107P Application of contrast clearance analysis (CCA) to assess viable tumour in non-small cell lung cancer (NSCLC) brain metastases post-stereotactic radiosurgery (SRS)

Abstract

Brain metastases are a frequent complication in NSCLC. SRS is a non-invasive precision brain metastases treatment. Magnetic resonance imaging (MRI) with contrast-enhanced sequences forms the mainstay of brain metastasis imaging. On MRI post-SRS it can be difficult to differentiate viable tumour from post-treatment change such as radionecrosis. MRI technique CCA aims to distinguish vascular tumour from non-vascular post-treatment change with delayed contrast enhanced images (Zach Neuro Onc 2015). Retrospective review of patients in Royal Marsden Hospital with CCA scan from 1/1/2018 – 1/9/2021. 54 patients, with median of 65 years (range 32 - 89); 87% adenocarcinoma, 5.6% squamous cell carcinoma and 7.5% NSCLC “other”. Patients received up to 7 lines of systemic treatment. Twenty patients had targeted treatments (ALK, EGFR or ROS1). 51 patients received SRS (range 1-6), 10 patients whole brain radiotherapy (WBRT), 23 patients surgical resection (range of 1-2) and 2 patients partial brain radiotherapy. CCA imaging was performed during systemic treatment (47 patients) and during monitoring off treatment (30 patients). During these periods there was a median of 1 CCAs (range 1-7). Systemic therapy continued for median of 7 months from CCA. In 47% CCA concluded viable tumour was present, 53% CCA concluded post SRS changes. Recommended action was monitoring (49 cases), surgery (7 cases), SRS (12 cases), systemic therapy change (6 cases), WBRT (1 case). In the 7 cases where patients underwent resection of presumed tumour, 4 patients had viable tumour and 3 radionecrosis on histology. CCA was performed an average of 30 days prior to surgery. Two cases of radionecrosis, reported in 2017, were reclassified on retrospective review. CCA provided evidence to proceed to brain management. Patients were maintained on systemic therapy for multiple lines of therapy. There was not complete concordance with histology; recent recommendations to perform CCA within 14 days of surgery and evolving expertise in reporting means concordance is likely higher. Prospective validation including impact on patient outcome is warranted.