THC and CBD

Prepared 4 September 2026 by Kya at a friend's request, for her partner and the patient. It looks at cannabis-derived products (THC and CBD) two ways: as a treatment for the tumour, and as help with symptoms. Every claim is sourced in research thread 10; the strongest sources are named here. Where evidence is thin or absent it says so. It is not medical advice and nothing in it argues for changing the standard plan of biopsy, surgery and proton therapy.

The short answer

1. As a treatment for chordoma: no evidence at all. A search of the medical literature on 4 September 2026 for chordoma together with any cannabinoid returns nothing: no cell study, no animal study, no patient. The only chondrosarcoma paper is one cell line combined with a chemotherapy drug that is not used for chordoma.
2. The brain tumour science is real but it is a different tumour, and unproven in people. Laboratory work in glioma (Guzmán, Velasco and colleagues in Madrid; Scott 2014 on THC plus CBD with radiation in mice) shows cannabinoids can kill glioma cells. The one randomised human trial (Twelves 2021, British Journal of Cancer) had 21 patients with glioblastoma, and its own authors say the survival difference needs confirming. The confirming UK trial, ARISTOCRAT, has not reported. None of this transfers to chordoma.
3. Some findings point the wrong way. At the blood levels that swallowed cannabis actually reaches, THC made cancer cells grow faster in the laboratory (Hart 2004); killing needs levels far higher. THC suppressed immunity and increased tumour growth in mice (McKallip 2005). Two Israeli studies found cannabis users on immunotherapy responded less well (Taha 2019; Bar-Sela 2020).
4. Every major body says the same thing: the US National Cancer Institute, ASCO 2024, Cancer Research UK and the 2017 National Academies report all conclude cannabinoids should not be used to treat cancer outside a clinical trial.
5. For symptoms the evidence is real but modest. Sleep is the most consistent benefit, on weak trials. For nerve pain, about one person in eleven gets a 30 percent improvement (Cochrane 2018); NICE decided in 2019 not to recommend cannabinoids for chronic pain because the effect is small. Appetite trials in cancer were negative. Nabilone works for chemotherapy sickness, which is not expected for the patient.

Safety for the patient specifically

• Thinking. THC impairs memory and attention while it is being taken. This reverses with about three days off it. Given her partner's concern about losing the patient to fog, THC is the component to be wary of; CBD does not have this effect.
• Sedation. THC adds to the drowsiness of morphine and of gabapentin or pregabalin.
• Interactions. CBD blocks two liver enzymes (CYP2C19 and CYP3A4). That raises levels of carbamazepine, some opioids and dexamethasone, among others. If a nerve-pain drug or steroids are part of her plan, CBD changes their doses.
• Mood. Daily high-THC use roughly quintuples the odds of a psychotic episode in population studies; about one in ten people in the pain trials had anxiety, confusion or low mood.
• Heart. THC raises heart rate and there is a signal of cardiovascular events with heavy use.
• Surgery. Regular cannabis users need more anaesthetic and have more perioperative problems (ASRA guideline 2023). Nothing cannabis-based in the two weeks before an operation or until the surgeons say recovery is complete. Correction, 13 Oct 2026 (Kya): "two weeks" was the 4 Sep guidance and is out of date (research 31). If she uses cannabis regularly, don't stop it suddenly before the operation, because withdrawal would land on the op. Nothing on the morning of the operation, tell the anaesthetist exactly what she takes and how often, and no inhaling after nose surgery until the surgeons say so.
• Radiotherapy. Cannabinoids are antioxidants. There is a theoretical, untested concern that antioxidants could blunt radiotherapy, and separately a mouse study suggesting THC plus CBD enhanced it in glioma. Neither is evidence in humans. The proton centre should be asked and told.

The UK position in 2026

• Nothing on the NHS for the patient. The licensed products are for MS spasticity (nabiximols), two rare epilepsies (Epidyolex) and chemotherapy sickness (nabilone).
• Private clinics registered with the CQC (Curaleaf, Mamedica, Releaf and others) can prescribe balanced or high-CBD oils and high-THC products through a specialist doctor. Expect about 100 to 250 pounds a month all in.
• Shop-bought CBD is capped by Food Standards Agency advice at 10 mg a day, far below any dose used in the studies.
• High-THC oils and flower outside a prescription are Class B and their content is unknown.

If the patient wants to try it for symptoms

Reasonable, on these conditions:

1. After the histology is back and the treatment plan is fixed, not before.
2. Not in the two weeks before surgery and not until the surgical team says recovery is complete. (Corrected 13 Oct 2026: see the Surgery line above. Don't stop suddenly; nothing on the morning of the op; tell the anaesthetist.)
3. The neurosurgeon, the oncologist and whoever prescribes her pain medicines told in writing what she is taking, the dose and the pharmacy, because of the interactions above.
4. A legal prescribed product from a registered clinic, so the dose is known and a doctor is accountable.
5. CBD-dominant or balanced, started low, rather than high-THC. That follows directly from the concern about her thinking. A low-THC balanced oil at night is the usual clinic starting point for sleep.
6. A defined trial period with a measurable goal (hours slept, pain score, rescue doses used) and a decision to stop if it is not met.

Questions for the team

• Are there drugs in her plan that CBD would interact with, and would you want levels checked?
• What is your policy on cannabinoids around the operation and during proton therapy? Ask the surgeons and the proton centre separately.
• If she uses a prescribed cannabinoid for sleep or pain after recovery, will you record it and tell her GP?
• Would the pain team consider nabilone or a cannabinoid at all if standard nerve-pain treatment fails, or is the private route the only one?
• Is there any cannabinoid trial she could join? Honest answer today: none for chordoma.

Key sources

• NCI PDQ, Cannabis and Cannabinoids (health professional version); ASCO 2024 guideline on cannabis and cannabinoids in adults with cancer; Cancer Research UK; National Academies 2017 report.
• Twelves et al 2021, British Journal of Cancer (nabiximols plus temozolomide, recurrent glioblastoma). ARISTOCRAT trial, NCT05629702.
• Scott, Dalgleish and Liu 2014, Molecular Cancer Therapeutics (THC and CBD with irradiation in glioma models). Guzmán et al 2006, British Journal of Cancer (pilot in nine patients).
• Hart et al 2004, Cancer Research (low-dose cannabinoids accelerate cancer cell growth). McKallip et al 2005, Journal of Immunology. Taha et al 2019, The Oncologist; Bar-Sela et al 2020, Cancers.
• Mücke et al 2018, Cochrane (cannabis-based medicines for chronic neuropathic pain). Cochrane 2023 (cannabinoids for cancer pain). NICE NG144 (2019).
• ASRA 2023 guideline on cannabis and perioperative care. Full list with links: research thread 10, em-research/10-cannabinoids.md.