Impact of regular magnetic resonance imaging follow-up after stereotactic radiotherapy to the surgical cavity in patients with one to three brain metastases

Abstract

BackgroundAdministering stereotactic radiotherapy to the surgical cavity and thus omitting postoperative whole brain radiotherapy (WBRT) is a favored strategy in limited metastatic brain disease. Little is known about the impact of regular magnetic resonance imaging follow-up (MRI FU) in such patient cohorts. The aim of this study is to examine the impact of regular MRI FU and to report the oncological outcomes of patients with one to three brain metastases (BMs) treated with stereotactic radiosurgery (SRS) or hypo-fractionated stereotactic radiotherapy (HFSRT) to the surgical cavity.MethodsWe retrospectively analyzed patients who received SRS or HFSRT to the surgical cavity after resection of one to two BMs. Additional, non-resected BMs were managed with SRS alone. Survival was estimated by the Kaplan-Meier method. Prognostic factors were examined with the log-rank test and Cox proportional hazards model. Regular MRI FU was defined as performing a brain MRI 3 months after radiotherapy (RT) and/or performing ≥1 brain MRI per 180 days. Primary endpoint was local control (LC). Secondary endpoints were distant brain control (DBC), overall survival (OS) and the correlation between regular MRI FU and overall survival (OS), symptom-free survival (SFS), deferment of WBRT and WBRT-free survival (WFS).ResultsOverall, 75 patients were enrolled. One, 2 and 3 BMs were seen in 63 (84%), 11 (15%) and 1 (1%) patients, respectively. Forty (53%) patients underwent MRI FU 3 months after RT and 38 (51%) patients received ≥1 brain MRI per 180 days. Median OS was 19.4 months (95% CI: 13.2–25.6 months). Actuarial LC, DBC and OS at 1 year were 72% (95% CI: 60–83%), 60% (95% CI: 48–72%) and 66% (95% CI: 53–76%), respectively. A planning target volume > 15 cm3 (p = 0.01), Graded Prognostic Assessment (GPA) score (p = 0.001) and residual tumor after surgery (p = 0.008) were prognostic for decreased OS in multivariate analysis. No significant correlation between MRI FU at 3 months and OS (p = 0.462), SFS (p = 0.536), WFS (p = 0.407) or deferment of WBRT (p = 0.955) was seen. Likewise, performing ≥1 MRI per 180 days had no significant impact on OS (p = 0.954), SFS (p = 0.196), WFS (p = 0.308) or deferment of WBRT (p = 0.268).ConclusionOur results regarding oncological outcomes consist with the current data from the literature. Surprisingly, regular MRI FU did not result in increased OS, SFS, WFS or deferment of WBRT in our cohort consisting mainly of patients with a single and resected BM. Therefore, the impact of regular MRI FU needs prospective evaluation.Trial registrationProject ID: 2017–00033, retrospectively registered.

Current status and recent advances in resection cavity irradiation of brain metastases

“…In the Brown trial [ 7 ], local control decreased for postoperative cavity volumes > 20 ml who received radiation doses < 15 Gy, being significantly lower than that observed after WBRT. A significantly better local control with radiation dose ≥ 18 Gy has been observed in other retrospective studies [ 14 , 16 , 23 , 42 ]. It needs to be added that data discussed above do not allow a separate analysis of SRS dose versus volume, as larger volumes were consistently treated with lower SRS doses because of concerns of toxicity.…”

“…Factors associated with longer survival include Karnofsky Performance Status (KPS) score of 80% or greater, an interval less than 4 weeks between resection and postoperative radiation treatment [ 45 , 46 ], and a controlled primary tumor [ 8 , 24 , 30 , 36 ]. In contrast, combined systemic treatment and histology did not emerge as independent prognostic factors for either local control or survival in most studies [ 8 , 23 , 25 , 35 , 36 , 41 ] .…”

“…The clinical success of SRS in patients presenting with a limited number of brain metastases resulted in its application to surgical cavities as an alternative to WBRT. Several retrospective studies reported local control and overall survival rates of 70% to 90% and of 50% to 70% at 12 months, respectively, following either SRS (Table 1 ) [ 7 , 8 , 10 – 23 ] and HSRT (Table 2 ) [ 24 – 37 ]. The question on the efficacy and safety of postoperative SRS has been recently addressed in two randomized trials comparing postoperative SRS to observation or to WBRT, respectively [ 7 , 8 ].…”

“…Several studies have evaluated the impact of different prognostic factors on local tumor control following radiation to the resection cavity. Larger preoperative tumor size and cavity volumes greater than 3 cm [ 7 , 8 , 12 , 14 , 15 , 26 , 29 , 39 – 41 ], incomplete resection [ 18 , 33 , 41 , 42 ], lower radiation dose [ 14 , 16 , 23 , 40 , 41 , 43 ], pretreatment tumor volume in contact with dura [ 15 , 26 , 44 ], and longer interval time between surgery and radiation treatment [ 16 , 45 , 46 ] have been significantly correlated with worse local control. Factors associated with longer survival include Karnofsky Performance Status (KPS) score of 80% or greater, an interval less than 4 weeks between resection and postoperative radiation treatment [ 45 , 46 ], and a controlled primary tumor [ 8 , 24 , 30 , 36 ].…”

“…A significant correlation between the radiation dose and local control has been observed for both SRS and HSRT [ 7 , 8 , 14 , 16 , 23 , 35 , 40 , 42 , 43 ]. In the Mahajan trial [ 8 ], SRS prescription doses were 16, 14, and 12 Gy for target volumes of ≤ 10 ml, 10.1–15 ml, and > 15 ml, respectively, given in a single session by Gamma Knife.…”