# The effect of neoadjuvant radiotherapy on immune cell infiltrates in myxofibrosarcoma

## TL;DR

Neoadjuvant radiotherapy in myxofibrosarcoma reduces T cell infiltration but increases natural killer cells, suggesting a shift in the tumor's immune environment.

## Contribution

This study is the first to investigate the impact of neoadjuvant radiotherapy on the immune microenvironment of myxofibrosarcoma.

## Key findings

- Neoadjuvant radiotherapy reduces cytotoxic and helper T cell infiltration in myxofibrosarcoma.
- Natural killer cell infiltration increases after neoadjuvant radiotherapy in myxofibrosarcoma.
- There is significant interpatient variability in immune cell infiltration both before and after treatment.

## Abstract

Myxofibrosarcoma (MFS) is a subtype of soft-tissue sarcoma for which local treatment includes neoadjuvant radiotherapy (nRT) followed by surgery. The impact of nRT on the MFS tumor immune microenvironment remains unexplored.

Paired pre-nRT biopsy and post-nRT surgery samples from 31 MFS patients were retrospectively collected. The intratumoral density of T cells, cytotoxic T cells, regulatory T cells, helper T cells, B cells and natural killer (NK) cells and expression of programmed death-ligand 1 were quantified using multiplex immunohistochemistry (mIHC). mIHC marker densities were compared between pre- and post-nRT samples, and their associations with clinicopathological characteristics and patient outcomes were assessed.

There was substantial interpatient heterogeneity in mIHC marker densities, both pre- and post-nRT. A significant reduction in cytotoxic T cell {205 [interquartile range (IQR) 674] pre-nRT versus 58 (IQR 205) post-nRT, P = 0.030} and helper T cell [220 (IQR 343) pre-nRT versus 74 (IQR 110) post-nRT, P = 0.011] densities, alongside an increase in NK cell [2 (IQR 8) pre-nRT versus 7 (IQR 16) post-nRT, P = 0.050] infiltration, was observed following nRT. There were no statistically significant associations between mIHC marker densities measured before or after nRT, or their changes over time, and patient outcomes.

Conventional nRT is associated with reduced cytotoxic and helper T cell infiltration and increased presence of NK cells in MFS. These results suggest that conventional nRT reduces inflammatory aspects of MFS tumors.

•Comparison of paired pre- and post-nRT MFS samples revealed nRT-induced changes in intratumoral lymphocyte densities.•Both pre- and post-nRT MFS samples showed strong inter‑patient heterogeneity in intratumoral lymphocyte infiltration.•Conventional nRT was associated with reduced intratumoral cytotoxic T-cell and helper T-cell densities in MFS.•MFS samples obtained after nRT harbored increased intratumoral NK cell densities.•An increase in intratumoral T-cell densities after nRT was associated with a trend toward improved outcomes in MFS.

Comparison of paired pre- and post-nRT MFS samples revealed nRT-induced changes in intratumoral lymphocyte densities.

Both pre- and post-nRT MFS samples showed strong inter‑patient heterogeneity in intratumoral lymphocyte infiltration.

Conventional nRT was associated with reduced intratumoral cytotoxic T-cell and helper T-cell densities in MFS.

MFS samples obtained after nRT harbored increased intratumoral NK cell densities.

An increase in intratumoral T-cell densities after nRT was associated with a trend toward improved outcomes in MFS.