Impact of lymphadenectomy extent on immunotherapy efficacy in postresectional recurred non-small cell lung cancer: a multi-institutional retrospective cohort study

Abstract

Background: Lymph node (LN) dissection is a common procedure for non-small cell lung cancer (NSCLC) to ascertain disease severity and treatment options. However, murine studies have indicated that excising tumor-draining LNs diminished immunotherapy effectiveness, though its applicability to clinical patients remains uncertain. Hence, the authors aim to illustrate the immunological implications of LN dissection by analyzing the impact of dissected LN (DLN) count on immunotherapy efficacy, and to propose a novel 'immunotherapy-driven' LN dissection strategy.

Materials and methods: The authors conducted a retrospective analysis of NSCLC patients underwent anti-PD-1 immunotherapy for recurrence between 2018 and 2020, assessing outcomes based on DLN count stratification.

Results: A total of 144 patients were included, of whom 59 had a DLN count less than or equal to 16 (median, IQR: 11, 7-13); 66 had a DLN count greater than 16 (median, IQR: 23, 19-29). With a median follow-up time of 14.3 months (95% CI: 11.0-17.6), the overall median progression-free survival (PFS) was 7.9 (95% CI: 4.1-11.7) months, 11.7 (95% CI: 7.9-15.6) months in the combination therapy subgroup, and 4.8 (95% CI: 3.1-6.4) months in the immunotherapy alone subgroup, respectively. In multivariable Cox analysis, DLN count less than or equal to 16 is associated with an improved PFS in all cohorts [primary cohort: HR=0.26 (95% CI: 0.07-0.89), P =0.03]; [validation cohort: HR=0.46 (95% CI: 0.22-0.96), P =0.04]; [entire cohort: HR=0.53 (95% CI: 0.32-0.89), P =0.02]. The prognostic benefit of DLN count less than or equal to 16 was more significant in immunotherapy alone, no adjuvant treatment, pN1, female, and squamous carcinoma subgroups. A higher level of CD8+ central memory T cell (Tcm) within LNs was associated with improved PFS (HR: 0.235, 95% CI: 0.065-0.845, P =0.027).

Conclusions: An elevated DLN count (cutoff: 16) was associated with poorer immunotherapy efficacy in recurrent NSCLC, especially pronounced in the immunotherapy alone subgroup. CD8+Tcm proportions in LNs may also impact immunotherapy efficacy. Therefore, for patients planned for adjuvant immunotherapy, a precise rather than expanded lymphadenectomy strategy to preserve immune-depending LNs is recommended.

Figure 1

Survival outcomes of patients with postresectional recurred NSCLC treated by immunotherapy. Kaplan–Meier survival curve of progression-free Survival of (A) 144 included patients; (B) 144 included patients stratified by treatment line; (C) 144 included patients stratified by anti-PD-1 regiments.

Figure 2

Impact of DLN count on PD-1 inhibitors efficacy. (A) Fitting curves to determinate the structural break point of DLN count for post-recurrent PD-1 blockade treatment. (B) Distribution of the number of DLN in the entire set. Multivariable Cox model adjusted cumulative progression-free survival in postoperative recurred NSCLC patients treated by PD-1 inhibitors stratified by DLN count of (C) Primary cohort; (D) Validation cohort; (E) Entire set. Adjusted variables included in the Cox model: pT stage, pN stage, age (cutoff: 65 years old), lines, regiments (anti-PD-1 combination therapy or anti-PD-1 immunotherapy alone), histology, adjuvant treatment (with or without), treatment cycles, and DLN count. (F) Forest plot of Cox-adjusted hazard ratio (95% CI) of DLN count>16 (with DLN count≤16 as reference) in different subgroups (age, histology, adjuvant treatment, regiment, line, metastasis stage).

Figure 3

Hierarchically clustered heatmap of (A) 64×cell-calculated and (B) 22 CIBERSORT-calculated immune cell enrichment scores in resected LN specimens from 20 patients. The vertical axis represents each LN specimen while the horizontal axis represents ×Cell- or CIBERSORT-calculated immune cell enrichment scores. A deeper color on the heatmap indicates a higher enrichment score; (C) Detailed results of the 20 patients with resected LN specimens undergone bulk RNA-seq. a, Baseline characteristic, including sex, age, histology, pathological stage, adjuvant therapy, line of treatment, and whether combined therapy or not; b, ×Cell enrichment scores of CD4+ memory T cells, CD4+Tcm, CD4+Tem, CD8+Tcm, CD8+Tem, class-switched memory B cells, and memory B cells, as well as the Cibersort enrichment scores of memory B cells, CD4+ resting memory T cells, and CD4+ activated memory T cells. c, Lymph node parameters, including. DLN group (>16, ≤16), exacted DLN number. d, Oncological outcomes, including clinical response, time of progression-free survival, and progression status. LN, lymph node; RNA-seq, RNA sequencing; Tcm, central memory T cells; Tem, effector memory T cells. The size of the bubbles, represented the enrichment scores of each memory cell type, was arranged in ascending order based on the PFS.

Figure 4

(A) Forest plot showing univariable survival analyses of LN memory cell enrichment scores. The enrichment score of each memory cell was dichotomized based on the median value. The HR (95% CI) and P value represent the HR and significance level of the survival advantage of the high- compared to the low-enrichment score group of each memory cell type. HR greater than 1 indicate a higher risk of progression. (B) Boxplot comparing LN memory cell enrichment scores between treatment response and nonresponse groups. The vertical axis represents the enrichment score calculated by ×Cell or CIBERSORT for various memory cell types. The horizontal axis shows the different memory cell types represented in the analysis. The blue boxes correspond to treatment response group, while the red boxes represent the nonresponse group. The P value for the group comparison is shown above each box. Patients who experienced a relapse within 6 months were categorized as the ‘response’ group, whereas those who did not were classified as the ‘non-response’ group. Patients with a follow-up duration of less than 6 months were excluded from the analysis. (C) Bubble plot showing the correlation between CD8+Tcm enrichment score and LN clearance, colored by RECIST1.1 response categories. Each bubble represents one patient, positioned on the plot according to their ×Cell-derived CD8+Tcm enrichment score and the number of resected LNs. The color of the bubble corresponds to the RECIST1.1 response category of the patient: purple for CR, red for PD, green for PR, and blue-gray for SD. (D) Kaplan–Meier curve plots to assess patient prognosis in CD8+Tcm high and low cohort (log-rank P value=0.0266). (E) The Sankey diagram visualizes the associations between LN CD8+ Tcm enrichment score, LN clearance, and RECIST1.1 response categories, using three vertical columns of connected ribbons. The leftmost column represents the ‘high LN CD8+Tcm’ and ‘low LN CD8+Tcm’ groups, divided by the median ×Cell enrichment score. The middle column displays the ‘DLN>16’ and ‘DLN≤16’ groups. The rightmost column illustrates the ‘CR/PR’ and ‘SD/PD’ groups, divided by RECIST1.1 criteria. The width of the ribbons corresponds to the patient count, with the ribbon color and column width indicating the degree of overlap between the groups. CR, complete response; HR, hazard ratio; LN, lymph node; Tcm, central memory T cells; Tem, effector memory T cells.