Low Molecular Weight 35 kDa Hyaluronan Fragment HA35 Effectively Controls Post-surgery and Post-radiation Pain in a Patient With Hypopharyngeal Cancer: A Case Report

Hypopharyngeal cancer, a rare form of throat cancer, is typically treated with a combination of surgery, chemotherapy, and radiation therapy. These treatments often result in severe pain and discomfort for patients, particularly after surgery and radiation therapy. Hyaluronan, a calcium channel TRPV1 blocker, can help alleviate pain. However, its clinical use is limited by its molecular weight, which affects tissue penetration. Low molecular weight hyaluronan fragments, such as HA35, have good tissue permeability and have been successfully used to treat various types of pain. We reported a case of a 50-year-old male patient with hypopharyngeal cancer, esophageal cancer, and metastases to the skull base. The patient reported nerve pain radiating to the temple due to surgical damage to the first cervical vertebra. This pain was unresponsive to five daily doses of painkillers following radiotherapy, and he required sedatives to sleep at night. He was treated with low molecular weight hyaluronan fragment HA35. The patient initially received a subcutaneous injection of 100 mg of HA35 in the shoulder and neck along with oral painkillers once daily. The timing of HA35 injections was based on the patient's self-reported numeric pain rating scale (NPRS), with an injection cycle typically lasting five to seven days per dose. After five injections, the patient experienced significant pain relief and no longer needed sedatives to sleep at night. Over a one-year follow-up period, the maintenance treatment with oral HA35 concentrate and the injection therapy following radiotherapy nearly controlled both regular pain and post-radiation pain. Moreover, the treatment substantially alleviated anxiety and fatigue while improving diet, sleep, and overall quality of life, as evidenced by improved scores on the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30). No adverse reactions were observed throughout the treatment course. These findings not only support previous studies on the efficacy of hyaluronan in mitigating radiation-induced pain but also suggest that low molecular weight 35 kDa hyaluronan fragment HA35 may offer a promising, well-tolerated strategy for long-term cancer pain management and improved patient well-being.