(Colorectal Cancer) Is Vectibix Monotherapy Superior?

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.)

Medical Supporter was formerly certified as an international medical visa guarantor by Japan's Ministry of Foreign Affairs and the Ministry of Economy, Trade and Industry (B-066).

Figure 1

Figure 2

Figure 3

Figure 4

Related Cancer Information

• Colorectal cancer