Pre-operative radiotherapy in soft tissue tumors. Assessment of response by static post-contrast MR imaging compared to histopathology.
OBJECTIVE
To evaluate if static post-contrast MR imaging was adequate to assess tumor viability after pre-operative radiotherapy in soft tissue sarcoma.


METHODS
Post-contrast MR imaging of 36 soft tissue sarcomas performed 0-54 days (median 13 days) after pre-operative radiotherapy, were retrospectively reviewed and compared to post-operative histopathology reports. The contrast enhancement of the tumor was visually graded as minor, moderate or extensive. From the post-operative histopathology reports, three types of tumor response to radiotherapy were defined: Poor, intermediate or good. The size of the tumors before and after radiation was compared.


RESULTS
Even if most viable tumors enhanced more than non-viable tumors, there was major overlapping and significant contrast enhancement could be seen in tumors where histopathological examination revealed no viable tumor tissue. Based on histopathology, there were 12 good responders; 8 of these showed minor, 3 moderate and 1 extensive contrast enhancement on MR imaging. Sixteen tumors had an intermediate response; 3 showed minor, 8 moderate and 5 extensive enhancement. Eight tumors had poor response; none showed minor enhancement, 3 moderate and 5 extensive enhancement. Both increase and decrease in tumor size was seen in lesions with a good therapy response.


CONCLUSIONS
Static post-contrast MR imaging cannot reliably assess tumor viability after pre-operative radiotherapy in soft tissue sarcoma. In tumors with no viable tumor tissue, moderate and extensive contrast enhancement can be seen.
Einarsdottir
H
H
Department of Radiology, Karolinska Hospital, Stockholm, Sweden.
Wejde
J
J
Bauer
H C
HC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000494:pharmacology*; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007866:Leg / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011300:Preoperative Care / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012509:Sarcoma / Q000175:diagnosis / Q000532:radiotherapy* / Q000601:surgery; D012983:Soft Tissue Neoplasms / Q000175:diagnosis / Q000532:radiotherapy* / Q000601:surgery
D003287:Contrast Media; D019786:Gadolinium DTPA