To investigate the efficacy and safety of programmed death-1 (PD-1) inhibitor targeted therapy combined with the oxaliplatin+5-fluorouracil+calcium leucovorin (mFOLFOX6) chemotherapy regimen in the preoperative neoadjuvant treatment of locally advanced middle-low rectal cancer.

Elderly patients with locally advanced middle-low rectal cancer were divided into control group and treatment group according to the treatment method. Patients in the control group received the conventional mFOLFOX6 chemotherapy regimen, with one cycle every 2 weeks for a total of 4 cycles. Patients in the treatment group received the conventional neoadjuvant chemotherapy with the mFOLFOX6 regimen combined with the PD-1 inhibitor camrelizumab injection (200 mg intravenously infused on day 1 of each cycle), with one cycle every 2 weeks for a total of 4 cycles. The surgical intervention was undertaken 4-6 weeks following completion of the chemotherapy regimen. The short-term efficacy evaluation of solid tumors, malignant tumor markers, anorectal dynamics and surgical efficiency were compared between the two groups and the safety was evaluction.

A total of 97 patients were recruited, with 54 assigned to the control group and 43 in the treatment group. After treatment, the objective response rates (ORR) were 25.93% (14 cases/54 cases) in the control group and 48.84% (21 cases/43 cases) in the treatment group; the disease control rates (DCR) were 57.41% (31 cases/54 cases) in the control group and 76.74% (33 cases/43 cases) in the treatment group, with statistically significant differences (P<0.05). After treatment, the carcinoembryonic antigen (CEA) levels in the control group and treatment group were (3.27±0.48) and (2.75±0.43) μg·L^-1, respectively; the carbohydrate antigen 199 (CA199) levels were (22.19±3.17) and (19.80±2.94) KU·L^-1, respectively. The above indicators demonstrated statistically significant differences between the treatment and control groups (all P<0.001). After treatment, the rectal resting pressure (RRP) levels in the control group and treatment group were (11.36±1.75) and (13.95±2.03) mmHg, respectively; the maximal tolerable rectalvolume (MTV) levels were (142.97±18.39) and (135.43±15.96) mL, respectively; the rectal compliance (RC) levels were (3.13±0.58) and (2.75±0.39) mL·mmHg^-1, respectively. The above indicators demonstrated statistically significant differences between the treatment and control groups (all P<0.05). The incidence of postoperative complications was 20.37% (11 cases/54 cases) in the control group and 18.60% (8 cases/43 cases) in the treatment group, with no statistically significant difference (P>0.05).

Preoperative targeted therapy with a PD-1 inhibitor combined with the mFOLFOX6 chemotherapy regimen can significantly improve the short-term efficacy of solid tumors, reduce tumor marker levels, optimize anorectal dynamics and quality of life in patients with locally advanced middle-low rectal cancer, with mild immunosuppression and good safety.