(Colorectal Cancer) Is Vectibix Monotherapy Superior?
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This article is a summary of international medical information and is not medical advice; it cannot replace the diagnosis or treatment plan of your attending physician. The medical technologies, drug information and clinical data presented here are compiled from public literature and official statements of major Japanese medical institutions; the applicability and outcome of any therapy vary with each patient and must be assessed individually by a qualified physician.
On July 3, 2019, Filippo Pietrantonio published in the medical journal JAMA Oncology the efficacy and safety results of anti-EGFR antibody Vectibix (panitumumab) monotherapy versus combination Vectibix + 5-FU (fluorouracil) + leucovorin as maintenance therapy in patients with RAS wild-type metastatic colorectal cancer in the VALENTINO Phase II clinical trial.
The VALENTINO Phase II trial was a multicenter, open-label, 1:1 randomized trial. It evaluated the difference between maintenance therapies in patients with RAS wild-type metastatic colorectal cancer after eight cycles of first-line combined Vectibix + FOLFOX therapy. The primary endpoint was 10-month progression-free survival (PFS):
- Vectibix monotherapy group (two-week cycle, Vectibix 6 mg/kg; N=112)
- Combined Vectibix + 5-FU + leucovorin group (two-week cycle, Vectibix 6 mg/kg + 5-FU + leucovorin; N=117)
The trial was conducted to evaluate whether, after induction therapy (combined Vectibix + FOLFOX), Vectibix monotherapy as maintenance in RAS wild-type metastatic colorectal cancer patients would be superior to the combination of Vectibix + 5-FU + leucovorin.
Patient Characteristics:
Median age — Vectibix monotherapy: 62.4 years (64–70); Combination group: 62.6 years (55–71)
Gender — Vectibix monotherapy: 66% male, 34% female; Combination: 67% male, 33% female
ECOG performance status — Vectibix monotherapy: ECOG 0: 72%, ECOG 1: 28%; Combination: ECOG 0: 72%, ECOG 1: 28%
Number of metastases — Vectibix monotherapy: 1 site 58%, >1 site 42%; Combination: 1 site 53%, >1 site 47%
Tumor location — Vectibix monotherapy: right 20%, left 80%; Combination: right 16%, left 84%
BRAF gene status — Vectibix monotherapy: wild-type 95%, mutant 5%; Combination: wild-type 97%, mutant 3%
At the time when 169 PFS events had occurred (Vectibix monotherapy 86 / combination group 83), the primary endpoint 10-month PFS rate was: Vectibix monotherapy 49% vs. combination group 59.9% — Vectibix monotherapy did not demonstrate superiority over the combination.
For other endpoints, at the time of 74 OS events (Vectibix monotherapy 34 / combination 40), the 18-month OS rate was: Vectibix monotherapy 62.4% vs. combination 66.4%. The Vectibix monotherapy group had a 13% increased hazard, with an OS hazard ratio of 1.13.
ORR was: Vectibix monotherapy 67.0% vs. combination 66.7%. Disease control rate: Vectibix monotherapy 83.9% vs. combination 82.9%, odds ratio 1.06.
Regarding safety, adverse event rates were: Vectibix monotherapy 20.3% (N=16) vs. combination 42.4% (N=36). The combination group had more frequent adverse events, including diarrhea 24.7% vs. 10.1%, and stomatitis 32.9% vs. 7.6%.
Based on VALENTINO results, Filippo Pietrantonio concluded: Vectibix monotherapy as maintenance for RAS wild-type metastatic colorectal cancer patients did not demonstrate superiority over the combination of Vectibix + 5-FU + leucovorin at the 10-month PFS endpoint.
Source: Maintenance Therapy With Panitumumab Alone vs Panitumumab Plus Fluorouracil-Leucovorin in Patients With RAS Wild-Type Metastatic Colorectal Cancer A Phase 2 Randomized Clinical Trial (JAMA Oncol. 2019 Jul 3. doi: 10.1001/jamaoncol.2019.1467.)
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