[Clinicopathological and prognostic features of young onset patients with middle-low rectal cancer received neoadjuvant chemoradiotherapy]. Objective: To explore the clinicopathological and prognostic features of young onset patients with middle-low rectal cancer who received neoadjuvant chemoradiotherapy (NCRT).  Methods: After NCRT, a total of 441 patients with primary middle-low rectal cancer treated with radical surgery at the Cancer Hospital, Chinese Academy of Medical Sciences (CHCAMS) from January 2004 to December 2016 were included.  According to the age of disease onset, the patients were divided into the young group (51cases) and the middle-old group (390 cases), and the clinicopathological characteristics and survival of these patients were analyzed.  Results: In the young group, 68.6% of patients received radical surgery within 7 weeks after NCRT, which was higher than 52.8% in the middle-old group (P=0.047).  The stage ypN+ in the young group was 51.0%, higher than 34.1% in the middle-old group (P=0.047), The incidence of disease progression in the young group was 39.2%, higher than 25.1% in the middle-old group (P=0.049).  The incidence of distant metastasis in the young group was 35.3%, higher than 21.5% in the middle-old group(P=0.044).  Most cases of disease progression occurred in the first 3 years after surgery for the young group, especially in the second year after surgery, the incidence of disease progression in the young group was 55.0%, higher than 26.5% in middle-old group (P=0.025).  The 3-year and 5-year disease-free survival (DFS) rates for the young group were 63.7% and 58.2%, lower than 81.0% and 74.3% in the middle-old group (P=0.016), respectively.  The 3-year and 5-year overall survival in the middle-old group (OS) rates for the young group were 85.4% and 69.2%, lower than 93.6% and 84.1% in the middle-old group (P=0.033), respectively.  The multivariate analysis showed that, response of primary tumor (HR=4.804, 95% CI: 1.360-16.973) and total number of dissected lymph nodes (HR=4.336, 95% CI: 1.739-10.809) in the young group were independent prognostic factors related to DFS.  The total dissected number of lymph nodes(HR=3.295, 95% CI: 1.076-10.091)was an independent prognostic factor related to OS.  In the middle-old group, response of primary tumor (HR=2.626, 95% CI: 1.354-5.091), ypTNM stage (ypTNM Ⅲ: HR=5.837, 95% CI: 2.968-11.479) and tumor location distance from the anal verge (HR=0.500, 95% CI: 0.308-0.812) were independent prognostic factors related to DFS.  Lymphovascular invasion (HR=0.500, 95% CI: 0.308-0.812) and ypTNM stage (ypTNM Ⅲ: HR=16.322, 95% CI: 5.049-52.771) were independent prognostic factors related to OS.  Conclusions: Young onset rectal cancer patients are associated with shorter operation time interval, advanced pathological stage and poorer prognosis.  More intensive adjuvant treatment and post-treatment surveillance should be conducted to young onset rectal cancer with NCRT.
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