First-bite syndrome (FBS) is described as a complication of parapharyngeal space surgery and consists of short-term pain in the parotid or mandibular region at the start of each meal, usually on the first bite and improving with subsequently each bite. The pathogenesis is related to a selective sympathetic denervation of the parotid gland and its treatment involves dietary modifications, medical treatment or even surgery, all with poor results. FBS is often undervalued and misdiagnosed, yet it is a pathology that may interfere with the patient's quality of life. We report two patients who underwent major cervical oncologic surgeries. One patient was subject to extended radical neck dissection into the parapharyngeal space and the other patient ligation of the external carotid artery, which post-operatively developed into FBS unresponsive to the medical treatment instituted. During external adjuvant radiotherapy, both had an unexpected FBS improvement, remaining asymptomatic after 7 and 10 months of follow-up. In this study, we discuss why FBS is misdiagnosed in oncologic patients, the possible pathophysiological mechanisms of radiotherapy and its plausibility as a new modality of treatment in selected cases.