Effect of intraoperative radiation on the tensile strength of small bowel anastomoses

Radiation-induced injury on surgical margins: a clue to anastomotic leakage after rectal-cancer resection with neoadjuvant chemoradiotherapy?

Background

Few studies on anastomotic condition after rectal-cancer resection and its effect on anastomotic leakage (AL) are available up to now. This study aimed to investigate potential radiation-induced injury left on surgical margins of anterior resection after neoadjuvant chemoradiotherapy (nCRT) and its association with AL.

Methods

We retrospectively identified 161 consecutive patients who underwent anterior resection with nCRT, neoadjuvant chemotherapy without radiation (nCT) or no neoadjuvant therapy between 2014 and 2015. Tissue samples of resection margins were assessed using a specific histopathological score and microvessel density in submucosa. Propensity score matching was used to balance the baseline characteristics. Association between AL and histopathological features was analysed.

Results

AL occurred in 13 of 54 patients undergoing nCRT, 5 of 48 patients undergoing nCT and 7 of 59 patients without neoadjuvant therapy. Comparisons after matching showed median (range) histopathological scores as follows: 3 (0–8) vs 0 (0–3) vs 0 (0–2) for the proximal margin (P < 0.001); 4 (2–9) vs 0 (0–4) vs 0 (0–3) for the distal margin (P < 0.001). Correspondingly, mean (SD) microvessel densities were as follows: 21.7 (7.9) vs 27.2 (8.6) vs 27.3 (9.4) for the proximal margin (P = 0.003); 18.1 (9.3) vs 25.2 (12.9) vs 24.9 (7.4) for the distal margin (P < 0.001). Among patients undergoing nCRT, AL was associated with increased histopathological score (P = 0.003) and decreased microvessel density (P = 0.004) on the proximal margin.

Conclusions

Surgical margins of rectal-cancer resection are exposed to certain radiation-induced injury after nCRT. AL is associated with aggravated radiation damage on the proximal margin.

Sustained local application of low-dose epidermal growth factor on steroid-inhibited colonic wound healing

BACKGROUND/PURPOSE

The effects of locally administered low-dose epidermal growth factor in a steroid-inhibited wound healing were investigated in a rat model.

METHODS

Long-acting release of epidermal growth factor was enabled using microspheres embedded in gelatin sponge. Study groups consisted of 60 rats with 10 in each: colonic anastomosis only (C), plus pure gelatin sponge (CG), plus epidermal growth factor loaded sponge (CE), colonic anastomosis and steroid (S), plus gelatine sponge (SG), and plus epidermal growth factor-loaded gelatine sponge (SE) groups. Bursting pressure and wound hydroxy-proline content were measured. Bursting sites were recorded. Collagen deposits, inflammation, and foreign body reactions were evaluated.

RESULTS

Bursting pressure and hydroxy-proline contents were found lowest in the S and highest in the CE groups (P <.01). There was almost no difference between C and SE groups. Bursts were encountered in peri-anastomotic normal colon sites in the nonsteroid-treated C, CG, and CE groups. They were noted overwhelmingly at the anastomosis in steroid-inhibited S, SG, and SE groups. Histopathology results showed a standstill at the inflammatory phase of healing in S and SG groups. The best healing was observed in the CE group. Degree of collagen accumulation was well correlated with bursting pressure and hydroxy-proline content data with a negligible foreign body reaction to gelatine sponge.

CONCLUSIONS

Continuous local epidermal growth factor administration by microspheres in gelatin increases wound collagen and further enhances healing in colonic anastomoses even with steroid inhibition.

Radiation enteritis

The frequent use of radiotherapy for abdominal and pelvic malignancies results in an increased risk of radiation enteritis. An increased understanding of the tissue response and the clinical features of radiation enteritis has led to advances in the prevention and management of this condition. Importantly, improvements in the delivery of radiotherapy, including techniques to reduce the amount of exposed small intestine in the radiation field, represent a critical strategy for prevention. Data indicate that radioprotectant agents have the potential to reduce intestinal mucosal injury and may be beneficial in reducing both acute and chronic side effects of radiotherapy.

Intraoperative irradiation delays anastomotic repair in rat colon

BACKGROUND

There exists a growing interest in intraoperative radiation therapy as a treatment modality for large-bowel cancer. Since such therapy could interfere with wound repair, we investigated its effects on early healing of colonic anastomoses.

METHODS

After resection of 1 cm of colon, rats were irradiated with a single dose of 25 Gy, either to the proximal limb (P group) or to both proximal and distal limbs of the bowel (PD group) before anastomotic construction. Both groups were compared with a sham-irradiated control group. Animals were killed 3, 7, or 14 days after operation, and healing was assessed by mechanical and biochemical (collagen) parameters.

RESULTS

Three days after operation, bursting pressure was significantly lowered in the P group, whereas in the PD group both bursting pressure and breaking strength were strongly reduced. At day 7, the breaking strength was still reduced in the PD group, but not significantly so in the P group. The collagen synthetic capacity of the anastomotic segments was significantly lowered in both irradiated groups at day 3, resulting in a diminished collagen concentration in the actual wound area after 7 days. At 14 days after operation, no differences in strength were found between control and irradiated groups, while anastomotic hydroxyproline levels were significantly higher in both the P and PD groups than in the control group.

CONCLUSIONS

High-dose intraoperative radiation therapy delays the healing of colonic anastomoses; it transiently reduces strength, probably as a result of a diminished accumulation of collagen.

Effect of irradiation on healing of newly made colonic anastomoses in the rat

PURPOSE

Short-term effects of radiotherapy on the healing process of newly made colonic anastomoses are investigated by measuring the anastomotic strength in a rat model.

METHODS AND MATERIALS

Four groups of Wistar rats were used. In all groups, rats underwent a 1 cm sigmoid resection with end-to-end anastomosis. Group I served as a control group. In group II the anastomosis was irradiated after closure of the abdominal wall with a single dose of 20 Gy of 250 kV x rays. Group III was irradiated with a single dose of 20 Gy while the abdominal wall was not closed, and the surrounding tissues were carefully covered by a lead plate, simulating intra-operative radiotherapy. Group IV was treated as group III, but a larger dose of 25 Gy was applied. Animals were sacrificed 3 or 7 days after the operation. General condition of the rats was determined by observation, weight loss, serum protein and albumin at sacrifice. Anastomotic healing was evaluated by inspection, bursting pressure, hydroxyproline and protein contents of the anastomotic segment.

RESULTS

Direct postoperative externally irradiated rats (group II) showed a marked weight loss, hypoproteinaemia and hypo-albuminaemia because of involvement of small bowel in the irradiated volume. With respect to anastomotic healing there were no significant differences between control and irradiated groups.

CONCLUSION

These data suggest that the application of a single dose of irradiation (20 and 25 Gy) on colonic anastomoses given in a direct postoperative or intraoperative model has no measurable side effect on the early healing of newly made colonic anastomoses. Direct postoperative external irradiation results in unwanted side effects in the adjacent bowel.