CRYSTAL trial

Background

Phase III randomized trial in 1198 patients with EGFR-expressing metastatic colorectal cancer and no prior treatment for metastatic disease (no prior irinotecan or anti-EGFR therapy). Tested whether adding cetuximab to first-line FOLFIRI improves PFS; KRAS status assessed retrospectively.

Interventions and follow up

Arm A: Cetuximab (400 mg/m2 over 120 min C1, then 250 mg/m2 over 60 min) plus FOLFIRI every 2 weeks
Arm B: FOLFIRI every 2 weeks
Primary endpoint: Progression-free survival (PFS)
Median follow-up: 29.9 mo vs 29.4 mo, arm A vs arm B

Results

Median PFS (overall ITT): 8.9 mo vs 8.0 mo (HR 0.85, 95% CI 0.72-0.99, P=.048)
KRAS wild-type subgroup: HR 0.68 (P=.02) favoring cetuximab
KRAS mutant subgroup: HR 1.07 (P=.75) — no benefit

Adverse events

Overall (grade ≥3): 79.3% vs 61.1%, arm A vs arm B
Dermatologic: Skin reactions 19.7% vs 0.2% (P<.001); acne-like rash 16.2% vs 0.0% (P<.001)
GI/infusion: Higher grade 3-4 diarrhea and infusion-related reactions with cetuximab; treatment-related deaths similar between arms

Conclusions

Adding cetuximab to first-line FOLFIRI improved PFS and response rate in metastatic colorectal cancer, with benefit confined to KRAS wild-type tumors, validating KRAS as a predictive biomarker for anti-EGFR therapy.

Key Limitations

Overall ITT PFS benefit was modest (P=.048); KRAS analysis was retrospective and limited to exon 2 (pre-extended-RAS). EGFR immunohistochemistry, an entry criterion, was later shown not to predict benefit. Sidedness not analyzed in the original report.

Clinical Context

CRYSTAL supported FDA approval of cetuximab with FOLFIRI for first-line KRAS wild-type mCRC; the label was later restricted to RAS wild-type after extended-RAS data. ESMO guidelines endorse anti-EGFR plus chemotherapy as preferred first-line for RAS wild-type, left-sided mCRC.

References