Evaluating neuropathy after breast cancer surgery – QST or bedside examination?
Breast cancer affects approximately 13% of women in their lifetime in the US. Treatment for breast cancer varies between surgery, radiation, immunotherapy, hormonal therapy and chemotherapy, and often includes a combination of interventions.
Breast cancer survivors who have undergone surgical removal of cancerous tissue, may cope with long-lasting sensory deficits and neuropathic pain at the surgery site, in part associated with the type of surgery, and often due to the handling of the intercostobrachial nerve (ICBN) during surgery.
QST & neuropathic pain, study design
Sensory deficits may be mapped and quantified using bedside examinations (BE) and quantitative sensory testing (QST), respectively. In a 2020 publication, Mustonen et al. have set out to characterize sensory function in breast cancer survivors suffering from neuropathic pain several years post-surgery. Additionally they aimed to assess what added value QST might have over bedside examinations in this patient group.
QST was performed according to the protocol of the German Research Network on Neuropathic Pain (DFNS). Medoc’s TSA-II served as the device for measuring warm and cold sensation, thermal sensory limen, paradoxical heat sensations, heat and cold pain. This protocol also included pressure pain testing, vibration testing, and mechanical testing. Bedside examination included testing light touch, dynamic mechanical allodynia, static allodynia, sharp touch, and warm and cold sensation
For QST, patients were tested bilaterally (within the surgery site on the site where the most intense complaints for neuropathic pain were, and on its contralateral mirror site), and their thresholds were compared to the nearest body site on the trunk that had DFNS reference data. QST was performed of the breast (n=43), or on the ICBN site (n=61), depending on where the most neuropathic complaints were.
QST and Bedside examination
One hundred and four patients underwent QST and BE. Results show a significant sensory loss of function for most of the QST items; however, vibration and PPT showed a significant gain of function. Interestingly, on the unaffected side, loss of function was also found for the following parameters: thermal and mechanical sensory detection thresholds and thermal sensory limen. When both sides were compared to each other in terms of QST there were significant differences between all thermal thresholds (sensory and pain) and mechanical detection and pain thresholds, irrespective of testing site (breast or ICBN site).
When comparisons were made in the levels of handling of the ICBN, i.e.; spared, partial or total resection, it was found that the only difference of statistical significance was between the spared and the total resection on mechanical detection thresholds.
Standardized protocols, area coverage, and resolution
There were inconsistencies, and in specific corresponding tests, relatively little overlap between the results of the BE and of the QST. BE and QST differ by the methodology and area they could cover. QST, with more sophisticated equipment and standardized protocols, can cover a smaller area, but its results may have a higher resolution on deficits in functionality than do those of BE. Bedside examination, on the other hand, can be used to map a large area of interest and find the major points of deficit in sensory function.
In such, BE and QST are complementary methods of neurological evaluation, rather than substitutes.