Effect of gabapentin on anxiety among 306 breast cancer patients: A URCC CCOP study

Background: Anxiety is prevalent among 18%-77% of cancer patients and is associated with increased insomnia, depression, fatigue and reduced quality of life. In a previous study, we found that gabapentin is effective in reducing hot flashes among cancer patients. Gabapentin is used for treatment of anxiety disorders but there is little scientific evidence supporting its use. The aim of this secondary data analysis is to examine the effect of gabapentin on anxiety. Methods: 420 breast cancer patients experiencing ≥ 2 hot flashes a day were randomized to placebo, gabapentin 300 mg/day, or gabapentin 900 mg/day for 8 weeks (wks). Anxiety was measured by the State-Trait Anxiety Inventory (STAI) at baseline, 4 and 8 wks. Results: At 4 wks, patients (n = 334) receiving gabapentin 300mg reported a reduction in anxiety (change score [CS] = -2.08, standard error [SE] = 0.89) while patients receiving gabapentin 900mg and placebo reported an increase in anxiety (900 mg CS = +0.32, SE = 0.87, placebo CS = +1.01, SE = 0.76). At 8 wks, patients (n = 306) receiving gabapentin 300mg reported a further reduction in anxiety (CS = -2.65, SE = 0.86) while patients receiving gabapentin 900mg and placebo continued to reported increases in anxiety (900 mg CS = +0.16, SE = 1.03, placebo CS = +1.89, SE = 0.97). ANCOVAs controlling for baseline anxiety revealed significantly lower anxiety at 4 and 8 wks among patients receiving gabapentin 300 mg compared to patients receiving placebo (all p \u3c 0.05) with no significant differences between patients receiving gabapentin 900 mg and those receiving placebo. ANCOVAs also showed a significant baseline by treatment interaction at 4 wks (p \u3c 0.05); where patients with higher baseline anxiety reported the greatest reductions in anxiety, but this interaction effect was not present at 8 wks. Conclusions: Gabapentin administered at 300 mg/day is useful in reducing anxiety experienced by breast cancer patients and may be particularly useful for patients experiencing high levels of anxiety short-term. The 300 mg dose may be more effective compared to the 900 mg dose due to an anxiety receptor-specific physiological effect and/or the combination of fewer drug-related toxicities resulting from the lower dose. Funding: U10CA37420 and K07CA132916. No significant financial relationships to disclose