The additive value of morphologic grouping in assessing treatment response to ablative radiation therapy in liver
Maria El Homsi1, Dina Hamdan2,3, Firas S Ahmed2
1Memorial Sloan Kettering Cancer Center, New York, USA. elhomsim@mskcc.org.
Objectives:
To assess the utility of Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 and a modified version of previously proposed morphologic grouping in assessing treatment response to ablative radiotherapy in liver metastases.
Methods:
This retrospective, single-institution study included consecutive patients with liver metastases who were treated with ablative radiotherapy and who underwent at least two follow-up abdominal contrast-enhanced CT scans from January 2017-November 2021. Two abdominal radiologists independently assessed baseline and follow-up scans based on RECIST 1.1 and a modified version of morphologic grouping originally proposed by the University of Texas MD Anderson Cancer Center. The association between each response assessment method with durable local control (i.e., decreased treated tumor size after radiation and stability over > 1 year on follow-up imaging with no progression of disease) and overall survival was assessed using multivariable generalized estimating equations and the univariable Cox proportional hazards model, respectively.
Results:
Of 33 patients (17 men and 16 women; mean age at baseline, 63 years (range, 28-84); median follow-up, 368 days), 19/33 (58%) had durable local control. Modified morphologic grouping at the second, third, and fourth follow-up timepoints was associated with durable local control (P = 0.009, < 0.001, < 0.001, for Reader 1, and 0.003, < 0.001, < 0.001 for Reader 2). RECIST 1.1 at the third and fourth follow-up timepoints was associated with durable local control (P = 0.007 and 0.004 for Reader 1, and 0.008 and 0.01 for Reader 2). Neither was associated with overall survival (P = 0.15-0.24).
Conclusion:
Modified morphologic grouping-based response assessment of liver metastases treated with ablative radiotherapy may enable early detection of durable local control when compared to RECIST 1.1, especially at early follow-up timepoints.
