Radiation response: an additional unique signature of myxoid liposarcoma.
OBJECTIVE
Historically, myxoid liposarcoma (MLS) has been reported to show a marked clinical response to radiotherapy (RT), but objective data to support that contention have been lacking. We performed a retrospective analysis of the response of a group of MLS tumors to preoperative RT using tumor dimensions calculated from pretreatment imaging and the subsequent surgical specimen obtained approximately 1 month after RT.


METHODS
Data were abstracted from the Princess Margaret Hospital prospective database on a series of patients with MLS who had undergone preoperative RT between 1991 and 1999. A group of malignant fibrous histiocytoma (MFH) patients treated on the same protocol served as controls. Pretreatment and posttreatment three-dimensional measurements were obtained; comparison tumor volume measurements were estimated using the ellipsoid formula, and the analysis was also repeated using the maximal tumor dimension. Identical measurement procedures were used for the MLS (experimental) and MFH (control) cases.


RESULTS
A total of 16 MLS tumor specimens were available for analysis, and 16 MFH cases were randomly chosen for comparison. The mean pretreatment and posttreatment volume of the MLS tumors was 415 and 199 cm(3), respectively (P = <0.0001). The mean pretreatment and posttreatment volume of the MFH tumors was 264 and 273 cm(3), respectively (p = 0.804). The proportional reduction in the median tumor volume was 59% and -7% for MLS and MFH tumors, respectively. Both the absolute and the proportional reduction in volume for MLS tumors vs. MFH tumors was statistically significant (p = 0.006 and p = 0.002, respectively).


CONCLUSIONS
These results provide the first objective data to support the idea that MLS tumors show a statistically significant reduction in size when treated with RT and that this response is greater than that of MFH tumors given the same RT. These results may be relevant to the management of MLS with combined RT and surgery in difficult anatomic situations in which adequate surgical excision is not feasible. They also confirm another unique characteristic of this unusual subtype of soft tissue sarcoma.
Pitson
Graham
G
Department of Radiation Oncology, Princess Margaret Hospital, Toronto, ON, Canada.
Robinson
Philip
P
Wilke
Derek
D
Kandel
Rita A
RA
White
Larry
L
Griffin
Anthony M
AM
Bell
Robert S
RS
Catton
Charles N
CN
Wunder
Jay S
JS
O'Sullivan
Brian
B
D000328:Adult; D000368:Aged; D018219:Histiocytoma, Benign Fibrous / Q000532:radiotherapy; D006801:Humans; D018208:Liposarcoma, Myxoid / Q000473:pathology / Q000532:radiotherapy*; D008875:Middle Aged; D011879:Radiotherapy Dosage; D012189:Retrospective Studies