Gamma Knife to the surgical resection bed for intracranial metastases: do tumor diameter and treatment volume matter?Michelle Alonso-Basanta1, John Lukens2, Jay Dorsey2, John YK Lee31Philadelphia, United States 2Department of Radiation Oncology, University of Pennsylvania, Philadelphia, USA 3University of Pennsylvania Keywords: brain metastasis, resection, gamma knife, outcome, radiosurgery
Stereotactic radiosurgery (SRS) is an emerging alternative to whole brain irradiation (WBI) after resection of intracranial metastases.
However, the literature disagrees about the prognostic significance of pre-operative largest tumor diameter and SRS treatment volume with respect to local failure rate and need for salvage WBI. We sought to clarify these factors.
Thirty patients had imaging follow-up and were included in this study. Twenty-six patients (87%) had no prior history of intracranial surgery or radiation. One patient underwent re-resection prior to GK. Three patients received WBI after a prior resection, recurred locally, and went on to re-resection and GK.
We retrospectively reviewed the SRS experience for intracranial metastases at Pennsylvania Hospital from 2006-2010. Of 435 total patients, 34 received Gamma Knife (GK) to the resection bed after removal of a single lesion.
The most common primary tumors were non-small cell lung (50%), melanoma (23%), and breast (20%). The median pre-operative tumor diameter was 2.75 cm (range 0.8-5.5). A median dose of 16 Gy (range 13-21) was prescribed to the 50% isodose line to a median volume of 11.1 cm3 (range 2.5-34.7). Twenty patients (67%) received GK to the resection bed alone, while 10 (33%) were simultaneously treated for 1-2 synchronous metastases. With a median follow-up of 13.9 months, patients survived a median 14.5 months from GK. Local treatment failure occurred in 7 cases (23%) and distant intracranial failure in 21 (70%). Thirteen patients (43%) underwent salvage WBI at a median of 5.2 months (range 1.5-26.6) after GK. Five of 13 patients (38%) with a pre-operative tumor diameter > 3 cm failed locally, versus 2 of 17 (12%) with a diameter ? 3 cm (p = 0.19). Diameter did not predict for subsequent salvage WBI (p = 0.72). SRS treatment volume, analyzed as a continuous variable and as > or ? 11 cm3, did not predict for local failure or salvage WBI.
This was a retrospective study.
SRS to the resection bed spares many patients WBI and delays it for others.
Our experience supports the view that pre-operative tumor diameter > 3 cm may predict for local failure. SRS treatment volume did not impact local failure or salvage WBI. Project Roles:
M. Alonso-Basanta (), J. Lukens (), J. Dorsey (), J. Lee ()