Background: Stereotactic biopsy is increasingly performed on brain metastases (BrM) as improving cancer outcomes drive aggressive multimodality treatment, however the risk of tract recurrence for such biopsies, in both the upfront and recurrent settings, are poorly defined in an era defined by focused-irradiation paradigms. As such, the rate of tract recurrence was evaluated.
Methods: A retrospective review was performed to identify stereotactic biopsies performed for BrM at Memorial Sloan Kettering Cancer Center from 2002-2020. Data including surgical indications, tumor type, radiographic characteristics, stereotactic planning, pre- and post-operative CNS-directed and systemic treatments, and clinical courses were collected. Recurrence was evaluated using RANO-BM criteria.
Results: Four-hundred-and-seventy-nine patients underwent stereotactic intracranial biopsy for any diagnosis ( >80% were for gliomas or CNS lymphoma). Twenty-two (4.5%) were for pathologically-confirmed viable BrM and 91% of these underwent postoperative irradiation with either stereotactic radiotherapy (14/20, 70%; SBRT) in plans that did not specifically target the biopsy tract, or whole-brain irradiation (6/20, 30%; WBRT). Eleven patients (50%) had >/=3 months radiographic follow-up (median 11.9; 4.5-30.6), of which 6 (55%) developed discontinuous enhancement along the tract at a median 6.4 months (2.3-17.1) post-biopsy. Of these, 2 had previously been treated with SBRT and were sampled in the setting of diagnostic ambiguity (one additionally with WBRT for small cell carcinoma) and underwent intraoperative laser interstitial thermal therapy (LITT) immediately following biopsy. The remainder were treated with SBRT +/- LITT (n=3 and 4, respectively) following biopsy. Tract recurrences were treated with resection (n=2, both with pathologic confirmation), re-irradiation (n=1) or observation/systemic therapy.
Conclusions: In this largest reported series of biopsied BrM, we identify a nontrivial rate, higher than previously described, of recurrence along stereotactic biopsy tracts. As BrM are most commonly treated with focused radiotherapy centered on enhancing tumor margins, consideration should be made to include biopsy tracts where feasible.