BACKGROUND
cT3 substage criteria based on extramural depth of tumor invasion in rectal cancer has several limitations.
OBJECTIVE
This study proposed the distance between the deepest tumor invasion and mesorectal fascia on pre-therapy magnetic resonance imaging can distinguish cT3 patients' prognosis.
DESIGN
Cohort study.
SETTING
The study included a prospective, single-center, observational cohort and a retrospective, multicenter, independent validation cohort.
PATIENT
cT3 rectal cancer patients with negative mesorectal fascia undergoing neoadjuvant chemoradiotherapy followed by radical surgery were included in four centers of China from January 2013 to September 2014.
INTERVENTION
Baseline magnetic resonance imaging with the distance between the deepest tumor invasion and mesorectal fascia, extramural depth of tumor invasion and mesorectum thickness were measured.
MAIN OUTCOME MEASURES
The cutoff of the distance between the deepest tumor invasion and mesorectal fascia was determined by time-dependent receiver operative characteristic curves and supported by 5-year progression rate from prospective cohort, and was then validated in retrospective cohort.
RESULTS
There were 124 and 274 patients included in the prospective and independent validation cohort, respectively. The distance between the deepest tumor invasion mesorectal fascia was the only predictor for cancer-specific death (Hazard ratio: 0.1, 95% CI, 0.0-0.7); and was also a significant predictor for distant recurrence (Hazard ratio: 0.4, 95% CI, 0.2-0.9). No statistically significant difference was observed in prognosis between patient classified as T3a/b and T3c/d.
LIMITATIONS
The sample size is relatively small and the study focused on cT3 rectal cancers with a negative mesorectal fascia.
CONCLUSIONS
A cutoff of 7 mm of the distance between the deepest tumor invasion and mesorectal fascia on baseline magnetic resonance imaging can distinguish cT3 rectal cancer from different prognosis. We recommended the distance between the deepest tumor invasion and mesorectal fascia on baseline magnetic resonance imaging for local and systemic risk assessment, providing tailored schedule of neoadjuvant treatment. See Video Abstract at http://links.lww.com/DCR/B682 .