Objective:To observe the efficacy and safety of recombinant human thrombopoietin (rhTPO) in the treatment of radiation induced thrombocytopenia (RIT) .Methods:From January 2019 to March 2021, 204 cases (including 101 cases of radiotherapy alone and 103 cases of concurrent chemoradiotherapy) were collected retrospectively after radiotherapy and with decreased in blood platelet count <75×10 9/L in Jilin Cancer Hospital. These patients received rhTPO 15 000 U, once a day, subcutaneous, for at least 4 consecutive days, or met the withdrawal criteria blood platelet count ≥100×10 9/L, or the absolute value of blood platelet increase ≥50×10 9/L. The characteristics of blood platelet decline, treatment efficacy, and safety were analyzed. Results:The numbers of radiotherapy treatments with platelets lower than 75×10 9/L in the radiotherapy alone group and the concurrent chemoradiotherapy group were 19 (13, 22) and 13 (10, 17) times, respectively, indicating that patients in the concurrent chemoradiotherapy group experienced platelet decline earlier ( Z=-5.27, P<0.001), the lowest values of platelet decline in the two groups were 68 (45, 74) ×10 9/L and 62 (44, 74) ×10 9/L, respectively, with no statistically significant difference ( Z=-1.15, P=0.252). After received rhTPO treatment, the numbers of days that the two groups of patients had platelets <50×10 9/L were 7 (3, 13) d and 7 (5, 11) d, respectively, with no statistically significant difference ( Z=-1.13, P=0.281). After the patients received radiotherapy, rhTPO was started when the platelet count dropped to <75×10 9/L. The number of days required to recover to 75×10 9/L was 4 (2, 10) d in the radiotherapy alone group and 4 (2, 8) d in the concurrent chemoradiotherapy group, with no statistically significant difference ( Z=-1.07, P=0.285) ; the number of days required for platelets to recover to 100×10 9/L or for the absolute value to increase by 50×10 9/L was 8 (6, 14) d in the radiotherapy alone group and 11 (8, 16) d in the concurrent chemoradiotherapy group. The recovery time of the concurrent chemoradiotherapy group was longer than that of the radiotherapy alone group ( Z=-3.64, P<0.001). Regardless of the baseline level, there was no statistically significant difference in the number of days for platelets to recover to 75×10 9/L after rhTPO treatment between the radiotherapy alone group and the concurrent chemoradiotherapy group ( Z=-1.42, P=0.155; Z=-0.97, P=0.332). The number of days required for the two groups of patients to recover to 100×10 9/L or for the absolute value to increase by 50×10 9/L were 8 (6, 14) d and 11 (8, 16) d, respectively, with a statistically significant difference ( Z=-3.64, P<0.001). The numbers of days required for the two groups of patients with baseline platelets ≥50×10 9/L to recover to 100×10 9/L or for the absolute value to increase by 50×10 9/L were 8 (4, 12) d and 10 (8, 16) d, respectively, with a statistically significant difference ( Z=-3.12, P=0.002). However, there was no statistically significant difference in the number of days required for the two groups of patients with baseline platelets <50×10 9/L to recover to 100×10 9/L or for the absolute value to increase by 50×10 9/L ( Z=-1.88, P=0.061). The total platelet elevation rate of rhTPO within 20 days of radiotherapy treatment for both groups of patients was 93.63% (191/204), of which 95.05% (96/101) was for radiotherapy alone and 92.23% (95/103) for concurrent chemoradiotherapy, with no statistically significant difference ( χ2=0.68, P=0.410). In addition, there was no statistically significant difference in gender ( χ2=3.47, P=0.063), age ( χ2=2.79, P=0.095), TNM staging ( χ2=5.07, P=0.167), and baseline platelet count ( χ2=0.62, P=0.822) between the two groups.During the radiotherapy cycle, 27 patients (13.23%) received blood platelet infusion, and 158 patients (77.45%) completed the radiotherapy plan without interruption. No rhTPO-related adverse reactions were found. Conclusion:rhTPO in the treatment for RIT can effectively promote the recovery of blood platelet without any adverse reactions, and has good safety.