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Bottom line
This study suggests that trigger point injection with local anesthetic can help manage pain in people with incurable cancer, and it might work better when patients expect it to.
Preliminary evidencePublished
Evidence hierarchy
Study participants
Patients with incurable cancer experiencing myofascial pain syndrome
Words decoded
- myofascial pain syndrome (MPS)
- — A type of pain caused by sensitive spots in muscles called trigger points.
- trigger point injection (TPI)
- — A procedure where a doctor injects medicine into a trigger point to help reduce pain.
- numerical rating scale (NRS)
- — A scale used to measure pain intensity, where 0 is no pain and 10 is the worst possible pain.
Study Summary
Background
This study examined whether the immediate pain relief experienced after trigger point injections affects how well patients respond to treatment over the following week. Previous research showed that patient expectations can influence treatment outcomes, but it was unclear whether immediate pain relief creates positive expectations that lead to better long-term results. The researchers focused on cancer patients with myofascial pain syndrome, a condition where muscle trigger points cause significant pain and are common in advanced cancer.
What They Did
The researchers followed 205 cancer patients who received trigger point injections with local anesthetic (1ml of 1% lidocaine) for myofascial pain. They measured pain levels and expectations before treatment, immediately after, and at 1, 3, and 7 days post-injection. Patients were divided into two groups: those who experienced immediate pain relief (33% or greater reduction within 5-20 minutes) and those who did not. The team used sophisticated statistical analysis called path analysis to understand how immediate effects, expectations, and pain outcomes were connected.
What They Found
Of the 205 patients, 58.1% experienced immediate pain relief after injection. This immediate effect group had dramatically better outcomes at 7 days: 88.2% showed meaningful pain reduction compared to only 39.5% in the non-immediate effect group. The immediate effect group also developed higher expectations for pain relief that lasted throughout the week. The path analysis revealed that immediate pain relief influenced long-term outcomes both directly and indirectly through increased patient expectations.
The indirect effect through expectations was actually stronger than the direct effect, suggesting that the psychological boost from immediate relief is crucial for sustained improvement.
What This Means
This research provides important evidence that the immediate response to trigger point injections predicts how well patients will do over the following week. For clinicians, this suggests that achieving immediate pain relief during the procedure may be critical not just for immediate comfort, but for setting up positive expectations that support ongoing recovery. This finding could help doctors better predict which patients will benefit most from trigger point injections and potentially guide decisions about treatment approaches. For patients, experiencing immediate relief after injection is a positive sign that the treatment will likely continue helping over the next week.
205
n=119
Experienced ≥33% pain reduction within 5-20 minutes
n=86
Did not experience immediate pain relief
Immediate Effect
Experienced ≥33% pain reduction within 5-20 minutes
Non-Immediate Effect
Did not experience immediate pain relief
Results Comparison
Pain Reduction Rate at 7 Days
%Key Findings
| Finding | Detail | Impact |
|---|---|---|
| Immediate pain relief strongly predicted 7-day outcomes | 88.2% of immediate effect group vs 39.5% of non-immediate group had pain reduction at 7 days | High |
| Expectations mediated the relationship between immediate and sustained effects | Path analysis showed indirect effect through expectations (β=0.285) was stronger than direct effect (β=0.194) | High |
| Over half of cancer patients experienced immediate relief | 58.1% (95% CI: 51.2-64.9) had immediate pain reduction ≥33% after trigger point injection | Medium |
| Increased expectations were maintained throughout follow-up | Immediate effect group maintained significantly higher pain relief expectations at all time points | Medium |
| No adverse events occurred | All 205 trigger point injections were completed without complications during evaluation period | Medium |
88.2% of immediate effect group vs 39.5% of non-immediate group had pain reduction at 7 days
Path analysis showed indirect effect through expectations (β=0.285) was stronger than direct effect (β=0.194)
58.1% (95% CI: 51.2-64.9) had immediate pain reduction ≥33% after trigger point injection
Immediate effect group maintained significantly higher pain relief expectations at all time points
All 205 trigger point injections were completed without complications during evaluation period
Strengths
- Large sample size of 205 cancer patients
- Sophisticated path analysis to understand causal relationships
- Clear operational definitions for immediate effect and pain reduction
- Comprehensive assessment of expectations and pain outcomes
- No adverse events reported
Limitations
- Observational study design limits causal inferences
- Single-center study may limit generalizability
- Short 7-day follow-up period for cancer patients
- Expectations questionnaire validity not established
- Limited to patients with incurable cancer
Key Takeaways for Patients
What This Means for You
- 01If you feel immediate pain relief after a trigger point injection, you're likely to continue feeling better over the next week
- 02The immediate response to treatment can help boost your confidence and expectations, which may enhance the treatment's effectiveness
- 03Trigger point injections appear safe in cancer patients with no serious side effects reported in this study
- 04About 6 out of 10 cancer patients experience immediate pain relief from trigger point injections
- 05Your response in the first 20 minutes after injection may help your doctor predict how well the treatment will work for you
Read the Full Paper
Access the complete peer-reviewed study from Frontiers in Psychiatry
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