Five fraction stereotactic radiotherapy after brain metastasectomy: a single-institution experience and literature review

Preoperative radiosurgery for brain metastases (PREOP-1): A feasibility trial

Purpose

Preoperative radiosurgery (SRS) of brain metastases (BM) aims to achieve cavity local control with a reduction in leptomeningeal relapse (LMD) and without additional radionecrosis compared to postoperative SRS. We present the final results of a prospective feasibility trial of linac-based stereotactic radiosurgery (SRS) prior to neurosurgical resection of a brain metastasis (PREOP-1).

Methods

Eligibility criteria included a BM up to 4 cm in diameter for elective resection. The primary endpoint was the feasibility of delivering linac-based preoperative SRS in all patients prior to anticipated gross tumour resection. Secondary endpoints included rates of LMD, local control and overall survival. Exploratory endpoints were the level of expression of immunological and proliferative markers.

Results

Thirteen patients of median age 65 years (range 41-77) were recruited. Twelve patients (92 %) received preoperative radiosurgery and metastasectomy and one patient went directly to surgery and received postoperative SRS, thus the primary endpoint was not met. The median time between referral and preoperative SRS was 6.5 working days (1-10) and from SRS to neurosurgery was 1 day (0-5). The median prescribed dose was 16 Gy (14-19) to a median planning target volume of 12.7 cm3 (5.9-26.1). Five patients completed 12-month follow-up after preoperative SRS without local recurrence or leptomeningeal disease. The patient who received postoperative FSRT developed LMD after six months. There was one transient toxicity (grade 2 alopecia) and nine patients have died from extracranial causes. Patients reported significant improvement in motor weakness at 6 months (P = 0.04). No pattern in changes of marker expression was observed.

Conclusion

In patients with large brain metastasis without raised intracranial pressure, linac-based preoperative SRS was feasible in 12/13 patients and safe in 12/12 patients without any surgical delay or intracranial complications.

Opportunities and Alternatives of Modern Radiation Oncology and Surgery for the Management of Resectable Brain Metastases

Postsurgical radiotherapy (RT) has been early proven to prevent local tumor recurrence, initially performed with whole brain RT (WBRT). Subsequent to disadvantageous cognitive sequalae for the patient and the broad distribution of modern linear accelerators, focal irradiation of the tumor has omitted WBRT in most cases. In many studies, the effectiveness of local RT of the resection cavity, either as single-fraction stereotactic radiosurgery (SRS) or hypo-fractionated stereotactic RT (hFSRT), has been demonstrated to be effective and safe. However, whereas prospective high-level incidence is still lacking on which dose and fractionation scheme is the best choice for the patient, further ablative techniques have come into play. Neoadjuvant SRS (N-SRS) prior to resection combines straightforward target delineation with an accelerated post-surgical phase, allowing an earlier start of systemic treatment or rehabilitation as indicated. In addition, low-energy intraoperative RT (IORT) on the surgical bed has been introduced as another alternative to external beam RT, offering sterilization of the cavity surface with steep dose gradients towards the healthy brain. This consensus paper summarizes current local treatment strategies for resectable brain metastases regarding available data and patient-centered decision-making.

The Management of Oligometastatic Disease in Colorectal Cancer: Present Strategies and Future Perspectives

Oligometastatic disease has been described as an intermediate clinical state between localized cancer and systemically metastasized disease. Recent clinical studies have shown prolonged survival when aggressive locoregional approaches are added to systemic therapies in patients with oligometastases. The aim of this review is to outline the newest options to treat oligometastatic colorectal cancer (CRC), also considering its molecular patterns. We present an overview of the available local treatment strategies, including surgical procedures, stereotactic body radiation therapy (SBRT), thermal ablation, as well as trans-arterial chemoembolization (TACE) and selective internal radiotherapy (SIRT). Moreover, since imaging methods provide crucial information for the early diagnosis and management of oligometastatic CRC, we discuss the role of modern radiologic techniques in selecting patients that are amenable to potentially curative locoregional treatments.

Dosimetric Parameters in Hypofractionated Stereotactic Radiotherapy for Brain Metastases: Do Flattening Filter-Free Beams Bring Benefits? A Preliminary Study

PURPOSE

This study aimed to compare the dosimetric results of flattening filter-free (FFF) vs. flattened (FF) treatment plans for fractionated stereotactic radiotherapy (fSRT), with the goal to highlight potential advantages of FFF beams.

METHODS

A group of 18 patients with brain metastases treated with fSRT (30 Gy delivered in 5 fractions) were included. The dosimetric parameters evaluated were: (1) physical dosimetric parameters (number of monitor units (MUs), conformity index (CI), dose gradient index (DGI), beam on time (BOT)); (2) clinical dosimetric parameters pertaining to target volume (PTV) and organs at risk (OARs). Two treatment plans were performed for all patients: one used 6 MV FFF beams and the other used 6 MV flattened beams.

RESULTS

A slight increase in MUs was observed for the FFF mode (+23.3 MUs). The CI showed a difference of -2.7% for the FF plans (p = 0.28), correlated with a poorer coverage of the PTV. DGI values reported in terms of PTV are in line with international recommendations and showed a +1.9% difference for FFF plans. An average BOT of 90.3 s was reported for FFF plans, which was 2.3 times shorter than that required for FF plans delivery (p ≤ 0.001). A slight decrease of PTV coverage (-1.26%, p = 0.036) for FF plans can be considered relevant, but no other significant differences were observed between the two optimizations. No statistically significant benefit of using FFF beams to reduce V₂₀ for normal brain could be demonstrated.

CONCLUSION

These dosimetric results encourage the implementation of fSRT with standard flattened beams in centers where FFF linacs are not available.

Low-Energy X-Ray Intraoperative Radiation Therapy (Lex-IORT) for Resected Brain Metastases: A Single-Institution Experience

BACKGROUND

Resection followed by local radiation therapy (RT) is the standard of care for symptomatic brain metastases. However, the optimal technique, fractionation scheme and dose are still being debated. Lately, low-energy X-ray intraoperative RT (lex-IORT) has been of increasing interest.

METHOD

Eighteen consecutive patients undergoing BM resection followed by immediate lex-IORT with 16-30 Gy applied to the spherical applicator were retrospectively analyzed. Demographic, RT-specific, radiographic and clinical data were reviewed to evaluate the effectiveness and safety of IORT for BM. Descriptive statistics and Kaplan-Meyer analysis were applied.

RESULTS

The mean follow-up time was 10.8 months (range, 0-39 months). The estimated local control (LC), distant brain control (DBC) and overall survival (OS) at 12 months post IORT were 92.9% (95%-CI 79.3-100%), 71.4% (95%-CI 50.2-92.6%) and 58.0% (95%-CI 34.1-81.9%), respectively. Two patients developed radiation necrosis (11.1%) and wound infection (CTCAE grade III); both had additional adjuvant treatment after IORT. For five patients (27.8%), the time to the start or continuation of systemic treatment was ≤15 days and hence shorter than wound healing and adjuvant RT would have required.

CONCLUSION

In accordance with previous series, this study demonstrates the effectiveness and safety of IORT in the management of brain metastases despite the small cohort and the retrospective characteristic of this analysis.

Stereotactic radiosurgery and radiotherapy for resected brain metastases: current pattern of care in the Radiosurgery and Stereotactic Radiotherapy Working Group of the German Association for Radiation Oncology (DEGRO)

PURPOSE

Preoperative stereotactic radiosurgery (SRS) of brain metastases may achieve similar local control and better leptomeningeal control rates than postoperative fractionated stereotactic radiotherapy (FSRT) in patients treated with elective metastasectomy. To plan a multicentre trial of preoperative SRS compared with postoperative FSRT, a survey of experts was conducted to determine current practice.

METHODS

A survey with 15 questions was distributed to the DEGRO Radiosurgery and Stereotactic Radiotherapy Working Group. Participants were asked under what circumstances they offered SRS, FSRT, partial and/or whole brain radiotherapy before or after resection of a brain metastasis, as well as the feasibility of preoperative stereotactic radiosurgery and neurosurgical resection within 6 days.

RESULTS

Of 25 participants from 24 centres, 22 completed 100% of the questions. 24 respondents were radiation oncologists and 1 was a neurosurgeon. All 24 centres have one or more dedicated radiosurgery platform and all offer postoperative FSRT. Preoperative SRS is offered by 4/24 (16.7%) centres, and 9/24 (37.5%) sometimes recommend single-fraction postoperative SRS. Partial brain irradiation is offered by 8/24 (33.3%) centres and 12/24 (50%) occasionally recommend whole-brain irradiation. Two centres are participating in clinical trials of preoperative SRS. SRS techniques and fractionation varied between centres.

CONCLUSION

All responding centres currently offer postoperative FSRT after brain metastasectomy. Approximately one third offer single-fraction postoperative SRS and four already perform preoperative SRS. With regard to potential co-investigators, 18 were identified for the PREOP‑2 multicentre trial, which will randomise between preoperative SRS and postoperative FSRT.

Histopathology and surgical outcome of symptomatic treatment-related changes after gamma knife radiosurgery in patients with brain metastases

A late-onset treatment-related changes (TRCs), which represent radiographic radiation necrosis (RN), frequently occur after stereotactic radiosurgery (SRS) for brain metastases and often need surgical treatment. This study aimed to validate the true pathology and investigate clinical implication of surgically resected TRCs on advanced magnetic resonance imaging (MRI). Retrospective analyses of 86 patients who underwent surgical resection after radiosurgery of brain metastases were performed. Fifty-four patients displayed TRCs on preoperative MRI, comprising pure RN in 19 patients (TRC-RN group) and mixed viable tumor cells in 35 patients (TRC-PD group). Thirty-two patients revealed the consistent diagnosis of progressive disease in both MRI and histopathology (PD-PD group). The TRC-PD group showed larger prescription isodose volume (9.4 cm3) than the TRC-RN (4.06 cm3, p = 0.014) group and a shorter time interval from SRS to preoperative MRI diagnosis (median 4.07 months) than the PD-PD group (median 8.77 months, p = 0.004). Progression-free survival was significantly different among the three groups (p < 0.001), but not between TRC-RN and TRC-PD (post hoc test, p = 1.00), while no difference was observed in overall survival (p = 0.067). Brain metastases featured as TRCs after SRS frequently contained viable tumor cells. However, this histologic heterogeneity had a minor impact on benign local prognosis of TRCs after surgical resection.

State of affairs regarding targeted pharmacological therapy of cancers metastasized to the brain

In 1999 a visionary short article by The Wall Street Journal writers Robert Langreth and Michael Waldholz popularized the new term "personalized medicine," that is to say, the targeting of drugs to each unique genetic profile. From today's perspective, targeted approaches have clearly found the widest use in the antineoplastic domain. The current review was initiated to review the progress that has been made regarding the treatment of patients with advanced cancer and brain metastases. PubMed was searched for the terms brain metastasis, brain metastases, or metastatic brain in the Title/Abstract. Selection was limited to randomized controlled trial (RCT) and publication date January 2010 to February 2022. Following visual review, 51 papers on metastatic lung cancer, 12 on metastatic breast cancer, and 9 on malignant melanoma were retained and underwent full analysis. Information was extracted from the papers giving specific numbers for intracranial response rate and/or overall survival. Since most pharmacological trials on advanced cancers excluded patients with brain metastases and since hardly any information on adjuvant radiotherapy and radiosurgery is available from the pharmacological trials, precise assessment of the effect of targeted medication for the subgroups with brain metastases is difficult. Some quantitative information regarding the success of targeted pharmacological therapy is only available for patients with breast and lung cancer and melanoma. Overall, targeted approaches approximately doubled the lifespan in the subgroups of brain metastases from tumors with targetable surface receptors such as anaplastic lymphoma kinase (ALK) fusion receptor in non-small cell lung cancer or human epidermal growth factor receptor 2 (HER2)-positive breast cancer. For these types, overall survival in the situation of brain metastases is now more than a year. For receptor-negative lung cancer and melanoma, introduction of immune checkpoint blockers brought a substantial advance, although overall survival for melanoma metastasized to the brain appears to remain in the range of 6 to 9 months. The outlook for small cell lung cancer metastasized to the brain apparently remains poor. The introduction of targeted therapy roughly doubled survival times of advanced cancers including those metastasized to the brain, but so far, targeted therapy does not differ essentially from chemotherapy, therefore also facing tumors developing escape mechanisms. With the improved perspective of patients suffering from brain metastases, it becomes important to further optimize treatment of this specific patient group within the framework of randomized trials.