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Oedema on STIR modified the effect of amoxicillin as treatment for chronic low back pain with Modic changes-subgroup
Per Martin Kristoffersen1,2, Lars C H Bråten3, Nils Vetti4,5
1Department of Radiology, Haukeland University Hospital, Jonas Liesvei 65, 5021, Bergen, Norway. per.martin.kristoffersen@helse-bergen.no.
Objective:
To evaluate potential MRI-defined effect modifiers of amoxicillin treatment in patients with chronic low back pain and type 1 or 2 Modic changes (MCs) at the level of a previous lumbar disc herniation (index level).
Methods:
In a prospective trial (AIM), 180 patients (25-64 years; mean age 45; 105 women) were randomised to receive amoxicillin or placebo for 3 months. Primary outcome was the Roland-Morris Disability Questionnaire (RMDQ) score (0-24 scale) at 1 year. Mean RMDQ score difference between the groups at 1 year defined the treatment effect; 4 RMDQ points defined the minimal clinically important effect. Predefined baseline MRI features of MCs at the index level(s) were investigated as potential effect modifiers. The predefined primary hypothesis was a better effect of amoxicillin when short tau inversion recovery (STIR) shows more MC-related high signal. To evaluate this hypothesis, we pre-constructed a composite variable with three categories (STIR1/2/3). STIR3 implied MC-related STIR signal increases with volume ≥ 25% and height > 50% of vertebral body and maximum intensity increase ≥ 25% and presence on both sides of the disc. As pre-planned, interaction with treatment was analysed using ANCOVA in the per protocol population (n = 155).
Results:
The STIR3 composite group (n = 41) and STIR signal volume ≥ 25% alone (n = 45) modified the treatment effect of amoxicillin. As hypothesised, STIR3 patients reported the largest effect (- 5.1 RMDQ points; 95% CI - 8.2 to - 1.9; p for interaction = 0.008).
Conclusions:
Predefined subgroups with abundant MC-related index-level oedema on STIR modified the effect of amoxicillin. This finding needs replication and further support.
Key Points:
• In the primary analysis of the AIM trial, the effect of amoxicillin in patients with chronic low back pain and type 1 or 2 MCs did not reach the predefined cut-off for clinical importance. • In the present MRI subgroup analysis of AIM, predefined subgroups with abundant MC-related oedema on STIR reported an effect of amoxicillin. • This finding requires replication and further support.
Insights
Amoxicillin showed a significant effect in chronic low back pain patients with abundant Modic changes-related edema on MRI. This finding in specific subgroups requires further investigation and replication.
Area of Science:
- Radiology and Imaging
- Pain Management
- Pharmacology
Background:
- Chronic low back pain (CLBP) with Modic changes (MCs) is a common condition.
- The efficacy of amoxicillin in treating CLBP with specific MRI features remains under investigation.
- Identifying patient subgroups who benefit from amoxicillin is crucial for personalized treatment.
Purpose of the Study:
- To assess MRI-defined effect modifiers of amoxicillin treatment in CLBP patients with type 1 or 2 MCs.
- To investigate whether the extent of MC-related edema on short tau inversion recovery (STIR) sequences influences amoxicillin's efficacy.
- To determine if specific MRI characteristics predict treatment response to amoxicillin.
Main Methods:
- A prospective randomized trial (AIM) involving 180 CLBP patients treated with amoxicillin or placebo for 3 months.
- Primary outcome measured by Roland-Morris Disability Questionnaire (RMDQ) score at 1 year.
- Analysis of predefined baseline MRI features, including STIR signal intensity and volume of MCs at the index level, as potential effect modifiers using ANCOVA.
Main Results:
- Amoxicillin treatment did not reach clinical importance in the overall CLBP population.
- Subgroups with abundant MC-related edema on STIR sequences (STIR3 composite group) showed a significant treatment effect of amoxicillin (-5.1 RMDQ points).
- The extent of STIR signal volume (≥25%) also modified the treatment effect.
Conclusions:
- Specific MRI-defined subgroups of CLBP patients with abundant Modic changes-related edema exhibit a positive treatment response to amoxicillin.
- These findings highlight the potential of MRI in stratifying patients for amoxicillin therapy.
- Replication and further research are necessary to validate these subgroup findings.
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