AbstractCONTEXT: Existing studies on breakthrough pain (BP) have reported different prevalence rates because of different settings, populations, and assessment methods. These studies have used cross-sectional designs, and the relationship of BP with analgesic treatment has not been evaluated.OBJECTIVES: The aim of this study was to longitudinally assess BP in cancer patients admitted to oncology units.METHODS: A consecutive sample of patients admitted to oncology centers was selected. At admission (T0), three months after admission (T3), and six months after admission (T6), data on background pain and BP were recorded. BP was assessed in terms of its intensity, duration, number of episodes, onset with movement, spontaneous relief after stopping activity, limitation of physical activity, and effectiveness of analgesics.RESULTS: Three hundred two patients completed the study. At T0, T3, and T6, 39%, 38%, and 33% patients, respectively, had continuous pain (P=0.294). Pain intensity significantly decreased (P=0.004 and 0.027 at T3 and T6, respectively). Most patients had BP at T0 (87.1%), T3 (80.9%), and T6 (73.2%), and there was a significant decrease in the prevalence of BP over time (P=0.016). Of 149 patients with BP, pain on movement was recorded in 43.6%, 43.4%, and 32.4% at T0, T3, and T6, respectively (P=0.228). Pain spontaneously decreased or ceased when stopping physical activity in 66%, 56%, and 62% at T0, T3, and T6, respectively (P=0.537). Pain on movement strongly limited physical activity in most patients.CONCLUSION: These data expand current information about BP and underline the need for a longitudinal assessment of a phenomenon that is invariably dependent on stage of disease, patient, and therapeutic factors.