Quantitative sensory testing (QST), a set of noninvasive methods used to assess sensory and pain perception, has been used for three decades. The precision of the instruments and the uninvasiveness encouraged many QST-based trials. The developments made have benefited multiple disciplines. QST relies on analysis of an individual's response to external stimuli, reflecting the integrity of the PNS and the sensory pathway. The sensory pathway cannot be assessed in isolation from the affective and cognitive characteristics of patients or testers. Many variables potentially affect the reliability and reproducibility of QST, which after all, is designed for the testing of individuals by other individuals. Several decades of QST research have yielded exciting contributions, but the future of QST cannot be fully known.

Background: Oral mucositis is a complication of cancer therapy, causing severe pain that affects oral functioning, nutrition, and quality of life, as well as therapy nonadherence or dose-limiting toxicity. Anecdotal experience has suggested that methylene blue (MB) oral rinse may be an effective and safe treatment of this oral pain. Methods: To evaluate the efficacy and safety of MB oral rinse for the treatment of oral pain due to mucositis in patients with cancer, we retrospectively evaluated patients who experienced refractory pain despite conventional therapy. Results: We identified 281 patients who received MB oral rinse. Most were receiving treatment for leukemia (n=85; 30.3%) and head and neck squamous cell carcinoma (n=84; 29.9%). The most common treatments were radiation therapy alone (n=108; 38.4%) and chemoradiation (n=86; 30.6%). Median duration of symptoms was 14 days. Mean (SD) numeric rating scale pain scores were 7.7 (1.83; median, 8) before MB oral rinse and 2.51 (2.76; median, 2) after MB oral rinse (P<.0001). Most patients achieved pain control within the first 3 doses. The effectiveness of MB oral rinse was independent of patient age, sex, cancer type, cancer stage, MB dilution, and pain duration or baseline pain scores. The lowest response to treatment was reported in individuals with esophageal mucositis. Few patients experienced adverse effects of MB oral rinse (n=13; 4.6%); 10 had a transient burning sensation, 2 had transient blue discoloration of the teeth and mouth, and 1 had increased pain. Conclusions: MB oral rinse is an effective and safe treatment for refractory pain from oral mucositis related to cancer treatment.

Background: Oral mucositis (OM) in patients receiving cancer therapy is thus far not well managed with standard approaches. We aimed to assess the safety and effectiveness of methylene blue (MB) oral rinse for OM pain in patients receiving cancer therapy. Methods: In this randomized, single-blind phase 2 clinical trial, patients were randomized to one of four arms: MB 0.025%+conventional therapy (CTx) (n = 15), MB 0.05%+CTx (n = 14), MB 0.1%+CTx (n = 15), or CTx alone (n = 16). Intervention groups received MB oral rinse every 6 h for 2 days with outcomes measured at days 1–2; safety was evaluated up to 30 days. The primary outcome measured change in the pain numeric rating scale (0–10) from baseline to day 2. Secondary outcome measured change in oral function burden scores from baseline to day 2, World Health Organization OM grades, morphine equivalent daily doses, and adverse events. The trial was registered with ClinicalTrials.gov ID: NCT03469284. Results: Sixty patients (mean age 43, range 22–62 years) completed the study. Compared with those who received CTx alone, those who received MB had a significant reduction of pain scores at day 2 of treatment (mean ± SD); 0.025%: 5.2 ± 2.9, 0.05%: 4.5 ± 2.9, 0.1%: 5.15 ± 2.6) and reduction of oral function burden scores (0.025%: 2.5 ± 1.55, 0.05%: 2.8 ± 1.7, 0.1%: 2.9 ± 1.60). No serious adverse events were noted, but eight patients reported burning sensation of the oral cavity with the first dose, and this caused one patient to discontinue therapy. Conclusions: MB oral rinse showed significant pain reduction and improved oral functioning with minimal adverse effects. Trial registration: ClinicalTrials.gov ID: NCT03469284.