What a $3.2 Million NCI Study Will Examine About Cannabis and Cancer Immunotherapy
A $3.2 million grant from the National Cancer Institute is supporting a University at Buffalo-led study of how cannabis use may affect people receiving immune checkpoint inhibitor therapy for cancer. The project is designed to examine both potential benefits and harms—not to test cannabis as a cancer treatment.
The NCI-funded prospective cohort study is led by psychologist Rebecca Ashare, PhD, in collaboration with Thomas Jefferson University and Oregon Health & Science University. The research is part of a broader NCI initiative examining cannabis and cannabinoid use among adults undergoing cancer treatment.
Immune checkpoint inhibitors are medications that help the immune system recognize and attack cancer cells. Because cannabis and its cannabinoids can influence immune and inflammatory activity, researchers are investigating whether regular use could affect treatment response, symptoms, quality of life, or adverse effects.
The study is observational rather than randomized. According to its ClinicalTrials.gov record, investigators plan to enroll 450 adults—about 150 at each participating site—including cannabis users and people who do not use cannabis. Participants will continue using their own cannabis products rather than receiving a standardized study formulation.
Each participant will be followed for 12 months. Researchers will collect information through repeated surveys and symptom assessments, review electronic medical records, and examine outcomes such as pain, sleep disturbance, anxiety, quality of life, concentration, memory, dizziness, and fatigue. A smaller group of 60 patients who have not yet started immune checkpoint inhibitor treatment will also provide blood samples to help researchers study inflammatory and immune markers.
The project will also examine whether neighborhood conditions and access to cannabis are associated with differences in symptoms or treatment outcomes. That analysis could help researchers determine whether social and economic disadvantage shapes patients’ ability to use cannabis—or influences the risks and benefits they experience.
Earlier studies have raised concerns but cannot establish that cannabis causes poorer cancer outcomes. For example, an observational study published in 2020 reported shorter time to tumor progression and overall survival among some cannabis users receiving immunotherapy. Because patients were not randomly assigned to use cannabis, differences in disease severity, symptoms, other treatments, or overall health could have contributed to the findings.
That uncertainty is reflected in the American Society of Clinical Oncology guideline on cannabis and cannabinoids in adults with cancer, which says the evidence for most uses is limited or of low certainty. The guideline recommends against using cannabis or cannabinoids as a cancer-directed treatment outside a clinical trial, while noting that some cannabinoid medicines may help with chemotherapy-induced nausea and vomiting when added to standard antiemetic treatment.
The UB study began enrolling participants in January 2025 and is expected to continue through 2027. Its results could give patients and oncology teams more reliable information about whether cannabis helps manage symptoms during immunotherapy, carries meaningful risks, or is associated with changes in treatment response. Until those data are available, patients receiving immunotherapy should discuss cannabis use with their oncology team rather than assume that it is harmless or therapeutically beneficial.
