Effect of Intraperitoneal Chemotherapy with Regorafenib on IL-6 and TNF-α Levels and Peritoneal Cytology: Experimental Study in Rats with Colorectal Peritoneal Carcinomatosis

Abstract

Cytoreductive surgery (CRS), combined with hyperthermic intraperitoneal chemotherapy, has significantly improved survival outcomes in patients with peritoneal carcinomatosis from colorectal cancer (CRC). Regorafenib is an oral agent administered in patients with refractory metastatic CRC. Our aim was to investigate the outcomes of intraperitoneal administration of regorafenib for intraperitoneal chemotherapy (IPEC) or/and CRS in a rat model of colorectal peritoneal metastases regarding immunology and peritoneal cytology. A total of 24 rats were included. Twenty-eight days after carcinogenesis induction, rats were randomized into following groups: group A: control group; group B: CRS only; group C: IPEC only; and group D: CRS + IPEC. On day 56 after carcinogenesis, euthanasia and laparotomy were performed. Serum levels of interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α) as well as peritoneal cytology were investigated. Groups B and D had statistically significant lower mean levels of IL-6 and TNF-α compared to groups A and C, but there was no significant difference between them. Both B and D groups presented a statistically significant difference regarding the rate of negative peritoneal cytology, when compared to the control group, but not to group C. In conclusion, regorafenib-based IPEC, combined with CRS, may constitute a promising tool against peritoneal carcinomatosis by altering the tumor microenvironment.

Keywords: colorectal cancer; cytoreductive surgery; intraperitoneal chemotherapy; intraperitoneal injection; peritoneal carcinomatosis; regorafenib.

Figure 1

An overview of the experimental design. This figure was created with BioRender.com.

Figure 2

Serum IL-6 levels at T2 (Day 56) (asterisks indicate significant differences). Carcinogenesis induction was performed at T0 (Day 0). After 28 days (T1-Day 28), rats were allocated randomly into 4 groups (group A: control group; group B: CRS only; group C: IPEC only; group D: CRS + IPEC). Regorafenib (10 mg/kg) was used as an IPEC agent. Fifty-six days after carcinogenesis, blood samples were collected for IL-6 level measurement. The confidence interval was set at 95%, which means that the differences between the groups were considered statistically significant when p < 0.05. * p < 0.05.

Figure 3

Serum TNF-a levels at T2 (Day 56) (asterisks indicate significant differences). Carcinogenesis induction was performed at T0 (Day 0). After 28 days (T1-Day 28), rats were allocated randomly into 4 groups (group A: control group; group B: CRS only; group C: IPEC only; group D: CRS + IPEC). Regorafenib (10 mg/kg) was used as an IPEC agent. Fifty-six days after carcinogenesis, blood samples were collected for TNF-a level measurement. The confidence interval was set at 95%, which means that the differences between the groups were considered statistically significant when p < 0.05. * p < 0.05.

Figure 4

Peritoneal cytology. The malignant cells are arranged in clusters with overlapping nuclei.

Figure 5

Peritoneal cytology results at T2 (Day 56) (asterisks indicate significant differences). Carcinogenesis induction was performed at T0 (Day 0). After 28 days (T1-Day 28), rats were allocated randomly into 4 groups (group A: control group; group B: CRS only; group C: IPEC only; group D: CRS + IPEC). Regorafenib (10 mg/kg) was used as an IPEC agent. Fifty-six days after carcinogenesis, euthanasia and midline laparotomy were performed. A peritoneal cytology sample was collected with a suction device from the peritoneal space. All ascetic specimens were prepared using the ThinPrep liquid-based cytology preparation system (Cytyc Co., Boxborough, MA, USA). The confidence interval was set at 95%, which means that the differences between the groups were considered statistically significant when p < 0.05. * p < 0.05.