41 – Chronic Cancer Pain Flashcards
What is cancer pain?
- Pain arising from damage to the body by cancer and from body’s response to cancer
- *best addressed by treating the cancer
- Ex. hyperalgesia, allodynia, ongoing pain, breakthrough pain
When does cancer pain become chronic?
- When cancer cannot be cured or adequately controlled
What are the mainstays of cancer treatment?
- Surgery
- Radiation therapy
- Chemotherapy
EXAMWhat is the primary goal of palliative radiation treatment?
- Alleviate pain or discomfort associated with an incurable tumor
- clear definition of palliative intent cancer treatment with radiation
Osteosarcoma and mechanical stimulation (tumor)
- Increased pressure within in
- Microfractures
- Stretching of periosteum
- Compression of nerves due to collapse of bone
- Reactive muscle spasm
- Nerve root infiltration
Osteosarcoma and chemical stimulation (tumor and body)
- Prostaglandins
- Inflammatory cytokines (Ex. GFs, interferons, CSFs)
Canine appendicular osteosarcoma
- Most COMMON primary bone tumor
- Locally invasive to highly metastatic to distant sites
o By the time you see them 95% have metastaized
What is the definitive treatment of canine appendicular osteosarcoma?
- Surgery (amputation, limb spare) OR
- Radiation for primary tumor
- Chemotherapy to delay distant metastases
EXAMRank the effectiveness of pain relief for radiation, surgical and medical therapies for canine osteosarcoma
- Amputation removes source of pain
- Stereotactic radiation therapy (SRT) alleviates pain
o Reduces mechanical and chemical stimulation of nociceptors
EXAMHow do dog owners feel about amputation for canine osteosarcoma?
- Very happy: 98%
- Even if the animals did not live long afterwards, they did not mind it
- *quality of life!
What are some reasons for not doing amputation or SRT?
- Owners do not want to
- Patient NOT a good candidate for amputation
- Recurrent tumor
- Metastatic to other bones
- *multimodal analgesia and multimodal treatment
EXAMWhich pain-relieving drugs are best suited to long-term, outpatient pain control?
- Metacam
- Gabapentin
- Amantadine
- Zoledronate (EXPENSIVE)
- *details to come
Drugs to decrease inflammation
- NSAIDs inhibits COX
o *first drug used for cancer pain! - Meloxicam, deracoxib
- Grapiprant
- NOT used in patients that are on a steroid
- *generally well tolerated, narrow range of dosing, EXPENSIVE ($85/month)
Drugs to decrease pain signal transmission
- Gabapentin ($38/month)
- Amantadine ($70/month)
What are other pain drugs
- Tramadol
- Fentanyl patches
- Bisphosphonates
Tramadol
- Mu agoinst, alpha 2 agonist
- *serotonin reuptake inhibition
- Side effects: sedation, agitation
- Do NOT use with SSRI
- Efficacy is questionable
- Expensive ($176/month)
Fentanyl patches
- Side effects: sedation, agitation, inappetence, dysphoria
- *use in outpatients can be challenging
- Can de difficult to distinguish between side effects and pain
Bisphosphonates
- Induces apoptosis of tumour cells
- Inhibits tumour cell proliferation
- Antiangiogenic
- Renal effects, low risk of bone necrosis
- In-hospital administration: expensive
- Ex. Zoledronate (especially for bone disease)
EXAMWhat are the indications to palliative radiation treatment of chronic cancer pain (e.g., canine osteosarcoma)?
- Goal to alleviate pain or discomfort from an incurable tumour?
- Does pet’s family fully understand the goal of treatment?
- Is the tumour the source of clinical symptoms?
- Is the patient’s condition stable enough for radiation treatment?
EXAMWhat are the contraindications to palliative radiation treatment of chronic cancer pain (e.g., canine osteosarcoma)?
- Probability of pain improvement is low and euthanasia is recommended
- *Metastatic disease (distant or regional) is NOT a contraindication to treatment
o Ex. lung mets=do NOT cause pain
How does radiation therapy work?
- Photons (x-rays) damage DNA leading to cell death
- Direct killing of tumour cells
- Direct killing of host cells
- *decrease in mechanical and chemical stimulation of nociceptors
Outcome of palliative radiation with osteosarcoma
- Pain relief ranges from 2-4 months
- Median survival: 4-10months
- 74-96% experience pain relief
Outcome of palliative radiation with canine oral melanoma
- Overall response rate of 80%
o 50% complete remission
o 30% partial remission - median survival: 8 months
Outcomes of palliative radiation therapy: overall
- do NOT look at survival time for ‘relief’ of pain
o very owner influenced! - Need pain scales
- *best endpoint to assess success of treatment of chronic pain=quality of life
