Food intervention trial to reduce immunotherapy toxicity (FORX): Impact of a weekly 30-plant diet on immune related adverse events

FORX

Patient / Population Intervention / Exposure Comparison Outcome

In patients with solid tumours starting immune checkpoint inhibitors, a 30-plant-per-week diet over 12 weeks was feasible and was followed by at least one irAE in 51.9% and grade ≥3 toxicity in 3.7% in a single-arm study without a comparator.

N

—patients

Design

Prospective, single-arm interventional study at UZ Brussel, a Belgian tertiary oncology centre, of a 30-plant-per-week diet during the first 12 weeks of immune checkpoint inhibitor treatment in patients with solid tumours (NCT05832606).

Endpoint

Incidence of immune-related adverse events (irAEs) over the first 12 weeks of immune checkpoint inhibitor treatment.

ResultAt least one irAE over 12 weeks in 28 of 54 evaluable patients (51.9%; 95% CI 38.9-64.6%). Grade ≥3 toxicity in 2 (3.7%; 95% CI 1.0-12.5%). Systemic immunosuppression required in 6 (11.1%; 95% CI 5.2-22.2%). Mean fibre intake rose from 20.2 g/day at baseline to 28.8 g/day during the intervention, a mean within-patient increase of 8.5 g/day (95% CI 6.7-10.4; paired t-test, P<.001). Of 47 patients analysed to date, 35 (74.5%) achieved a mean fibre intake ≥25 g/day.

Verhaert M, Demol J, Aspeslagh S. Presented at ESMO Congress 2026, abstract LBA93, 25 October. Not yet published.

Discussion & critique

This single-arm study shows that a 30-plant-per-week diet can be delivered alongside immunotherapy and raises fibre intake. Without a control group, the irAE rate cannot be attributed to the diet: patients received a mix of anti-PD(L)1 monotherapy and combinations, and the window was only 12 weeks. Only 54 patients were evaluable after 7 early discontinuations, and fibre data cover just 47. The abstract reports neither adherence to the 30-plant target itself nor the secondary endpoints of gut microbiome composition and oncological response.