Cannabis & Oncology: What Cancer Patients Should Know

Cancer care is evolving, and so are the tools available to help patients manage symptoms and improve quality of life. One area gaining increasing attention is the therapeutic use of medical cannabis. While cannabis is not a cure for cancer, growing evidence shows it can play a meaningful role in supportive oncology—helping reduce pain, nausea, anxiety, and treatment-related side effects.

At Greenleaf Medical Clinic, we work closely with patients to ensure cannabis is used safely, effectively, and without interfering with life-saving cancer treatments.

How Cannabis May Support Symptom Management

1. Symptom Relief

Medical cannabis has been shown to help with:

  • Cancer-related pain, especially neuropathic pain
  • Chemotherapy-induced nausea and vomiting
  • Appetite loss and weight decline
  • Sleep disturbances and anxiety

Many patients report improved daily functioning and overall quality of life when cannabis is introduced as part of their supportive care plan.

2. Improved Tolerance to Treatment

By easing side effects such as nausea, appetite loss, and sleep disruption, some patients find they are better able to maintain their chemotherapy or radiation schedules.

3. Potential Anti-Tumour Effects (Preliminary Research Only)

Some preclinical studies suggest cannabinoids may have anti-proliferative or pro-apoptotic effects on certain cancer cells.

However, these findings are early, experimental, and not a substitute for proven cancer treatments. Cannabis should be viewed as complementary — never curative.

🔬 Anticancer effect of minor phytocannabinoids in preclinical models of multiple myeloma (IUBMB Journals 2025)

🔬Cannabidiol exhibits potent anti-cancer activity against gemcitabine-resistant cholangiocarcinoma (BMC Complementary Medicine and Therapies 2024)

🔬CBD + 4-F-CBD anti-tumour activity in glioblastoma cell lines (Nature Partner Journals 2024)

⚠️ Why drug interactions matter

This is the area where patient understanding is often dangerously low — and where medical oversight matters most.

Cannabis can change the way the liver processes many chemotherapy and immunotherapy drugs. This happens because cannabinoids (especially CBD) affect a family of liver enzymes called CYP450 enzymes, which are responsible for breaking down a large number of cancer medications.

1. Cannabis can LOWER levels of some cancer medications

If cannabis speeds up the metabolism of a drug:

  • The medication may become less effective
  • Treatment outcomes can be compromised
  • Cancer therapies may not work as intended

2. Cannabis can INCREASE levels of some cancer medications

If cannabis slows down metabolism:

  • Drug levels become too high
  • Toxicity and side effects become more severe
  • Patients may need treatment delays or dose reductions

3. Cannabis can interfere with immunotherapy

This is especially critical:

  • CBD may reduce certain immune responses
  • Some patients may have reduced benefit from immunotherapies if CBD is used improperly
  • Timing, dosing, and product selection matter tremendously

These interactions can occur without the patient feeling anything unusual, which is why they are so risky.

Cancer patients deserve to understand that this is not about whether cannabis is “good” or “bad” — it is about drug safety and treatment effectiveness.

Why Working With a Healthcare Professional Educated in Cannabis Medicine Matters

The idea that “CBD is always safe and THC is always risky” is outdated. The truth is:

✔ Some patients benefit most from THC-rich products
✔ Some benefit most from CBD-rich products
✔ Some need balanced THC:CBD ratios
✔ Some should avoid high CBD, especially during certain cancer therapies
✔ Some should avoid cannabis entirely during specific treatments or when immune-suppressed

Each patient’s unique situation determines what is safe and effective, including their:

  • Diagnosis and symptoms
  • Treatment plan
  • Immune status
  • Medication list
  • Overall health and tolerance
  • Goals for symptom relief

This is why specialized guidance is not optional — it is essential.

Why Greenleaf Medical Clinic Is the Right Place for Cannabis Care

Most family doctors and specialists aim to provide excellent care — but many are not trained in medical cannabis, its pharmacology, or the complexity of drug–cannabis interactions.

Cannabis medicine evolves rapidly, and general practitioners often lack current knowledge on:

  • Cannabinoid ratios
  • Dosing strategies
  • Drug–cannabis interactions
  • Product safety
  • Risks for immunosuppressed patients

This is where Greenleaf Medical Clinic provides critical support.

We are a medical cannabis expert clinic, offering specialized care for patients with a wide range of conditions — including cancer.

Our team is trained to understand:

  • How cannabis interacts with prescription medications
  • When THC, CBD, or balanced formulations are appropriate
  • When high CBD may be inappropriate or dangerous
  • How to safely adjust doses throughout cancer treatment
  • How to prevent dangerous interactions or treatment interference
  • How to support safe use in immunosuppressed or medically fragile patients

Cannabis Should Not Be Self-Directed or Based on Recreational Advice

Using cannabis without medical oversight can lead to:

  • Reduced effectiveness of critical medications
  • Excessive sedation or dizziness
  • Increased immune suppression
  • Interference with cancer therapies
  • Poor symptom control
  • Higher risk of side effects or toxicity

These risks are real — and often invisible.

Considering Cannabis as Part of Your Cancer Care?

We encourage patients and caregivers to reach out for a personalized consultation. Every cancer journey is unique, and decisions around cannabis should be tailored to your medical history, treatment plan, and overall health.

If you’re a cancer patient — especially one undergoing immunosuppressive therapy — book an appointment with our team to determine whether cannabis is a safe and beneficial option for you.