Objective To explore the short- and long-term therapeutic efficacy and adverse reactions caused by various radiotherapy doses in radical synchronous radiotherapy and chemotherapy of thoracic esophageal squamous cell carcinoma to find the optimal radiotherapy dose pattern for esophageal cancer chemoradiotherapy.

Methods A retrospective analysis was conducted on the clinical data of 158 patients with thoracic esophageal squamous cell carcinoma who received radical synchronous radiotherapy and chemotherapy from January 2014 to June 2017 in the Xinjiang Bazhou People's Hospital and the Fourth Hospital of Hebei Medical University. The patients comprised 95 males and 63 females, aged (57.2±7.4) years, and were divided into high- (55.0 to 60.0 Gy) with 75 cases and low-dose (50.4 to 55.0 Gy) with 83 cases radiotherapy groups based on various radiotherapy doses. The patients were matched with the closest propensity scores in the two groups via a 1∶1 propensity score matching (PSM) method. Comparisons were conducted on the differences in various clinical data before and after matching, changes in the expression levels of serum T lymphocyte subsets before and after treatment, short-term efficacy, and the incidence of adverse reactions. Between-groups comparisons were performed using two independent-sample t-tests and χ² tests. Kaplan-Meier survival analysis was conducted to compare the progression-free survival rate and overall survival rate of the matched groups after radical synchronous radiotherapy and chemotherapy.

Results The age, maximum tumor diameter, T stage, and N stage of the two groups before PSM method matching were compared, and the differences showed statistical significance (t=1.589, 4.322, χ²=4.789, 5.112; all P<0.05). A total of 46 pairs of patients were successfully matched in the two groups. After PSM method matching, the clinical data between the two groups of patients were compared, and the results indicated no statistically significant differences (t=0.196−0.624, χ²=0.386−0.517; all P>0.05). The high-dose radiotherapy group exhibited a significantly higher objective response rate than the low-dose radiotherapy group (65.2%(30/46) vs. 32.6%(15/46)), and the difference was statistically significant (χ²=5.144, P=0.032). After treatment, the low-dose radiotherapy group showed higher serum CD4⁺ and ratio of CD4⁺/CD8⁺ levels than the high-dose radiotherapy group and a lower serum CD8⁺ level. However, these differences were not statistically significant (t=1.145−1.389; all P>0.05). The low-dose radiotherapy group attained significantly lower incidences of grade 3−4 radiation esophagitis, radiation pneumonitis, bone marrow suppression, and gastrointestinal reactions than the high-dose radiotherapy group (15.2%(7/46) vs. 56.5%(26/46), 26.1%(12/46) vs. 60.9%(28/46), 30.4%(14/46) vs. 65.2%(30/46), 34.8%(16/46) vs. 73.9%(34/46)), the differences were statistically significant (χ²=4.356−5.923, all P<0.05). The high-dose radiotherapy group presented a significantly higher 5-year progression-free survival rate and overall survival rate after radical synchronous radiotherapy and chemotherapy compared with the low-dose radiotherapy group (37.0%(17/46) vs. 17.4%(8/46), 73.9%(34/46) vs. 52.2%(24/46)), and the differences were statistically significant (χ²=4.449, 4.665; both P<0.05).

Conclusions Compared with the low dose radiotherapy pattern of 50.4 Gy, high-dose radiotherapy can considerably improve the local tumor control rate in patients with thoracic esophageal squamous cell carcinoma undergoing radical synchronous radiotherapy and chemotherapy and improve the progression-free rate and overall survival rate. However, such procedure can also increase treatment-related adverse reactions to some extent.