Comparison between CT volume measurement and histopathological assessment of response to neoadjuvant therapy in rectal cancer.
OBJECTIVE
The aim of this study was to compare volume measurements on computed tomography (CT) images with histopathological assessments of chemoradiotherapy (CRT)-induced tumor regression in locally advanced rectal cancer (RC).


METHODS
In 25 patients (13 males, 12 females; median age, 63 years; age range, 44-79 years) with locally advanced RC treated with preoperative CRT and surgery, two radiologists measured tumor volume on CT images before and after CRT. CT-based tumor volumetry and the modified response evaluation criteria in solid tumors (mRECISTs) were compared with T and N downstaging after CRT, and with the tumor regression grade (TRG).


RESULTS
Tumor volumes were significantly smaller on CT images after CRT. The tumors regressed in 52% (13/25), 36% (9/25) and 40% (10/25) of patients, based on T downstaging, TRG and mRECIST findings, respectively. In terms of T downstaging, the pre- and post-CRT tumor volumes of responders and non-responders to the treatment differed statistically, while their tumor volume reduction rates and volume reductions according to the 65% mRECIST threshold did not. In terms of N downstaging and TRG, the differences between the responders' and the non-responders' pre- and post-CRT tumor volumes, tumor volume reduction rates, and mRECIST thresholds were never statistically significant.


CONCLUSIONS
Measuring tumor size on CT images is of limited value in predicting the histopathological response to preoperative CRT in RC patients, so it may be unwise to select surgical treatment strategies based on CT volumetry.
Veneto Institute of Oncology IOV-IRCCS, via Gattamelata 64, 35128 Padua, Italy. fabio.pomerri@unipd.it
Fabio
F
Pomerri
Salvatore
S
Pucciarelli
Gisella
G
Gennaro
Isacco
I
Maretto
Donato
D
Nitti
Pier Carlo
PC
Muzzio
D000328:Adult; D000368:Aged; D001707:Biopsy, Needle; D059186:Chemoradiotherapy, Adjuvant; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D047368:Tumor Burden