Pre-defined research questions / hypothesis and endpoints:
Main objective and endpoint: To evaluate the effect of Amoxicillin versus placebo on
disease-specific disability evaluated by the Roland Morris Disability Questionnaire (RMDQ) at
one year (12 months) follow-up in patients with chronic LBP and MCs type I or II adjacent to
a previously herniated disc (Hypothesis A).
Thus, the projects Main objective is to re-examine the clinical effect of antibiotic
treatment reported in the former Danish study at one year (12 months) follow-up.
Investigators will use the same primary outcome measure (RMDQ), but the effect will be
evaluated in patients with MCs type I or MCs type II since, as outlined above, investigators
argue that some MCs type I patients may be classified as MCs type II patients and vice versa
dependent on the magnet strength of MRI machines used, and MCs type I and type II most likely
represent a common process (that can be influenced by a common treatment) (hypothesis A). As
a secondary objective (SO 1) investigators will evaluate the effect of Amoxicillin versus
placebo on RMDQ at one year (12 months) follow-up separately in patients with type I and type
II MCs, respectively (hypotheses B and C).
Exploratory and key supportive objectives (KSOs) and endpoints):
KSO 2. To evaluate the effect of Amoxicillin versus placebo on Oswestry Disability Index
(ODI) at one year (12 months) follow-up in the whole cohort of included patients
(hypothesis D).
KSO 3. To evaluate the effect of Amoxicillin versus placebo on LBP intensity at one year
(12 months) follow-up in the whole cohort of included patients (hypothesis E).
KSO 4. To evaluate whether the short tau inversion recovery (STIR) signal (intensity and
extent) of MCs on baseline MRI predicts change in RMDQ from baseline to one year (12
months) follow-up (hypothesis F).
KSO 5. To assess whether change in STIR signal (intensity and extent) of MCs at one year
(12 months) follow-up is related to change in RMDQ from baseline to one year (12 months)
follow-up (hypothesis G).
KSO 6. To evaluate the effect of Amoxicillin versus placebo on health-related quality of
life (the EQ-5D) at one year (12 months) follow-up in the whole cohort of included
patients (hypothesis H).
To evaluate cost-effectiveness of Amoxicillin versus placebo at one year (12 months)
follow-up in the whole cohort of included patients.
To evaluate whether positive pain provocation tests at baseline predicts change in RMDQ
at one year (12 months) follow-up.
To evaluate the difference in incidence of AEs and SAEs between the two intervention
groups from inclusion to one year (12 months) follow-up in the whole cohort of included
patients.
To evaluate, separately in the two intervention groups, whether lack of a clinically
important improvement in RMDQ, ODI, and LBP intensity, respectively, from baseline to
post-treatment (100-das after start of treatment) is associated with lack of a
clinically important improvement in these outcomes from baseline to one-year (12 months)
follow-up.
Further clinical objectives and endpoints: To evaluate the effect of Amoxicillin versus
placebo on:
RMDQ at one year (12 months) follow-up separately in patients previously undergoing
back surgery for disc herniation and patients NOT previously undergoing back
surgery for disc herniation.
other outcome measures not mentioned above (leg pain intensity, hours with LBP
during the last 4 weeks, bothersomeness, days with sick leave, co-interventions,
patients' satisfaction, global perceived effect) at one year (12 months) follow-up
in the whole cohort of included patients
secondary outcome measures at one year (12 months) follow-up separately in patients
with type I and type II MCs at baseline, respectively
primary and secondary outcomes measures posttreatment (100 days after start of
treatment) in the whole cohort and separately in patients with type I and type II
MCs at baseline, respectively.
Further radiological objectives and endpoints: To assess whether characteristics of MCs
on baseline MRI predict change in ODI, or change in intensity of LBP from baseline to
one year (12 months) follow-up. To compare change in characteristics of MCs from
inclusion to one year (12 months) follow-up between treatment groups, and to assess
whether this change in MCs is related to change in RMDQ, ODI, and pain intensity from
baseline to one year (12 months) follow-up. To determine the reliability of different
MCs characteristics by different MRI methods. To assess the relationships of these MC
characteristics to each other and to clinical variables.
Genetic objectives and endpoints: To investigate the effect of Amoxicillin on epigenetic
patterns, longitudinal gene- and protein expression, genetic variation, from baseline to
post-treatment (100 days after start of treatment) and from baseline to one year (12 months)
follow-up in patients with MCs type I or II, and to evaluate correlations with clinical data.
Randomization lists will be created using STATA 13 (StatCorp LP, College Station, TX, USA)
and will be stratified by MODIC type (1/2) and previous surgery (yes/no) with a 1:1:1:1
allocation and random block sizes of 4 and 6. This will ensure similar numbers of patients
receiving antibiotics or placebo within each stratum (1-MCs type I, no previous back surgery
for disc herniation, 2-MCs type I, previous back surgery for disc herniation, 3-MCs type II,
no previous back surgery for disc herniation, and 4-MCs type II, previous back surgery for
disc herniation). Investigators intend to recruit two equally large patient groups, one with
type I MCs and one with type II MCs, in order to evaluate treatment effect separately in each
MC type group and not only in the total sample. Investigators will achieve this by stratified
randomization as explained above, and investigators will stop the inclusion of the two MCs
type II strata (with and without previous surgery) when investigators have enough MCs type II
patients, and continue the inclusion of the two MCs type I strata (or vice versa). Patients
are stratified for previous back surgery for disc herniation (Yes/No) since it is not clear
how the low virulent anaerobic organisms gain access to the disc (during normal bacteraemia
or as a result of intraoperative contamination). Hence, stratifying for previous back surgery
for disc herniation will ensure balanced distribution of this potential source of infection
between groups.
Investigators have designed the study with enough power to evaluate the treatment effect
separately in the MC type I group and in the MC type II group (investigators will include
equally many Modic I and Modic II patients in the trial), but the main analysis will be in
the whole cohort of patients with MCs type I or II. In power calculations for each MC type
group, investigators used a two-sided alfa of 0.05 and a power of 0.90 and wished to be able
to identify a difference in mean RMDQ of 4 (SD 5) between the two treatment groups at 12
months follow-up. The minimal important difference in mean RMDQ between groups is not clear,
but a change in RMDQ of 2-3 in individual patients over time is very unlikely to be important
and may represent measurement error. Investigators therefore used a difference of 4 in mean
RMDQ between groups in the power calculations. The SD of 5 is within the upper range of
commonly reported SDs for RMDQ in patients with persistent LBP.
A to-sided alfa 0.05 (i.e. 95 % Confidence Interval), a power 90, ratio of sample size 1
(antibiotic group / placebo group) and a difference in RMDQ 4 (SD 5) results in a sample size
of 33 in each treatment group, or 66 in both treatment groups; i.e. 132 in the total sample
(both MC type groups). The Danish RCT by Albert et al 2013 had 11 % dropouts. Adding 20 % for
dropouts (26 patients) investigators calculated that they need to include 158 patients in the
study, rounded up to 160 patients: 80 patients with type I MCs and 80 patients with type II
MCs. The study continue inclusion until 80 patients are included in the MC type group that is
slowes to recruit, implying inclusion of at least 80 patients in the other MC type group and
at least 160 patients in total.
Data on main outcome will be analysed by a statistician who is blinded to group status. The
primary analyses (main outcome) will be by intention-to-treat in the whole cohort of patients
with MCs type I or II using an ANCOVA analysis adjusted for baseline RMDQ-score. The
significance level will be 0.05. Investigators will report the p value with 95 % CI. ANCOVA
analysis, adjusted for baseline RMDQ-score, will also be used to examine main outcome
separately in the sub-samples of type I and II MSc. The significance level will still be
0.05. Investigators will report the exact p value with 95 % CI for each of the two
sub-samples. For the secondary outcome measures also ANCOVA analysis will be used with
adjustment for baseline values and in accordance to intention to treat (ITT). The analysis
will be carried out in the whole cohort of patients with MCs type I or II with a significance
level of 0.05, and separately in the two sub-samples of type I and II MSc. Investigators will
report the p value with 95 % CI. Analyses of MRI results will include observer agreement
analyses (kappa, McNemars test, Bland Altmann plots) and multiple regression analyses to
assess relationships with clinical variables.
As secondary analysis, investigators will perform responder analyses of RMDQ to supplement
the interpretability of the main analysis. They will analyze if a higher proportion of
patients with MCs type I or II at baseline reports a clinically relevant improvement of their
RMDQ-score from baseline to one year (12 months) follow-up in the antibiotic treatment group
than in the placebo group. Analysis (chi-square test) will be performed for three different
cut-offs (>75%, >50% and >30% improvement of RMDQ score from baseline to one year follow-up,
respectively). Intention-to-treat (ITT) principles will be used and the significance level
will be 0.05. Investigators will report the exact p value and the number needed to treat
(NNT) with 95 % CI.
Analyses of MRI results will include observer agreement analyses (kappa, McNemars test, Bland
Altmann plots) and multiple regression analyses to assess relationships with clinical
variables. Cost-effectiveness will be analyzed as the difference in costs between the 2
treatment groups divided by their difference in QALYs gained. The results will be presented
as an incremental cost-effectiveness ratio (ICER).
In addition to outcome measured listed, the following will be evaluated:
To check Blinding: Patients will be asked which study medicine (Amoxicillin / placebo /
unsure) they think they received. Points of time: post-treatment (100 days after start
of intervention), and one year (12 months) after start of intervention.
To evaluate Compliance to the medicine protocol; Patients will be asked every week
during the intervention period how many days the last week they took the study
medication (0-7)). At post-treament (100 days after start of treatment); Capsule count
will be performed by a pharmacist.
Adverse events will be Registered and CTC-coded at every study visit (=monthly) during
the intervention period by the principal investigators.
EudraCT no: 2013-004505-14