Cannabinoid use alongside dual immunotherapy was not associated with worse cancer treatment outcomes | Research

The takeaway

In a pooled analysis of 684 cancer patients treated with dual immune checkpoint inhibitors, cannabinoid use was not associated with worse survival or increased adverse events, and was linked to improved progression-free survival by one measure.

Oncologists, cancer patients considering cannabinoid use during immunotherapy, and palliative care clinicians.

No harm to immunotherapy outcomes

What the researchers found

Of 684 patients, 9.5% used cannabinoids during treatment. By multivariate analysis, baseline cannabinoid use was significantly associated with improved iPFS (p=0.05) but not with iBOR, PFS, OS, or incidence of immune-related adverse events. Results were similar when analyzed by cannabinoid use at any time during trial.

Why it matters

There is concern that cannabinoids could impair immune checkpoint inhibitor effectiveness by inhibiting T-cell activation. This pooled analysis provides reassurance that cannabinoid use did not worsen outcomes in patients receiving dual immunotherapy.

The numbers in context

N = 684 patients. 65 (9.5%) used cannabinoids at any time on trial. 32 (4.7%) at baseline. Baseline cannabinoid use associated with improved iPFS (p=0.05). No significant differences in OS (p=0.35), PFS (p=0.12), grade 1-4 irAEs (p=0.65-0.96).

How the study worked

Pooled individual patient data from 4 Canadian Cancer Trials Group (CCTG) trials of patients receiving dual immune checkpoint inhibitors (durvalumab plus tremelimumab) with or without chemotherapy. Cochran-Mantel-Haenszel and log-rank tests stratified by trial/treatment arm.

What this study cannot tell us

Observational analysis within clinical trials. Small number of cannabinoid users (n=65) limits power. Self-reported cannabinoid use without standardized dosing or product information. iPFS improvement did not translate to OS benefit.

How to read the evidence

Pooled analysis of clinical trial data provides stronger evidence than single observational studies, but small number of cannabinoid users and self-report limitations reduce certainty.

When this study was published

2025 publication

The bigger picture

As more cancer patients use cannabis alongside immunotherapy, evidence on safety becomes increasingly important. This study adds to a growing body of data suggesting cannabinoids do not undermine immunotherapy effectiveness.

Questions still open

Could cannabinoids have a biological benefit for immunotherapy response, or is the iPFS finding a statistical artifact? Would higher cannabinoid doses or specific cannabinoid types affect outcomes differently?

Common questions

Can cancer patients safely use cannabis during immunotherapy?

This pooled analysis of 684 patients found no negative impact of cannabinoid use on survival, treatment response, or adverse event rates during dual immune checkpoint inhibitor therapy. One measure even showed improved progression-free survival.

Why is there concern about cannabis and immunotherapy?

Immune checkpoint inhibitors work by activating T cells against cancer, while some cannabinoids can suppress T-cell activation. Theoretically, this could reduce immunotherapy effectiveness, but this study did not find evidence of that.

Read the original research

Effects of cannabinoids on immune checkpoint inhibitor response: CCTG pooled analysis of individual patient data.

Immunotherapy, 17(4), 257-268

View on PubMed ↗Publisher’s paper ↗

Citation

Coschi, Courtney H; Ding, Keyue; Tong, Justin; Tu, Dongsheng; O'Callaghan, Christopher; Leighl, Natasha B; Vera-Badillo, Francisco; Juergens, Rosalyn A; Hao, Desiree; Seymour, Lesley; Renouf, Daniel J; Chen, Eric; Gaudreau, Pierre-Olivier; Fung, Andrea S. (2025). Effects of cannabinoids on immune checkpoint inhibitor response: CCTG pooled analysis of individual patient data.. Immunotherapy, 17(4), 257-268. https://doi.org/10.1080/1750743X.2025.2485012