PURPOSE/OBJECTIVE(S): Patients who receive radiotherapy (RT) for head and neck cancer (HNC) are at risk for late radiation toxicity, recurrence, and subsequent neoplasms. Ongoing monitoring by a radiation oncologist during the survivorship period is important for detection of adverse outcomes and to guide early intervention. The purpose of this study was to identify patient level factors associated with HNC survivors becoming lost to radiation oncology follow-up care. MATERIALS/METHODS: This cross-sectional study included all surviving patients who received RT for HNC at a single comprehensive cancer center in Alabama between 2001-2018. Death records were identified using a combination of medical records and LexisNexis Accurint. Patients who had not been evaluated in the radiation oncology clinic for > 2 years were considered as lost to follow-up care. Patient level factors considered for association with becoming lost to follow-up included age (older vs. young than 65 years), distance from the clinic (more vs. less than 100 miles), median income of the zip code of residence (above vs. below median), sex, race (white vs. non-white) and time since completion of RT (more vs. fewer than 5 years). Between group differences in frequencies were assessed using the chi-square test. A classification tree was created to classify participants according to the risk of becoming lost to follow-up, with terminal nodes required to contain at least 50 patients. RESULTS: Of the 737 patients who met the inclusion criteria, 391 (53.1%) had not been evaluated by a radiation oncologist for > 2 years. When considered individually, becoming lost to follow-up was statistically more common among patients who were > 5 years from RT (61.4% vs. 39.1%, P < 0.001), below the median income for the state of Alabama (55.8% vs. 47%, P = 0.025), and were unmarried (61.7% vs. 46.4%, P < 0.001). The first level split of the decision tree was by time from completion of RT. For patients within 5 years of completing RT, unmarried patients were more likely to be lost to follow-up (67.9% vs. 32.1%). For patients more than 5 years from completion of RT, the group consisting of both unmarried patients and married patients living > 100 miles from the clinic were more likely to be lost to follow-up (69% vs. 31%). CONCLUSION: This study identified time from RT, marital status, income level, and travel distance as factors associated with becoming lost to radiation oncology follow-up at an academic center in the Deep South. The decision tree supports the hypothesis that distance to the clinic may become more meaningful later in the survivorship period. Identifying factors associated with becoming lost to specialty care after cancer treatment is important for developing and targeting social support interventions for cancer survivors, particularly those with HNC who are disproportionately affected by socioeconomic disparities.