Hongliang Sun1, Yanyan Xu1, Queenie Chan2, and Wu Wang1
1Radiology, China-Japan Friendship Hospital, Beijing, China, 2Philips Healthcare, Hongkong, China
Synopsis
Neoadjuvant chemoradiation therapy (CRT)
followed by surgery has been established as the standard for locally advanced
rectal cancer. The treatment response after CRT is normally
evaluated by MRI. However, MRI morphology techniques suffer from limitations in the interpretation
of fibrotic scar tissue and inflammation. Several studies have
demonstrated that
sensitivity to chemoradiotherapy is related
to the oxygenation status of the tumor. It has been shown that the slight
increase in T2* signals from paramagnetic deoxyhemoglobin can be used
for reflecting the tumor oxygenation status.
Therefore, R2*(=1/T2*) might have the potential to be a predictor of prognosis
and treatment response for patients with locally advanced rectal
cancer.
Synopsis
Neoadjuvant chemoradiation therapy (CRT)
followed by surgery has been established as the standard for locally advanced
rectal cancer 1. The treatment response after CRT is normally
evaluated by MRI. However, MRI morphology techniques suffer from limitations in the interpretation
of fibrotic scar tissue and inflammation. Several studies 2, 3 have
demonstrated that
sensitivity to chemoradiotherapy is related
to the oxygenation status of the tumor. It has been shown that the slight
increase in T2* signals from paramagnetic deoxyhemoglobin can be used
for reflecting the tumor oxygenation status 4.
Therefore, R2*(=1/T2*) might have the potential to be a predictor of prognosis
and treatment response for patients with locally advanced rectal
cancer.Purpose
To evaluate the role of R2* in predict
treatment response in patients with locally advanced rectal cancer who
underwent chemoradiotherapy (CRT), with tumor regression grade (TRG) [1]
obtained by postoperative pathological results as the reference standard.Methods
Totally, 102 patients (73 men, 29 women; mean age, 58.2±11.9 years; age range, 26-79 years) with rectal cancers underwent pelvis magnetic resonance imaging (MRI) examination before
CRT. All pelvis examinations were performed in 3.0T MR unit including high
spatial resolution T2-weighted imaging (T2WI) and T2 fast field echo (T2-FFE)
sequence using five echoes (TR/TE1/DTE[ms], 644/4.0/6.9; Flip
angle, 45°; total scan duration,
5.2min). R2* was a measure of the signal loss and calculated as the slope of a
line produced by plotting the logarithm MRI signal intensity versus echo time
for the series of T2*-weighted images. Patients were categorized as responders
to CRT (TRG1-2) or non-responders (TRG3-5).The R2* values between CRT
responders and non-responders were compared by using Mann-Whitney U test.
Receiver operating characteristic(ROC) analysis was used to evaluate the
diagnostic performance of R2* in predicting the response to CRT. The area under
the ROC curve (AUC) and the optimal cut-off values were calculated, meanwhile
accuracy rate, sensitivity, specificity, positive predictive value (PPV), and
negative predictive value (NPV) was determined. Inter-observer agreement of R2*
values were evaluated using the intra-class correlation coefficient (ICC). P＜0.05 was considered to indicate a statistically
significant difference.Results
Good agreement was obtained between two
observers in terms of R2* analyses (ICC,0.8326, 95% confidence interval, 0.7618~0.8838).
There were 26 CRT responders and 76 non-responders. R2* values were
significantly higher in CRT responders (median, 31.14HZ, 1st-3rd quartiles 24.44~45.24HZ) than that in non-responders (median, 25.18HZ, 1st-3rd quartiles 21.72~30.20HZ).
According to ROC
curve, R2* values showed diagnostic significance with the AUC value of 0.702. The cutoff values for R2* were 26.92HZ (R2* values of CRT
responders was greater than this value) with accuracy rate 65.69%, sensitivity
73.08%, specificity 63.16%, PPV 40.43%, NPV 87.27% .Conclusion
R2*
derived from T2-FFE sequence demonstrated moderate value in predicting tumor
response to CRT, which seem to be more effective in rectal cancers with higher
R2* value.References
1. Letizia M, Davide I, Davide Paolo B, et al. Locally advanced rectal cancer: value of ADC mapping in prediction of tumor response to radiochemotherapy. European Journal of Radiology. 2013; 82:234-240.
2. Wright GA, Hu BS, Macovski A. Estimating oxygen saturation of blood in vivo with MR imaging at 1.5 T. J Mag Reson Imaging 1991;1:275–283.
3. Li X S, Fan H X, Fang H, et al. Value of R2* obtained from T2*-weighted imaging in predicting the prognosis of advanced cervical squamous carcinoma treated with concurrent chemoradiotherapy. Journal of Magnetic Resonance Imaging Jmri, 2015, 42(3):681-688.
4. Fyles A, Milosevic M, Hedley D, et al. Tumor hypoxia has independent predictor impact only in patients with node-negative cervix cancer. J Clin Oncol 2002;20:680–687.