576P - Prognostic values of a modified diagnostic biopsy-adapted immunoscore based on double immunohistochemical staining in patients with locally advanced rectal cancer

Background

Tumor immune contexture plays a crucial role in the outcome of cancer patients. The aim of this study was to evaluate the prognostic value of the modified diagnostic biopsy-adapted immunoscore (mIS_b) for patients with locally advanced rectal cancer (LARC).

Methods

We included 181 LARC patients from a single sub-center of a prospective study (NCT02533271), with 151 (83.4%) receiving surgical treatment and 30 (16.6%) following a watch-and-wait (W&W) strategy. Tumor biopsy tissues were stained using dual immunohistochemistry for CD8+ and CD3+ T cell densities, and the CD8/CD3 ratio was calculated. mISb was developed using mean percentile values of CD8+ T cell density and CD8/CD3 ratio, and patients were classified into low (0%-25%), intermediate (>25%-70%), and high (>70%-100%) mIS_b groups. Spearman correlation analysis was performed. Kaplan-Meier survival analysis, multivariate Cox regression models were used to assess the prognostic value of mIS_b for disease-free survival (DFS), and the role of mIS_b in the W&W strategy was further investigated.

Results

A strong correlation was found between CD8+ and CD3+ T cell densities (R=0.86, P<0.001), and a weaker correlation with the CD8/CD3 ratio (R=0.45). In the low, intermediate, and high mIS_b groups, there were 35 (23.2%), 84 (55.6%), and 32 (21.2%) patients, respectively. The respective 3-year DFS rates for these groups were 59.0%, 69.5%, and 80.1% (P=0.01). Multivariate analysis in surgically treated patients revealed mIS_b as an independent prognostic factor for DFS (intermediate vs. high: HR=2.38, 95% CI: 0.92-6.16, P=0.08; low vs. high: HR=3.69, 95% CI: 1.35-10.07, P=0.01). Among W&W patients, 6 (37.5%) in the mIS_b≤50% group experienced local-region or distant metastases, while only 1 (7.1%) in the mIS_b>50% group had local-region recurrence.

Conclusions

mIS_b, as a potentially valuable prognostic indicator, demonstrates significant importance in assessing the prognosis of LARC patients. Future research is needed to further investigate the clinical application of mIS_b in rectal cancer prognosis, particularly in the context of the W&W strategy.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.