Many patients with cancer pain have pain not fully controlled on opioids (eg. morphine). The addition of acetaminophen (Tylenol) to opioids in a small study in cancer patients demonstrated better pain control without an increase in side effects. This study will determine if regular acetaminophen improves pain control when added to strong opioids in patients with cancer pain.

Aim:

To assess whether regular oral acetaminophen can reduce pain in cancer patients already on a strong opioid regimen.

Rationale:

It is estimated that 75% of people with advanced cancer suffer significant pain. Many of these people continue to have pain despite being on strong opioids. The rationale behind adding an additional analgesic with a different mechanism of action is to attempt to improve analgesia without increasing side effects.

Overview:

This is a double blind, randomised placebo-controlled, crossover trial to evaluate whether the addition of regular acetaminophen can reduce pain in cancer patients already on a strong opioid regimen. The study will be performed in ambulatory cancer patients who have pain that is believed to be caused by their cancer, and who have already been stabilised on an opioid regimen of > 60mg/day of morphine equivalents. Each patient will be randomly allocated to receive either acetaminophen 1g qid or an identical appearing placebo qid for a seven-day period, and then crossed over to the other arm for a further seven-day period. Patients will complete daily pain diaries and weekly questionnaires (Brief Pain Inventory) and comparison will be made between the pain scores for the two treatment periods. Patient preference for the two treatment periods will also be evaluated.

Research Question:

A randomised, double-blind, placebo controlled crossover trial to determine if the addition of regular acetaminophen (1g PO qid) leads to improved analgesic control in adult cancer patients at Princess Margaret Hospital, who are already on strong opioids (> 60mg morphine equivalents/day) as evaluated by daily pain scores measured by Numerical Rating Scales (NRS) and the Brief Pain Inventory (BPI).

Hypothesis:

Regular acetaminophen improves pain control in cancer patients who are already on strong opioid regimens.

Inclusion Criteria:

1. Patients diagnosed with malignancy who have persistent pain which is believed by the investigator to be due to their cancer, and whose analgesic regimen has been stabilised on > 60mg of morphine equivalents/day.
2. Age > 18 years
3. Performance status of 0-2 by the European Co-operative Oncology Group (ECOG) Performance Scale
4. Sufficient English skills to be able to complete the daily diary, BPI and to understand the consent form
5. Signed informed consent

Exclusion Criteria:

1. Patient has no pain (0/10 on NRS).

2. Patients with severe pain are excluded, however once their pain control is optimised they are eligible.

3. Patient has received radiation therapy in the six weeks prior to commencing the study or is likely to require radiotherapy during the study period.

4. Patient has commenced, or had dose modifications, to either non-steroidal anti-inflammatory drugs (NSAIDs) or corticosteroids in the week prior to commencing the study, or during the two-week study period.

5. Patient has commenced chemotherapy or hormone therapy in the 4 weeks prior to the study or is expected to commence chemotherapy or hormonotherapy during the study period. Patients who are stable on long-term chemotherapy or hormones are eligible for this study. Patients who receive high dose steroids as antiemetics with their chemotherapy are eligible providing they are not receiving the steroids during the study period.

6. Patient has a contraindication to acetaminophen.

7. Use of acetaminophen in the 48 hours prior to commencement of the study period.

8. Abnormal laboratory values:

   • Absolute neutrophil count < 1.5 X 10^9/L and white blood cell (WBC) count < 3 X 10^9/L
   • Platelet count < 100 X 10^9/L
   • Liver transaminases > 2.5 X upper limit of normal
   • Bilirubin > 1.5 X upper limit of normal
   • Creatinine > 1.5 X upper limit of normal