Elevated prevalence of nodal positivity in carcinoid tumours of the appendix smaller than 2 cm has a negative impact on overall survival.

AIM: The current standard of care for clinically node-negative carcinoid tumours of the appendix < 2.0 cm in size is appendectomy alone. The aim of this analysis was to evaluate the prevalence of pathological nodal positivity in clinically node-negative appendiceal tumour specimens < 2.0 cm and quantify the impact of occult pathological nodal positivity on overall survival following resection. METHOD: A retrospective database review of the 2019 US National Cancer Database for appendiceal cancer identified 2007 cases of clinically node-negative appendiceal carcinoid tumours based on SEER histology codes 8240, 8241, 8242, 8243, 8243, 8244, 8245, 8246 and 8249. Kaplan-Meier with log-rank testing and multivariate Cox regression analysis evaluated the impact of occult nodal positivity on overall survival following resection for clinically node-negative appendiceal carcinoma. RESULTS: The prevalence of occult nodal positivity increased from 1.9% for sub-centimetre tumours to 7% for tumours between 1.0 and 1.5 cm, 16.5% for tumours between 1.5 and 2.0 cm and to >29.5% for tumours > 2.0 cm. Rates of metastatic spread were similar for tumours < 2.0 cm but increased for larger tumours. Over two-thirds of patients received a segmental colectomy as definitive surgical therapy. After controlling for differences in cohorts, multivariate analysis showed an increased hazard ratio for mortality of 162% (HR 2.62, CI 1.884-3.541) for patients with pathological node-positive disease. CONCLUSION: Clinically node-negative carcinoid tumours of the appendix bigger than 1.5 cm have an increased rate of occult nodal spread which has a negative impact on overall survival.

Racial disparities after stoma construction in colorectal surgery.

AIM: Racial disparities are under-recognized among patients undergoing colorectal surgery. The purpose of this study was to determine the complication rates and surgical outcomes stratified by race and ethnicity among patients undergoing colorectal surgery with intestinal stoma creation. METHOD: The ACS NSQIP database from 2013 to 2016 was used. Colon, rectum and small bowel cases requiring intestinal stoma creation were selected. Both African-American and other groups of minority patients were compared with Caucasian patients using a complex multivariable analysis model. Primary outcomes of interest were complication rates, mortality and extended hospital length of stay. RESULTS: The study included 38 088 admissions. After multivariable analysis, African-American patients still had a prolonged length of hospital stay and higher complication rates. Other minorities also had a prolonged length of hospital stay and higher complication rates. CONCLUSIONS: Both African-American and other groups of minority patients requiring an ostomy suffer significantly higher postoperative complication rates and a prolonged hospital length of stay, even after comorbidity adjustment. Access to care, socioeconomic status and comorbid disease management are all important factors for minority patients who undergo colorectal surgery requiring intestinal stoma construction.

Increased food availability raises eviction rate in a cooperative breeding mammal.

In group-living mammals, the eviction of subordinate females from breeding groups by dominants may serve to reduce feeding competition or to reduce breeding competition. Here, we combined both correlational and experimental approaches to investigate whether increases in food intake by dominant females reduces their tendency to evict subordinate females in wild meerkats (Suricata suricatta). We used 20 years of long-term data to examine the association between foraging success and eviction rate, and provisioned dominant females during the second half of their pregnancy, when they most commonly evict subordinates. We show that rather than reducing the tendency for dominants to evict subordinates, foraging success of dominant females is positively associated with the probability that pregnant dominant females will evict subordinate females and that experimental feeding increased their rates of eviction. Our results suggest that it is unlikely that the eviction of subordinate females serves to reduce feeding competition and that its principal function may be to reduce reproductive competition. The increase in eviction rates following experimental feeding also suggests that rather than feeding competition, energetic constraints may normally constrain eviction rates.

Mating strategies in dominant meerkats: evidence for extra-pair paternity in relation to genetic relatedness between pair mates.

Rates of extra-pair paternity (EPP) have frequently been associated with genetic relatedness between social mates in socially monogamous birds. However, evidence is limited in mammals. Here, we investigate whether dominant females use divorce or extra-pair paternity as a strategy to avoid the negative effects of inbreeding when paired with a related male in meerkats Suricata suricatta, a species where inbreeding depression is evident for several traits. We show that dominant breeding pairs seldom divorce, but that rates of EPP are associated with genetic similarity between mates. Although extra-pair males are no more distantly related to the female than social males, they are more heterozygous. Nevertheless, extra-pair pups are not more heterozygous than within-pair pups. Whether females benefit from EPP in terms of increased fitness of the offspring, such as enhanced survival or growth, requires further investigations.

Competition, breeding success and ageing rates in female meerkats.

Competition between females is particularly intense in cooperatively breeding mammals, where one female monopolises reproduction in each group. Chronic competition often affects stress and may therefore have long-term consequences for fitness, but no studies have yet investigated whether intrasexual competition has effects of this kind and, in particular, whether it affects rates of reproductive senescence. Here, we use long-term data from a wild population of meerkats to test whether reproductive success and senescence in dominant females are affected by the degree of intrasexual competition experienced prior to dominance acquisition. Females that experienced greater competition had lower breeding success and higher rates of reproductive senescence. Furthermore, females that were evicted from the group more frequently as subordinates had lower breeding success when dominant. We conclude that the intense intrasexual competition between females in cooperatively breeding groups may carry fitness costs over a longer period than is usually recognised.