Abstract
BackgroundWhile the optimal combination of whole-brain radiotherapy (WBRT), stereotactic radiosurgery (SRS) and surgical resection in the treatment of brain metastases, is controversial, the addition of SRS to surgical resction of solitary metastasis may enhance local control while potentially minimizing toxicity associated with adjuvant WBRT. This study seeks to determine whether pre-operative SRS to the lesion versus post-operative SRS to the resection bed may reduce irradiation of adjacent normal brain tissue.MethodsA retrospective study of 12 patients with 13 surgically resected cerebral metastases was performed. The pre-operative contrast-enhancing tumors and post-operative resection cavities plus any enhancing residual disease were contoured to yield the gross target volume (GTV). In turn these GTV’s were uniformly expanded by 3-mm to generate the pre-operative, as well as post-operative planning target volume (PTV.) For each lesion, a 7-static-conformal-beam, non-coplanar plan utilizing 6 MV photons was generated to encompass the PTV within the 85% isodose line. Excess normal brain volume irradiated was defined as the volume outside the GTV receiving the prescribed dose.ResultsWhen lesions were divided into two groups - Group A (pre-operative GTV’s < 15 cc, n = 9) and Group B (pre-operative GTV’s > 15 cc, n = 4) - the average volume of normal brain irradiated was significantly smaller if pre-operative SRS was used for treatment of lesions in Group A (9.5 vs. 16.8 cc, paired t-test, p = 0.0045). In contrast, this volume was smaller for Group B lesions if post-operative SRS was used for treatment of these lesions (27.6 vs. 51.2 cc, p = 0.252). A comparison of groups with respect to mean volume differences between pre- and post-operative SRS was significantly different (two-sample t-test p = 0.016). GTV and the difference between pre- and post-operative volume were highly correlated (Pearson correlation = −0.875, p < 0.0001).ConclusionsPre-operative treatment of smaller metastases may result in reduced radiation dose to normal tissue and, thus, reduced treatment-related morbidity compared to post-operative irradiation of the resection cavity.
Highlights
While the optimal combination of whole-brain radiotherapy (WBRT), stereotactic radiosurgery (SRS) and surgical resection in the treatment of brain metastases, is controversial, the addition of Stereotactic radiosurgery (SRS) to surgical resction of solitary metastasis may enhance local control while potentially minimizing toxicity associated with adjuvant WBRT
In 1990, Patchell et al demonstrated that treatment outcomes of cerebral metastases were better when surgical resection was combined with WBRT [1]
We retrospectively analyzed patients who presented with solitary brain metastases which were resected successfully with gross total resection
Summary
While the optimal combination of whole-brain radiotherapy (WBRT), stereotactic radiosurgery (SRS) and surgical resection in the treatment of brain metastases, is controversial, the addition of SRS to surgical resction of solitary metastasis may enhance local control while potentially minimizing toxicity associated with adjuvant WBRT. This study seeks to determine whether pre-operative SRS to the lesion versus post-operative SRS to the resection bed may reduce irradiation of adjacent normal brain tissue. Postoperative SRS is used at many institutions in lieu of WBRT for treatment of cerebral metastases This focal radiation technique offers potential advantages over WBRT, which may be associated with acute and delayed adverse effects from irradiation of normal brain parenchyma and which has not been shown to increase overall survival. This conjecture is based on the often irregular shape observed for the post-operative resection cavity This tortuosity and high aspect ratio will result in poorer conformality of the treatment plan compared and, possibly, irradiation of a greater volume of normal adjacent parenchyma than in the case of treatment of the typically “rounder and smoother” pre-operative target. Major benefits of pre-operative SRS may be the reduction of tumor “spill” and subsequent dissemination, as well as irradiation of a better oxygenated and, more radiosensitive target
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