Diffusion-weighted MR imaging: pretreatment prediction of response to neoadjuvant chemotherapy in patients with breast cancer.
OBJECTIVE
To evaluate the potential of diffusion-weighted (DW) magnetic resonance (MR) imaging with an apparent diffusion coefficient (ADC) map in the prediction of response to neoadjuvant chemotherapy in patients with breast cancer.


METHODS
This retrospective study was approved by the institutional review board, which waived the informed consent requirement. Fifty-three consecutive women (mean age, 43.7 years; median age, 42.0 years; age range, 24-65 years) with 53 invasive breast cancers (mean diameter, 5.0 cm; median diameter, 4.2 cm; diameter range, 2.0-13.3 cm) who had undergone chemotherapy were included. Both DW MR imaging (b values, 0 and 750 sec/mm(2)) and dynamic contrast material-enhanced (DCE) MR imaging were performed at 1.5 T before and after chemotherapy prior to surgery. Mean time from initiation of chemotherapy to posttreatment ADC measurement was 54 days (range, 48-62 days). Average ADC for three regions of interest per tumor on ADC maps was calculated. Patients with a reduction in tumor diameter of at least 30% after chemotherapy at DCE MR imaging were defined as responders. Pretreatment ADCs and percentage increases in ADC after chemotherapy in responders and nonresponders were compared. The best pretreatment ADC cutoff with which to differentiate between responders and nonresponders was calculated with receiver operating characteristic curve analysis.


RESULTS
After chemotherapy, 36 (68%) patients were classified as responders, and 17 (32%) were classified as nonresponders. Pretreatment mean ADC ([1.036 ± 0.015] × 10(-3) mm(2)/sec [standard error]) of responders was significantly lower than that of nonresponders ([1.299 ± 0.079] × 10(-3) mm(2)/sec) (P = .004). Furthermore, mean percentage ADC increase of responders (47.9% ± 4.8) was higher than that of nonresponders (18.1% ± 4.5) (P < .001). The best pretreatment ADC cutoff with which to differentiate between responders and nonresponders was 1.17 × 10(-3) mm(2)/sec, which yielded a sensitivity of 94% (95% confidence interval [CI]: 81%, 99%) and a specificity of 71% (95% CI: 44%, 90%).


CONCLUSIONS
Patients with breast cancer and a low pretreatment ADC tended to respond better to chemotherapy. Prediction of response to neoadjuvant chemotherapy with DW MR imaging might help physicians individualize treatments and avoid ineffective chemotherapy.
Park
Sang Hee
SH
Department of Radiology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea.
Moon
Woo Kyung
WK
Cho
Nariya
N
Song
In Chan
IC
Chang
Jung Min
JM
Park
In-Ae
IA
Han
Wonshik
W
Noh
Dong-Young
DY
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D017024:Chemotherapy, Adjuvant; D003287:Contrast Media / Q000008:administration & dosage; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009361:Neoplasm Invasiveness; D011237:Predictive Value of Tests; D012372:ROC Curve; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D016896:Treatment Outcome
D003287:Contrast Media