(P 334) MRI VOLUMETRIC AND MODIFIED CHOI-BASED ASSESSMENT OF TREATMENT RESPONSE IN EXTREMITY DESMOID TUMORS TREATED WITH NIROGACESTAT OR SORAFENIB

Author(s)

Raul F. Valenzuela, MD

Assistant Professor Musculoskeletal Radiology
MD Anderson Cancer Center
Houston, Texas, United States

Co-Author(s)

Elvis de Jesus Duran Sierra, PhD (he/him/his)

Data Scientist
The University of Texas MD Anderson Cancer Center
Houston, Texas, United States
Mathew A. Canjirathinkal, MD

Research Assistant
The University of Texas MD Anderson Cancer Center
Hosuton, Texas, United States
CC

Colleen M Costelloe, MD

The University of Texas MD Anderson Cancer Center
Houston, Texas, United States
JM

John E. E. Madewell, MD

The University of Texas MD Anderson Cancer Center
Houston, Texas, United States
William A. A. Murphy Jr., Jr., MD (he/him/his)

Profesor Musculoskeletal Imaging
The University of Texas MD Anderson Cancer Center
Houston, Texas, United States
Behrang Amini, MD, PhD

Professor Musculoskeletal Imaging
The University of Texas MD Anderson Cancer Center
Houston, Texas, United States
JE

Jossue Espinoza, MD

The University of Texas MD Anderson Cancer Center
Houston, Texas, United States

Objective: Desmoid fibromatosis patients are typically treated with active surveillance and with drugs on progression, particularly sorafenib and, most recently, with nirogacestat. This study aimed to determine the objective signal and volume changes under therapy and over time, comparing both drugs using volumetric and modified Choi (mChoi) measurements.

Methods: This study included 17 patients with single-lesion extremity desmoid fibromatosis with standard-of-care MRI from March 2021-February 2024. Volumetric tumor segmentations were created on T2-STIR images, and diameter, mChoi, and volume measurements were computed at four time points: Pre-treatment (Pre-Rx), post-treatment 1 (Rx1), post-treatment 2 (Rx2), and post-treatment 3 (Rx3). The percentage change in diameter (RECIST), mChoi, and volume across time were computed with respect to Rx1 and compared in nirogacestat vs. sorafenib patients.

Results: Nirogacestat group (8 patients):
o mChoi detected two progressions not detected by RECIST or volume.
o From Pre-Rx to Rx1, the average mChoi decreased by 62% over 14 months, representing its maximum slope. From Pre-Rx to Rx3, the mChoi decreased by 66% over a period of 20 months of observation (-3.3%/month).
o From Pre-Rx to Rx1, the average volume decreased by 17% over 14 months (maximum slope), and from Pre-Rx to Rx3, the volume reduced by 49% over a period of observation of 20 months (-2.45%/month).
o By volume and mChoi a sustained response was observed in an average of 3 time points following Pre-Rx (20 months).
Sorafenib group (9 patients):
o mChoi detected one response not detected by RECIST or volume.
o From Pre-Rx to Rx1, the average mChoi decreased by 79% over 23 months, and from Pre-Rx to Rx3, the mChoi decreased by 49% over a period of observation of 34 months (-1.44%/month).
o From Pre-Rx to Rx1, the average volume decreased by 20% over 23 months (maximum slope), and from Pre-Rx to Rx3, the volume decreased by 4% over a period of observation of 34 months (-0.09%/month).
o By volume and mChoi a sustained response was observed in an average of 1 time point following Pre-Rx (23 months).

Conclusion: Patients treated with nirogacestat displayed larger magnitude of volumetric and mChoi changes across treatment, with the fastest positive response (highest slope) and similar period of sustained positive treatment effects compared to patients treated with sorafenib, indicating the potential advantage of nirogacestat as an effective treatment in desmoid tumors.