Objective To investigate the changes in peripheral blood immune cells before and after the onset of septic shock in patients with malignant tumors, and to analyze the relationship between these immune cells and patient prognosis.

Methods A retrospective study was conducted, enrolling perioperative tumor patients who were transferred to the intensive care unit (ICU) due to septic shock at Shanxi Provincial Cancer Hospital between October 2018 and December 2019.Changes in lymphocyte counts and subsets were compared before and after septic shock (measured prior to septic shock onset and within 72 hours after onset).A multivariate Logistic regression model was used to analyze the relationship between these immune indicators and the 28-day mortality risk in tumor patients following septic shock.

Results A total of 47 tumor patients transferred to the ICU due to septic shock were included.There were 32 males and 15 females, with a mean age of (63.9±11.2) years.Gastrointestinal tumors were the most common tumor type (76.60%, 36/47), and abdominal/pelvic infection (65.96%, 31/47) was the primary source of infection.Within 28 days after ICU transfer, 12 patients died and 35 survived. Compared to pre-septic shock levels, lymphocyte counts significantly decreased after septic shock530(300, 830) cells/μL vs. 1530(1020, 2020) cells/μL, P < 0.001.Lymphocyte subset analysis revealed that, compared to pre-septic shock levels, counts of all other immune cells significantly decreased after septic shock except for total B-cell count (all P < 0.05).Between-group comparisons demonstrated no significant differences in natural killer T-cell or natural killer cell counts between non-survivors and survivors (all P>0.05);however, the remaining immune cell counts were significantly lower in non-survivors compared with survivors (all P < 0.05).Multivariate Logistic regression analysisadjusted for age, lactate level, and acute physiology and chronic health evaluation Ⅱ(APACHE Ⅱ) scoreshowed that regulatory T cell counts after septic shock were significantly negatively correlated with 28-day all-cause mortality (OR=0.938, 95% CI: 0.886-0.993, P=0.028).

Conclusions Perioperative tumor patients experience acute depletion of peripheral blood lymphocyte subsets following septic shock.Among various immune indicators, regulatory T cell count serves as an independent predictor of short-term mortality risk.Evaluating baseline immune function in such patients may help optimize treatment strategies and improve overall prognosis.