A phase 2, single arm, European multi-center trial evaluating the efficacy of afatinib as first line or later line treatment in advanced chordoma.

11517 Background: EGFR and Her2 overexpression in chordoma is well known, and chordoma cell-lines and mouse models were proven to be sensitive to EGFR inhibitor afatinib. This phase 2, single arm, European multi-center trial was designed to evaluate the efficacy of afatinib as first- or later-line tyrosine kinase inhibitor (TKI) treatment in advanced chordoma. Here we report efficacy and safety data. Methods: Eligible patients (pts) had locally advanced or metastatic, pathologically proven, EGFR expressing chordoma, not amenable for local therapies, with confirmed measurable and progressive lesions according to RECIST1.1. Pts were treated with afatinib 40mg/day in a 4 week cycle until disease progression (PD), unacceptable toxicity or withdrawal. Radiological tumor response assessment was performed every 3 cycles. The primary endpoint was response defined as progression free survival (PFS) rate ≥12 months (mos) for first-line cohort 1 and ≥ 9 mos for further-line treatment cohort 2, and change from baseline in EORTC QLQ- C30 and Brief pain inventory (BPI) questionnaires. Pts were enrolled using a Simon’s two-stage design, enrolling 13 patients in stage one, ≥3 patients with a PFS ≥ 12 or 9 mos were needed to enter stage two, where 43 pts total were to be enrolled, and ≥13 free from progression at 9 or 12 mos were required to meet the primary endpoint for success. Results: From Jun 2018 to Oct 2022, 47 pts were included. Four were ineligible for efficacy analysis (1 withdrawal, 3 stopped due to toxicity before first radiological evaluation). 34 entered cohort 1, 13 cohort 2. 31 (66.0%) were men, median age was 53 (range 28-85) years. 16 (34.0%) pts received prior systemic therapy (3 chemotherapy, 13 TKI, 2 immunotherapy, 2 other). The PFS rate at 12 mos was 40.0% in cohort 1 (12/30 pts), and 38.5% in cohort 2 (5/13 pts). Overall median PFS was 8.6 mos (95% CI 5.6-13.6); 9.1 mos (95% CI 5.8-16.6) in cohort 1 and 7.1 mos (95% CI 2.8-16.5) in cohort 2. Two pts remained on treatment at time of analysis. Best objective response by RECIST 1.1 was partial response in 4 pts (9.3%), stable disease in 33 (76.7%), PD in 5 pts (11.6%) and 1 (2.3%) unknown due to clinical progression. Median follow-up time was 23.7 mos (interquartile range 11.0-21.2). 16/47 pts (30.4%) experienced grade ≥3 adverse events (AEs). No grade 5 AEs related to afatinib were reported. Most common grade 3-4 afatinib-related AEs were skin toxicity (10.6% of pts), diarrhea (10.6%), mucositis (6.4%), hypertension (4.3%). Dose reduction was needed in 20/47 (42.6%) pts, and at least one dose interruption was needed in 31/47 (66.0%) pts. Conclusions: With a PFS rate at 12 mos of 40.0% in the first-line cohort and 38.5% at 9 mos in the further-line cohort, this phase 2 study met the PFS endpoint. QoLQ data will be provided at the conference . Partial response by RECIST was seen in 4/43 pts. Toxicity and dose reductions were relevant but manageable in most pts. Clinical trial information: NCT03083678 .