Role of soft tissue metastases on tumor progression in castrate-resistant metastatic prostate cancer.

Abstract

214 Background: While visceral metastases in castrate resistant prostate cancer (mCRPC) are a negative prognostic factor, patients may still derive treatment benefits. Given varying anatomic sites of tumor may display differing treatment responses we investigated the role of soft tissue metastases in progressive disease (PD) by anatomic site. Methods: A retrospective review of anonymized patients enrolled in phase 3 clinical trials was performed. Patients were excluded if lacked Tc bone scan or CT chest, abdomen and pelvis (CT CAP) on trial. Subjects were included if they had soft tissue disease per RECIST 1.1. Bone disease was defined by automated BSLA criteria. All CT CAPs per clinical trial protocol were assessed by RECIST 1.1. Soft tissue PD was noted as target|nontarget lesion growth and/or presence of new lesions by anatomic site. Bone PD was defined by >20% increase in BSLA score. Results: Of 322 total patients, 138 met criteria of soft tissue disease at baseline. Baseline anatomic sites of metastases per RECIST included: visceral (74, 53.6%), lymph node only (52, 37.7%) and soft tissue bone (12, 7.1%). PD occurred in 46 patients with baseline soft tissue disease; with PD first detected by BSLA (23, 16.7 %), RECIST (19, 13.8 %) or with PD occurring simultaneously by BSLA and RECIST (4, 2.9%). Of the 138 patients with baseline soft tissue disease, PD occurred by RECIST in 25 patients. This occurred due to worsening visceral (11, 68.8%), lymph node (4, 25.0%) or soft tissue bone (1, 6.3%) disease. PD by new lesions only occurred in 9 patients (36.0%), as a result of 77.8% visceral and 22.2% lymph node. Conclusions: In mCRPC with soft tissue disease at baseline, progression by BSLA bone score still accounts for a large portion of PD. Further analyses must be performed to better differentiate disease phenotypes amongst mCRPC with combined visceral/osseous disease.