Volumetric response of progressing post-SRS lesions treated with laser interstitial thermal therapy

Abstract

We analyzed volumetric response of metastatic brain tumors that progressed despite treatment with stereotactic radiosurgery (SRS) after treatment with laser interstitial thermal therapy (LITT). We retrospectively reviewed consecutive patients treated from 1/2012 to 10/2015 with LITT for metastatic brain tumors demonstrating progression after SRS. Volumes were quantified using MRI with contrast-enhanced T1-weighted (T1W) and fluid-attenuated inversion recovery (FLAIR). Fifty lesions from 36 patients were studied. Lesions were assessed prior to LITT, immediately after LITT, 0-90 days after LITT, 90-180 days after LITT, 180-270 days after LITT, and 270-360 days after LITT. The median T1W volume was 5.05 cc (range 0.54-23.31 cc) before LITT treatment (n = 50), 7.70 cc (range 1.72-38.76 cc) 0-90 days after LITT (n = 47), and 3.68 cc (range 1.282-48.31 cc) 180-270 days after LITT (n = 21). The median FLAIR volume was 43.36 cc (range 3.09-233.01 cc) before LITT treatment (n = 50), 37.13 cc (range 3.48-244.23 cc) 0-90 days after LITT (n = 43), 31.68 cc (range 1.6-248.75 cc) 180-270 days after LITT (n = 18). The 6-month FLAIR volume showed a statistically significant reduction compared to pretreatment (p = 0.04). After selecting for cases where patients had two or more post-operative MRIs, we found that 24 lesions (63%) demonstrated an overall downward trend and 14 lesions (37%) demonstrated an upward trend. The median pre-treatment T1W volume for the patients whose lesions demonstrated volumetric reduction after LITT was 3.54 cc (range 0.539-10.06 cc) and for those who did not demonstrate volumetric reduction after LITT it was 8.81 cc (range 0.926-23.313 cc). The pre-treatment tumor volume plays a significant role in determining response to LITT with smaller tumor volumes responding better to LITT than tumors with larger volumes.

Keywords: Brain metastasis; Laser interstitial thermal therapy; Metastatic; Post-SRS; Stereotactic radiosurgery.

Figure 1

T1W post contrast lesion volumes plotted against days after LITT procedure. These 31 cases demonstrated a decrease in lesion volume over time.

Figure 2

T1W (contrast) lesion volumes plotted against days after LITT procedure. These 19 cases demonstrated an increase in lesion volume over time.

Figure 3

T1W post contrast MRI scans demonstrating a successful response to LITT over time. A) Pre-SRS demonstrating lesion in the posterior left parieto-occipital region, B) Post-SRS showing initial response, C) Pre-LITT lesion showing enlargement of the lesion. D) Intraoperative placement of laser fiber within the lesion, E) Increase in lesion size immediately Post-LITT. F) One-month post-LITT, G) three months post-LITT, H) Six months post LITT showing near total resolution of the lesion.

Figure 4

T1W post contrast MRI scans demonstrating an unsuccessful response to LITT over time. A) Pre-SRS demonstrating lesion in the right frontal region, B) Post-SRS showing initial response. C) Pre-LITT lesion showing enlargement of the lesion. D) Intraoperative placement of laser fiber within the lesion, E) Increase in lesion size immediately Post-LITT. F) One-month post-LITT showing continued enlargement, G) three months post-LITT showing continued enlargement, H) Six months post LITT showing continued enlargement and extension toward the ventricle.

Figure 5

Pre-operative and first post-operative T1W post contrast volumes plotted against days after LITT.