Small-Dose Trimethoprim-Sulfamethoxazole Prevents Pneumocystis Jiroveci Pneumonia in B-Cell Lymphoma Patients Receiving Chemotherapy: Analysis of a Randomized Controlled Clinical Trial

B-cell lymphoma is the most common non-Hodgkin lymphoma and is usually treated with the R-CHOP regimen. However, some patients might develop interstitial pneumonitis (IP), which has led to death in some patients. With advances in detection techniques, infections are now considered to be an important etiologic factor in IP, particularly the common opportunistic causative agent Pneumocystis jiroveci. A retrospective cohort analysis at our center has tentatively elucidated that TMP-SMX can achieve effective IP prevention. There are no prospective studies to confirm the preventive effect of TMP-SMX and its mechanism. A single-arm, single-center, randomized controlled clinical trial of TMP-SMX for the prevention of interstitial pneumonitis was conducted at our center. Prophylactic treatment with TMP-SMX in patients in the treatment group was turned on immediately after starting chemotherapy and continued until one month after the end of chemotherapy. The dose of prophylactic treatment was 0.16 g of TMP/0.8 g of SMX once daily. From April 26, 2022, to July 25, 2023, a total of 198 patients with the diagnosis of B-cell lymphoma met the criteria for enrollment and were randomly assigned to the control and treatment groups. Eleven were lost to follow-up before completing 4 courses of chemotherapy, 19 did not complete 4 courses of chemotherapy as of July 25, 2023, and 3 were excluded from the evaluation when they were switched to chemotherapy with other regimens not based on R-CHOP because of poor efficacy after 1 course of chemotherapy, among other reasons. 80 patients in the treatment group and 85 in the control group were finally included in the assessment (Figure 1, Figure 2). There were no statistical differences between patients in the control and treatment group in terms of baseline clinical characteristics such as gender, age, smoking history, lung disease, type of pathology, Ann Arbor stage, LDH level, ECOG score, IPI score, chemotherapy regimen, and group B symptoms. Observation of the primary outcome events in this study showed a significant reduction in the incidence of IP (5.0% vs 47.1%, P