Abnormal Neuronal Response to Rectal and Anal Stimuli in Patients Treated for Distal Rectal Cancer With High-Dose Chemoradiotherapy Followed By Watchful Waiting

BACKGROUND Watchful waiting in patients with rectal cancer with complete clinical response after chemoradiation therapy has gained increased popularity to avoid morbidity and mortality associated with surgery. Irradiation of the pelvis causes bowel dysfunction, but the effect on anorectal sensory function remains obscure in this patient category. OBJECTIVE The aim of this study was to characterize the sensory pathways of the gut-brain axis in patients with rectal cancer treated solely with chemoradiation therapy (nonconventional regime/dose) compared with healthy volunteers. DESIGN This is an explorative study. SETTINGS Sensory evaluation by rectal distension was performed and cortical evoked potentials were recorded during rapid balloon distensions of the rectum and anal canal. Latencies and amplitudes of cortical evoked potentials were compared, and the relative amplitude of 5 spectral bands from recorded cortical evoked potentials was used as an additional proxy of neuronal processing. PATIENTS Patients with rectal cancer solely with chemoradiation therapy (n = 13) a median of 3.2 years ago (range, 2.3-5.6 y) and healthy volunteers (n = 13) were included. MAIN OUTCOME MEASURES Cortical evoked potentials were measured. RESULTS Patients had 35% lower rectal capacity at a maximum tolerable volume (p = 0.007). We found no differences in rectal cortical evoked potential latencies (p = 0.09) and amplitudes (p = 0.38) between groups. However, spectral analysis of rectal cortical evoked potentials showed a decrease in θ (4-8 Hz) and an increase in β (12-32 Hz) band activity in patients (all p < 0.001). Anal cortical potentials showed an increase in α (8-12 Hz) and β and a decrease in γ (32-70 Hz) band activity (all p < 0.001) in patients compared with healthy volunteers. LIMITATIONS This is an explorative study of limited size. CONCLUSIONS Chemoradiation therapy for distal rectal cancer causes abnormal cortical processing of both anal and rectal sensory input. Such central changes may play a role in symptomatic patients, especially when refractory to local treatments. See Video Abstract at http://links.lww.com/DCR/B270. RESPUESTA NEURONAL ANORMAL A ESTIMULOS RECTALES Y ANALES, EN PACIENTES TRATADOS POR CANCER RECTAL DISTAL, CON QUIMIORRADIOTERAPIA DE DOSIS ALTA, SEGUIDA DE ESPERA VIGILANTE: La espera vigilante en pacientes de cancer rectal, con respuesta clinica completa despues de la quimiorradiacion, ha ganado una mayor popularidad en evitar la morbilidad y mortalidad asociadas con la cirugia. La irradiacion de la pelvis causa disfuncion intestinal, pero el efecto sobre la funcion sensorial ano-rectal sigue siendo no claro, en esta categoria de pacientes.El objetivo de este estudio, fue caracterizar las vias sensoriales del eje intestino-cerebro en pacientes con cancer rectal, tratados unicamente con quimiorradiacion (regimen / dosis no convencional), en comparacion con voluntarios sanos.Es un estudio exploratorio.Se realizo una evaluacion sensorial por distension rectal y se registraron los potenciales evocados corticales, durante las distensiones rapidas con balon en recto y canal anal. Se compararon las latencias y amplitudes de los potenciales evocados corticales, y la amplitud relativa de cinco bandas espectrales registradas, de potenciales evocados corticales, se usaron como proxy adicional del procesamiento neuronal.Pacientes de cancer rectal, unicamente con terapia de quimiorradiacion (n = 13) mediana de 3.2 anos (rango 2.3-5.6) y voluntarios sanos (n = 13).Potenciales evocados corticales.Pacientes tuvieron una capacidad rectal menor del 35%, al volumen maximo tolerable (p = 0.007). No encontramos diferencias en las latencias potenciales evocadas corticales rectales (p = 0.09) y amplitudes (p = 0.38) entre los grupos. Sin embargo, el analisis espectral de los potenciales evocados corticales rectales, mostro una disminucion en theta (4-8 Hz) aumento en beta (12-32 Hz), y actividad en banda en pacientes (todos p <0.001). Los potenciales evocados corticales anales mostraron un aumento en alfa (8-12 Hz) y beta, disminucion en gamma (32-70 Hz), y actividad en banda (todos p <0.001), en pacientes comparados a voluntarios sanos.Este es un estudio exploratorio de tamano limitado.La quimiorradiacion para el cancer rectal distal, ocasiona procesos corticales sensoriales anormales anales y rectales. Tales cambios centrales pueden desempenar un papel en pacientes sintomaticos, especialmente cuando son refractarios a tratamientos locales. Consulte Video Resumen en http://links.lww.com/DCR/B270.