Prevention of postoperative complications in colorectal cancer
Worldwide, colorectal cancer (CRC) is the third most frequent cancer in men, the second most common in women and the fourth leading cause of cancer-related death. Surgery is one therapeutic option, but it is related to a very high rate of complications (50% of them infections, in the abdominal and pelvic cavity). Such complications lengthen hospital admission times and increase the cost of treatment, while also jeopardizing its success. Possible causes of infectious complications include incomplete preoperative intestinal lavage (residual faeces) and incisions to the colon during the operation, causing postoperative anastomotic leak, both of which increase the chances of bacterial contamination in the peritoneal cavity and surgical wound, given the weakness of the immune system due to the cancer and surgical stress. These latter factors are considered the most significant.
The nutritional and pharmacological effects of the omega-3 polyunsaturated fatty acids (omega-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) mean they are currently included (in fish oil) in enteral and parenteral nutrition for patients in intensive care units and who have undergone surgery. Various meta-analyses covering all kinds of surgery patients indicate that omega-3 PUFAs improve both the infection rate and hospitalisation times, while studies on animal models and observational studies of omega-3 PUFA-enriched immune nutrition have demonstrated their anti-platelet, anti-inflammatory, anti-angiogenic and anti-CRC effects.
A meta-analysis of controlled, randomised studies on the short-term clinical efficacy of immunonutrition with omega-3 PUFA in colorectal cancer published in Pubmed, Embase and the Cochrane Library up to March 2016 was carried out to assess the clinical efficacy of omega-3 PUFA.
The results showed that, compared to control patients, omega-3 PUFA-enriched enteral and parenteral nutrition reduced postoperative infectious complications (15.6% v. 24.8%, p=0.004), serum tumour necrosis factor-alpha (TNFα, p=0.01), serum interleukin-6 (IL-6, p=0.02), both inflammatory cytokines and post-surgery hospitalisation times (p=0.01).
With regard to the immunonutrition administration period, a distinction is made between the perioperative (9-14 days) and pre- or postoperative (5-7 days) periods, resulting in significant differences in the shorter period. Some authors defend the longer period as optimum, arguing that patients face surgical stress with a better omega-3 PUFA status and early postoperative nutrition is an important factor in recovering intestinal function and physiological condition. Indeed, another recent meta-analysis concluded that perioperative immunonutrition is better than pre- or postoperative nutrition in preventing postoperative infectious complications. The results of this study might be due to the influence of the perioperative sub-group sample size on the power of the test, the fact that the group included only patients who received oral enteral nutrition (which might not be sufficiently assimilated), while the postoperative group included patients that received intravenous parenteral nutrition, or due to different doses and formulations of the omega-3 PUFA.