Scottsdale, AZ—Patients with oropharyngeal cancer undergoing radiation therapy experienced diminished narcotic dependency and weight loss with the use of prophylactic gabapentin, specifically given at a dose of 300 mg 3 times daily (TID), according to research presented at the 2016 Multidisciplinary Head and Neck Cancer Symposium.1
In patients with head and neck cancer, pain and weight loss are common side effects of radiation therapy, and although narcotic pain medication (NPM) is often used, these medications are not without their own side effects (eg, nausea, constipation, and respiratory depression). Furthermore, neuropathic pain often responds poorly to NPM, and requires escalating doses for pain relief.
“Single-institution retrospective reports have provided evidence that prophylactic gabapentin…may reduce the need for NPM in patients undergoing radiation therapy, however the ideal dosing schedule is unknown,” explained Tuo Dong, Howard University College of Medicine, Washington, DC, and colleagues.
Evaluating Ideal Dosages
As part of a retrospective chart review, the investigators sought to determine the ideal dose of prophylactic gabapentin needed to reduce weight loss and narcotic dependency among patients with oropharyngeal cancer undergoing radiation therapy with or without chemotherapy.
Patients with oropharyngeal cancer treated with radiotherapy in their clinic over the past 3 years were included in the analysis. Patients were stratified by use of prophylactic gabapentin. Dr Dong and colleagues then compared the quantity of NPM, time to initiation of NPM, and amount of weight loss between patients who did and did not receive prophylactic gabapentin.
The 64 patients evaluated in the study completed their prescribed radiation therapy courses, followed by ≥1 months of post-radiation therapy follow-up.
The majority of the study population were men (n = 55), and 75.6% of patients received concurrent chemotherapy. A total of 31 patients received prophylactic gabapentin (≥300 mg TID) within the first 2 weeks of radiotherapy, whereas 33 patients did not receive prophylactic gabapentin.
Less Weight Loss Seen with Prophylactic Gabapentin Use
Dr Dong and colleagues found that the patients with oropharyngeal cancer who initiated ≥300 mg TID of prophylactic gabapentin within the first 2 weeks of radiotherapy experienced less unintentional weight loss, and initiated NPM later in their radiation therapy course compared with patients who were not treated with prophylactic gabapentin. However, total NPM use was not found to be diminished in patients who received prophylactic gabapentin.
Collectively, the prophylactic gabapentin group had 47% less weight loss than the retrospective control group (4.10 kg vs 9.02 kg, P <.01). The effect of prophylactic gabapentin was not influenced by oropharyngeal subsite and p16 status, and no adverse effects were attributed to its use.
Patients who underwent upfront surgery, and patients with p16-positive disease, saw the most benefit from prophylactic gabapentin use. The surgery group given prophylactic gabapentin had 68.5% less weight loss than the untreated group (2.40 kg vs 7.63 kg, P = .02), and the p16-positive group receiving prophylactic gabapentin showed 60% less weight loss than their untreated counterparts (3.61 kg vs 9.02 kg; P = .004).
“Although this study did not elucidate a direct diminishment in overall NPM requirement with the addition of prophylactic gabapentin, this may be due to the low number of patients and the retrospective nature of our investigation,” said Dr Dong.
The researchers assert that these data support continued exploration of prophylactic gabapentin use to delay the use of—or serve as an adjunct to—standard NPM regimens in this patient population.
“Our institution intends to further explore the impact of higher prophylactic gabapentin dosing and timing and its impact on feeding tube use and quality of life metrics,” Dr Dong stated.
Reference
1. Dong T, Jones GC, Scoble D, et al. Retrospective analysis of diminished narcotic dependency and weight loss with prophylactic gabapentin use in patients undergoing radiation therapy for oropharyngeal cancer. Presented at: Multidisciplinary Head and Neck Cancer Symposium; February 18-20, 2016; Scottsdale, AZ. www.redjournal.org/article/S0360-3016(15)02052-0/pdf. Accessed April 4, 2016.