ABSTRACT
Objective: To measure the distance of the lateral, inferior, and superior microfoci from a gross tumor in a pathological speci-men and to provide scientific evidence for margin extension to form the clinical target volume (CTV) in high-dose radiotherapy for rec-tal cancer. Methods: Twenty-eight surgical specimens were collected from patients with rectal cancer who underwent total mesorectal excision (TME) in Hunan Cancer Hospital between October 2016 and April 2017. The nearest distance of the farthest peripheral micro-foci from the gross tumor was measured. The in vivo-in vitro tumor retraction factor (R1) was calculated by measuring the ratio of the tumor's perpendicular depth based on magnetic resonance imaging and immediate surgical specimens. The retraction factor (R2) in the process of pathological specimen makeup was calculated by knot labeling. The distance of microfoci extension was calculated based on that measured in pathological specimens including corrections with R1 and R2 and record as microcarcinoma extension mea-sured in vivo,MEin vivo. Results: Among the 28 pathological specimens, lateral, inferior, and superior microfoci were found in 17 (60.7%), 3 (10.7%), and 0 cases, respectively. The mean R1 was 0.913 and mean R2 was 0.803. The farthest distance measured inferiorly was 28 mm in vivo after correction. The maximum, minimum, and mean measured lateral distances were 12.03 mm, 3.03 mm, and 7.50 mm after correction, respectively. The 95% frequency value was within 10 mm. Conclusions: The lateral microfoci extension was within 10 mm for 95% of the rectal cancer patients. The margin expansion to form the CTV was suggested to be 10 mm for a late-course boost of high-dose radiotherapy for rectal cancer.
ABSTRACT
Objective:This study aimed to compare rectal cancer tumor volume parameters measured by MRI sequences (T1WI, T2WI, and DWI) and/or CT with those by pathological specimen. Methods:Twenty-two patients with rectal cancer were prospectively enrolled. MRI sequences including T1WI, T2WI, and DWI, and/or CT of the pelvis were performed before operation. Volume parameters, such as tumor length along the rectal axis, maximum tumor width perpendicular to rectal axis, and tumor actual area in that perpendicular plane, were measured on T1WI, T2WI, DWI, and CT, respectively, for each patient. The respective pathological parameters were further measured in surgical specimen after total mesorectal excision. The two kinds of parameter values measured in imaging and pathology were statistically compared and accuracy appraisal was performed. Results:The mean Lpath-L was 4.06±1.14 cm. The mean LT1-L, LT2-L, LDWI-L, and LCT-L were 3.91± 1.51, 4.62±1.41, 3.39±1.05, and 3.94±1.23 cm, respectively. Correlation coefficients were 0.688, 0.635, 0.688, and 0.720 (P<0.05). An average 6 mm overestimation was found in T2WI, and 1 to 6 mm underestimation in T1WI, DWI, and CT in length values compared with those measured in surgical specimen. The mean Lpath-W was 2.56 ±0.94 cm. The mean LT1-W, LT2-W, LDWI-W, and LCT-W were 3.62±0.99, 3.66±0.76, 3.23±0.58, and 3.64±1.04 cm, respectively. The magnitude of mean overestimation ranged from 5.1 to 11.1 mm. The Apath was 4.30 ±2.83 cm2. AT1, AT2, ADWI, and ACT were 8.98±3.90, 8.99±3.43, 8.41±3.09, and 9.63±4.40 cm2, respectively, which double overestimated the tumor area in the perpendicular rectal plane. Conclusion:The difference in longitudinal length between MRI sequences/CT and pathological specimen was in the range of?6 mm to 6 mm. The mean maximum tumor width and areas in the maximum tumor perpendicular plane were overestimated. This study indicated that gross tumor volume delineation based on CT or MRI for rectal cancer irradiation should be conservative in the axial images of rectum, and meticulous consideration is required along the rectum.