A phase 2 trial of stereotactic radiosurgery boost after surgical resection for brain metastases

Abstract

Purpose: To evaluate local control after surgical resection and postoperative stereotactic radiosurgery (SRS) for brain metastases.

Methods and materials: A total of 49 patients (50 lesions) were enrolled and available for analysis. Eligibility criteria included histologically confirmed malignancy with 1 or 2 intraparenchymal brain metastases, age≥18 years, and Karnofsky performance status (KPS)≥70. A Cox proportional hazard regression model was used to test for significant associations between clinical factors and overall survival (OS). Competing risks regression models, as well as cumulative incidence functions, were fit using the method of Fine and Gray to assess the association between clinical factors and both local failure (LF; recurrence within surgical cavity or SRS target), and regional failure (RF; intracranial metastasis outside of treated volume).

Results: The median follow-up was 12.0 months (range, 1.0-94.1 months). After surgical resection, 39 patients with 40 lesions were treated a median of 31 days (range, 7-56 days) later with SRS to the surgical bed to a median dose of 1800 cGy (range, 1500-2200 cGy). Of the 50 lesions, 15 (30%) demonstrated LF after surgery. The cumulative LF and RF rates were 22% and 44% at 12 months. Patients who went on to receive SRS had a significantly lower incidence of LF (P=.008). Other factors associated with improved local control include non-small cell lung cancer histology (P=.048), tumor diameter<3 cm (P=.010), and deep parenchymal tumors (P=.036). Large tumors (≥3 cm) with superficial dural/pial involvement showed the highest risk for LF (53.3% at 12 months). Large superficial lesions treated with SRS had a 54.5% LF. Infratentorial lesions were associated with a higher risk of developing RF compared to supratentorial lesions (P<.001).

Conclusions: Postoperative SRS is associated with high rates of local control, especially for deep brain metastases<3 cm. Tumors≥3 cm with superficial dural/pial involvement demonstrate the highest risk of LF.

Figure 1

Comparison of the cumulative incidence of local failure in patients with non-small cell lung cancer primary vs. others.

Figure 2

Incidence of local failure categorized by tumor depth and size.

Figure 3

Forty-four year-old gentleman with metastatic melanoma presented with a large (≥3 cm), superficial brain metastasis (A). He then underwent resection and SRS of post-resection cavity (B), but was then found to have local recurrence at the anterior border of the surgical cavity 7 months later (C). The images are on the same anatomical level. Image B also shows isodose distribution of the treated cavity, prescribed to1500 cGy to the 80% isodose line. The pink line represents the CTV, and red line represents the PTV.