• Carlos J Roldan, Juhee Song, Mitchell P Engle, and Patrick M Dougherty.
• The University of Texas MD Anderson Cancer Center, Department of Pain Medicine, Houston, Texas; Department of Emergency Medicine, The University of Texas Health Science Center at Houston, Texas; Memorial Hermann Hospital, Lyndon Baines Johnson General Hospital, Houston, Texas.
• Pain Physician. 2017 May 1; 20 (4): 281-292.

BackgroundAngiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) have sufficient scientific support for their use as tissue protectors. Preliminary studies suggest that their angiotensin-II type 2 receptor (AT2R)-blocking properties have a beneficial profile in the treatment of neuropathic pain.ObjectivesThe purpose of the current study was to quantify the extent of the somatosensory effects of ACEI and ARB in cancer patients with chemotherapy-induced peripheral neuropathy.Study DesignWe performed a retrospective review of cancer patients with peripheral neuropathy of the upper limbs induced by known neurotoxic anti-cancer agents.SettingPain Medicine department at academic tertiary care cancer center.MethodsUsing our quantitative sensory testing (QST) data bank, we retrospectively compared the tactile function and the touch, sharp, and thermal thresholds of patients who were previously receiving ACEI or ARB for high blood pressure with these variables in controls who were not receiving ACEI or ARB.ResultsOf the 209 patients available for analysis, 145 met inclusion criteria. Baseline characteristics of patients included were generally similar. We identified 29 patients who were receiving AT2R inhibitors prior to starting chemotherapy. Touch thresholds were statistically lower in the thenar aspect of hand in the study group (patients who received AT2R inhibitors) than in the control group [mean (± SD), median 3.03 g (± 11.05), median 0.56 g and 6.75 g (± 18.28), 0.56 g, respectively (P = 0.0441)]. Similarly, the cold pain threshold was statistically higher at the thenar area for the study group [mean (± SD), median 13.23°C (± 8.02), 11.73°C] than for controls [9.89°C (± 6.62), 10.05°C (P = 0.0369)].LimitationsInadequacies in the original data acquisition and documentation of the QST and the medical records could not be addressed due to the retrospective nature of the study. Similarly, a discrepancy on the size of the comparison groups could not be reconciled. In addition, based on the available information and the lack of documented concomitant pain levels, we did not find an objective parameter able to correlate the QST findings with pain levels.ConclusionsAT2R inhibitors might offer partial and selective neuroprotective qualities of the myelinated fibers A-beta; and A-delta in cancer patients who receive neurotoxic chemotherapy.

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