117P - Australasian real-world treatment selection and clinical outcomes for patients with left side (LS), RAS wildtype (RASwt) metastatic colorectal cancer (mCRC)

Background

First-line (1L) treatment options for LS RASwt mCRC include the addition of epidermal growth factor receptor inhibitors (EGFRi) to chemotherapy (CT), supported by the overall survival advantage versus CT + bevacizumab (BEV) demonstrated recently in PARADIGM, the first phase 3 trial with pre-planned analysis by tumour side. Treatment selection and outcomes in Australasian routine practice has yet to be described.

Methods

Data from 1/2015 – 5/2023 on patients with LS RASwt mCRC who received 1L doublet CT for palliative intent was reviewed from TRACC, a prospective, multi-site Australasian registry. Baseline clinicopathological characteristics and survival outcomes were analysed with p ≤0.05 denoted as statistical significance.

Results

Of 676 LS RASwt, palliative intent, mCRC patients, 573 (85%) were actively treated, 404 (60%) receiving 1L doublet CT. Of these, 193 (48%) also received EGFRi and 120 (30%) also received BEV. Compared to BEV, patients receiving 1L EGFRi trended towards younger age (57 vs 61 years, p=0.07), were more often Stage IV at diagnosis (80% vs 70%, p=0.05), and less likely to have a BRAF mutant tumour (5% vs 17%, p=0.002). Median progression-free survival (PFS) was 11.7, 9.7 and 10.9 months for EGFRi + doublet CT, BEV + doublet CT and doublet CT alone respectively (HR 0.86 [0.67-1.12], p=0.06 for EGFRi + doublet CT versus BEV + doublet CT). Median overall survival (OS) was 38.1, 29.8 and 31.0 months for EGFRi + doublet CT, BEV + doublet CT and doublet CT alone respectively (HR 0.78 [0.58-1.07], p=0.12 for EGFRi + doublet CT versus BEV). Second-line (2L) PFS was similar for initial EGFRi (n=50 patients) then BEV versus opposite (n=32 patients) sequence (9.7 vs 8.0 months, p=0.55). Notably 24% of patients did not receive an EGFRi in 1L or 2L.

Conclusions

In Australasian practice, 1 in 2 patients with LS RASwt mCRC received 1L treatment with EGFRi + doublet CT, with trends toward improved PFS and OS versus BEV + doublet CT. 1 in 4 patients never received an EGFRi in 1L or 2L treatment, with further research required to understand clinician rationale for reserving active targeted treatments to later line settings.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

WEHI.

Funding

Merck.

Disclosure

V. Wong, B.B.Y. Ma: Financial Interests, Institutional, Research Funding: Merck Serono. All other authors have declared no conflicts of interest.