Role of MRI in osteosarcoma for evaluation and prediction of chemotherapy response: correlation with histological necrosis.
BACKGROUND
Histological necrosis, the current standard for response evaluation in osteosarcoma, is attainable after neoadjuvant chemotherapy.


OBJECTIVE
To establish the role of surrogate markers of response prediction and evaluation using MRI in the early phases of the disease.


METHODS
Thirty-one treatment-naïve osteosarcoma patients received three cycles of neoadjuvant chemotherapy followed by surgery during 2006-2008. All patients underwent baseline and post-chemotherapy conventional, diffusion-weighted and dynamic contrast-enhanced MRI. Taking histological response (good response ≥90% necrosis) as the reference standard, various parameters of MRI were compared to it. A tumor was considered ellipsoidal; volume, average tumor plane and its relative value (average tumor plane relative/body surface area) was calculated using the standard formula for ellipse. Receiver operating characteristic curves were generated to assess best threshold and predictability. After deriving thresholds for each parameter in univariable analysis, multivariable analysis was carried out.


RESULTS
Both pre-and post-chemotherapy absolute and relative-size parameters correlated well with necrosis. Apparent diffusion coefficient did not correlate with necrosis; however, on adjusting for volume, significant correlation was found. Thus, we could derive a new parameter: diffusion per unit volume.


CONCLUSIONS
In osteosarcoma, chemotherapy response can be predicted and evaluated by conventional and diffusion-weighted MRI early in the disease course and it correlates well with necrosis. Further, newly derived parameter diffusion per unit volume appears to be a sensitive substitute for response evaluation in osteosarcoma.
Bajpai
Jyoti
J
Department of Medical Oncology, All India Institute of Medical Sciences, Dr. B. R. A. Institute Rotary Cancer Hospital, New Delhi, 110029, India.
Gamnagatti
Shivanand
S
Kumar
Rakesh
R
Sreenivas
Vishnubhatla
V
Sharma
Mehar Chand
MC
Khan
Shah Alam
SA
Rastogi
Shishir
S
Malhotra
Arun
A
Safaya
Rajni
R
Bakhshi
Sameer
S
D000293:Adolescent; D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000188:drug therapy* / Q000473:pathology* / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D020360:Neoadjuvant Therapy; D012516:Osteosarcoma / Q000188:drug therapy* / Q000473:pathology* / Q000601:surgery; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D016896:Treatment Outcome
D003287:Contrast Media; D019786:Gadolinium DTPA