Hi,
Theoretically, randomization should enable inferences to be made relative to inter-arm differences. That is the primary point of randomization, where any inter-arm differences at baseline would be do to chance, and not patient selection bias, etc.
There was a great discussion here last year that covered issues such as baseline covariate imbalance and related topics:
That being said, there are reasons that we have more sophisticated randomization methods, beyond simple “coin-toss” approaches. These include stratified randomization, minimization, and others, to recognize that there may be a need to control the randomization process proactively, to reduce the possibility of an imbalance in one or more critical baseline factors, that may affect the analysis of primary endpoints.
in the case of your study, it seems to me that there could be potential bias resulting from differences in cancer types, locations of primary tumors and metastases, mental status (cognition, depression, etc.), and related factors, that could easily influence patient perceived pain levels over time, unless perhaps this study is for a very particular type of terminal cancer and related narrow inclusion/exclusion criteria.
That all of your patients survived at least six months, probably infers something about their characteristics when diagnosed as being terminal.
That six month time period might also infer something about differences in treatments that they may have received during that time window, each of which in turn, may have their own side effects that could impact pain levels. Those may even be post-randomization treatment decisions that could affect inter-arm differences.
In reviewing your brief description of the study, I also see a few other factors that can impact your results.
First, what kind of pain scale was used? Is this a typical 0 - 10 pain scale? If so, is a 1 point average difference after six months a clinically relevant difference, or a relevant difference in quality of life from the patient’s perspective?
Second, if you do not include the costs of medication in your assessment of the difference in cost, how can you reasonably assess that difference?
You have two groups of terminal cancer patients, who will at some point during their course, require substantial pain management, likely eventually ending up on IV narcotics, as they approach end of life. I am not sure how you can infer differences in cost, without taking into account costs associated with the utilization of pain medications, either in terms of types, frequency of use or dosing?
I am presuming that these patients are in various care environments, which have their own respective cost differentials that may bias your comparisons. Some will be inpatients in a hospital, some will be at home on an outpatient basis, while others will be in or end up in hospice care either at home or in a dedicated facility. There may be transitions from one location/state to another, as they approach end of life.
For the admissions, outpatient and emergency interactions, are you tracking the reasons for these? Are they specifically relevant to pain management interactions, or other reasons, that may bias your assessment of cost differences?
In essence, it seems to me that you have various issues to consider, relative to the identification of any differences in cost, or lack thereof, between the two arms, and what any differences identified may actually infer.
There are experts out there in pharmacoeconomics, and they can be helpful in specifically assessing costs of care in various settings.