Biological and clinical review of IORT-induced wound fluid in breast cancer patients

Abstract

Intraoperative radiotherapy (IORT) has become a growing therapy for early-stage breast cancer (BC). Some studies claim that wound fluid (seroma), a common consequence of surgical excision in the tumor cavity, can reflect the effects of IORT on cancer inhibition. However, further research by our team and other researchers, such as analysis of seroma composition, affected cell lines, and primary tissues in two-dimensional (2D) and three-dimensional (3D) culture systems, clarified that seroma could not address the questions about IORT effectiveness in the surgical site. In this review, we mention the factors involved in tumor recurrence, direct or indirect effects of IORT on BC, and all the studies associated with BC seroma to attain more information about the impact of IORT-induced seroma to make a better decision to remove or remain after surgery and IORT. Finally, we suggest that seroma studies cannot decipher the mechanisms underlying the effectiveness of IORT in BC patients. The question of whether IORT-seroma has a beneficial effect can only be answered in a trial with a clinical endpoint, which is not even ongoing.

Keywords: IORT; breast cancer; personalized medicine; seroma; tumor microenvironment.

Figure 1

Factors involved in breast cancer recurrence. The left side of the picture shows the histopathologic types and molecular subtypes of the tumors in the recurrence of the disease. The right side of the picture shows the role of tumor heterogeneity, microenvironment, and immune system in breast cancer recurrence. Several clonal tumors containing CSCs are seen in tumor bulk and CSCs can affect the heterogenic migration of various clones in a single tumor. CSC also promote the EMT process and cause metastasis of BC tumor cell to the cervix, brain, liver, lung, and bone marrow. Cancer cells can recruit the immune system to progress tumor or even metastasis. Specific immune cells, including macrophages, lymphocytes, NK cells, dendritic cells (DCs), and neutrophils, are abundant and actively involved in the progression or suppression of cancer dissemination at the site of metastasis. Indeed, cancer cells can indirectly modulate and suppress the immune response (30, 32). CAFs promote tumor progression by initiating extracellular matrix remodeling through cytokine secretion. CAFs could suppress or avoid the immune response by promoting the recruitment of regulatory T cells (Treg), which is mediated by inflammation, or stopping the proliferation of T helper cells and killer T cells (28, 29). Work as tumor-modifying cells that may induce a change in cancer cell phenotype. CAAs produce hormones, growth factors, and cytokines. TAMs are the predominant immune cell types with immunosuppressive M2 polarized phenotypes that secrete tumor cytokines. Exosomes are essential in impairing both the adaptive and innate immune systems. It was shown that exosomal PDL1 derived from BC promotes and protects tumor growth by attaching to the PD-1 receptor of the CD8 T cells; thus, their adaptive killing activities are inhibited. Moreover, T-cells inhibit exosome secretion significantly through their anti-tumor immunity. In addition, uncontrolled cell proliferation induced by exosomes leads to inadequate nutrient and oxygen flow that derives the tumor microenvironment from becoming hypoxic. This process further triggers Epithelial-to-Mesenchymal Transition (EMT) and also promotes a more invasive phenotype. Further explanations are available in the text. TAN, tumor-associated neutrophil; TAM, tumor-associated macrophage; CAA, cancer-associated adipocyte; CAF, cancer-associated fibroblast; ECM, extracellular matrix; EMT, epithelial to mesenchymal transition; TNBC, triple-negative breast cancer; CSC, cancer stem cell. The figure was created using Biorender (https://biorender.com).

Figure 2

Direct and indirect effects of IORT on cancer inhibition and recurrence. After the breast-conserving surgery, molecular and probably remained cancer cells in the tumor cavity will be affected by IORT. Briefly, irradiation on the tumor cavity impairs DNA repair mechanisms, induces cell death, inhibits proliferation and metastasis, alters gene and protein profiles, impairs the cell-cell junction, and induces ECM fibrosis. In indirect effects of IORT, inactivated remained tumor cells release exosomes and tumor antigens which move and deliver to lymphatic vessels through the circulating system and APCs, respectively. IORT-induced tumor antigens and exosomes effects non-irradiated tumor cells in the body via a mechanism named “abscopal effect” (33). The figure was created using Biorender (https://biorender.com).

Figure 3

Graphical abstract for performed studies in breast surgery IORT- and non-IORT-seroma and their effects on breast cancer.

Figure 4

The studies related to seroma composition. Red boxes show the level of protein expression in seroma without considering radiotherapy. Green boxes show protein expression levels in an IORT-affected seroma compared to non-IORT-affected seroma.

Figure 5

The studies related to the effects of seroma on BC cell lines. The right part of the circle shows the results from the effects of breast cancer seroma on breast cancer cell lines. The left part of the circle shows the results of the effects of IORT-treated and non-IORT-treated breast cancer seroma on breast cancer cell lines.

Figure 6

The studies related to the effects of seroma on primary BC cells. (A) Effects of drugs on seroma-treated human-derived breast cancer cells in 2D cell culture system. (B) Effects of IORT-treated and non-IORT-treated seroma on human-derived breast tumor spheroids in 3D microfluidic chips (visual evaluation of proliferation and migration). (C) Effects of IORT-treated and non-IORT-treated seroma on human-derived breast tumor spheroids in 3D microfluidic chips (visual and molecular evaluation of proliferation, apoptosis, migration, and heterogeneity).