Clinical characteristics, risk factors and outcomes of asymptomatic rectal neuroendocrine tumors

Rectal neuroendocrine tumors (NET) are often asymptomatic and frequently discovered during health examinations. However, data on the risk factors of asymptomatic rectal NETs are lacking. We investigated the risk factors, clinical characteristics and outcomes of asymptomatic rectal NETs discovered during health screening.

Asymptomatic subjects who underwent colonoscopy during routine health screening at a tertiary hospital from March 2009 to July 2014 were reviewed. Subjects with histologically confirmed rectal NETs were compared with healthy controls from the same population. Risk factors for rectal NETs were analyzed by multivariable analysis. Clinical outcomes of the resected NETs were also analyzed.

A total of 21,706 Subjects underwent screening colonoscopy during the study period. 3417 were excluded from the study, and 180 rectal NET subjects were compared with 18,109 controls. Multivariable analysis showed that a previous history of malignancy (OR 2.960, 95% CI 1.673-5.237, p < 0.001), hypertriglyceridemia (OR 1.482, 95% CI 1.046-2.100, p = 0.027), higher fasting plasma glucose levels (OR 1.008, 95% CI 1.003-1.014, p = 0.001) and higher carcinoembryonic antigen levels (OR 1.019, 95% CI 1.003-1.035, p = 0.021) were significant risk factors while older age (OR 0.964, 95% CI 0.951-0.977, p < 0.001) was a preventive factor. One hundred and sixty nine subjects had endoscopic resection, five were treated by local surgery and six by radical surgery. Complete resection was achieved in 152 subjects. There were three cases of positive lymph nodes and one metastasis. Histology revealed four lymphatic, five vascular and two cases of perineural invasion. One hundred and fifty seven subjects were followed up for at least 1 year (median 38.6 months, 12-84 months). There were no recurrences during the follow-up period.

Younger age, previous history of malignancy, higher fasting plasma glucose levels and hypertriglyceridemia are significantly associated with rectal NET risk.