ARRS 2022 Abstracts


E1521. Comparison of Primary Tumor and Metastatic Lesion Response to Targeted Systemic Therapy in Metastatic Renal Cell Carcinoma (mRCC)
  1. Shannon Yoo; UCLA, Los Angeles
  2. Kathleen Ruchalski; UCLA, Los Angeles
  3. Hyun J. Kim; UCLA, Los Angeles
  4. Bianca Villegas; UCLA, Los Angeles
  5. Jonathan Goldin; UCLA, Los Angeles
Targeted systemic therapies have demonstrated survival benefits in metastatic renal cell carcinoma (mRCC). Isolated evaluation of the primary kidney tumor denotes treatment response associated with prolonged survival. Our aim was to compare the paired differences in treatment response rates between the measurable primary kidney tumor and metastatic lesions in patients with mRCC.

Materials and Methods:
A retrospective review of anonymized patients enrolled in phase 3 clinical trials was performed. Subjects were included when having at least one measurable kidney lesion and one metastatic lesion on baseline and at least one follow-up CT or MRI of the chest, abdomen, and pelvis (CAP). All CAP images were assessed by RECIST 1.1 per trial protocol. The sum of target lesion diameters was calculated for each subject. Objective response rate (ORR) was calculated for all target lesions and for the primary kidney lesion and metastatic non-kidney disease separately. At least 30% decrease in tumor size per RECIST 1.1 was required to meet criteria for response. A paired t-test was used to compare depth of response.

A total of 75 patients met inclusion criteria with an average of three target lesions measuring an average of 38.98 mm in size, with 13.33% ORR and 6.7 months (median) progression free survival. Best overall response (BOR) occurred for 10 (13.33%), 25 (33.33%), and 40 (53.33%) patients with partial response, stable disease, and disease progression, respectively. In partial responders, ORR did not differ for primary kidney lesion and metastases. There was no significant difference in depth of response for kidney and non-kidney disease (p = 0.10). For partial responders, kidney lesion mean response was –34.92% (–20.36 mm, SD: 16.39) versus –42.25% (–35.23 mm, SD: 12.41). In those with stable disease, kidney lesion mean response was –11.95% (–5.55 mm, SD: 6.18) versus –10.99% (–10.13, SD: 14.99).

Targeted systemic therapies decrease the size of both the primary kidney lesion and non-primary target lesions. Slightly greater reduction in non-primary metastatic target lesion disease was not significant and did not alter RECIST 1.1 objective response.