retrospective electronic health record study.

5 Background: SCAC is a rare malignancy with rising incidence and mortality; in the metastatic setting, disease burden, treatment sequencing, and survival remain poorly characterized in real-world practice. Methods: This retrospective study analyzed structured data from the iKnowMed electronic health record system within a large U.S. community oncology network. Adults diagnosed with SCAC between January 1, 2019, and December 31, 2023, who had stage IV disease at diagnosis or who developed metastatic disease after an initial stage I–II diagnosis and received first-line (1L) systemic therapy were included. Pts enrolled in interventional trials or with non-SCAC primary tumors were excluded. Outcomes assessed included patient (pt) characteristics, treatment regimens across 1L, second- (2L), and third-line (3L) settings, and time-to-event measures: overall survival (OS), real-world time to treatment discontinuation (rwTTD), and real-world time to next treatment (rwTTNT). Pt characteristics and treatment regimens were evaluated using descriptive statistics; time-to-event measures were analyzed with the Kaplan–Meier method. Results: A total of 261 pts met the inclusion criteria. The median age was 64 years (interquartile range: 56–71); 70.9% were female, and 85.6% were White among pts with documented race data. Most pts with documented ECOG status (90.9%) had a performance status of 0 or 1, although ECOG was not documented for 32.9% of pts. The most common 1L regimen was carboplatin + paclitaxel (36.8%), followed by fluorouracil + mitomycin (20.7%). Programmed cell death protein (PD-1) inhibitor monotherapy was used in 10.7% of pts in the 1L setting. Median OS from initiation of 1L therapy was 32.4 months (95% confidence interval CI: 21.9–not reached), with a 12-month survival probability of 76.4% (95% CI: 70.3–81.3%). From the start of 1L, median rwTTD was 2.1 months (95% CI: 1.9–2.7), and median rwTTNT was 7.9 months (95% CI: 6.0–9.5). Considerable heterogeneity in treatment regimens was observed beyond 1L. PD-1 inhibitors, either as monotherapy or in combination, were administered in 28.9% of 2L and 45.8% of 3L regimens, reflecting increasing adoption of immunotherapy in later treatment lines. Conclusions: Carboplatin + paclitaxel remained the most common 1L regimen, but treatment duration was relatively short and time to subsequent therapy was modest. PD-1 inhibitors were increasingly used in later lines, highlighting the evolving integration of immunotherapy. The recent FDA approval of retifanlimab in combination with carboplatin and paclitaxel establishes a new 1L standard of care, and further real-world studies will help better understand its long-term impact on pt outcomes and treatment pathways.