Assessment of Local and Regional Control in Atypical (WHO Grade 2) Meningiomas Receiving Fractioned Stereotactic Radiotherapy

PURPOSE/OBJECTIVE(S)

The optimal delivery of postoperative radiotherapy to WHO grade 2 or atypical meningiomas (AM) is controversial. The historical standard of care has been high dose fractionated radiation to the resection bed and a 2 cm CTV as in RTOG 0539. Single fraction radiosurgery offers a more conformal alternative with demonstrated local control for smaller AM in less sensitive areas. Though less studied, fractionated stereotactic radiosurgery (FSRT) promises safer treatment of larger AM in more sensitive locations while minimizing the treated volume. This single institution retrospective review examines the hypothesis that local and marginal failure patterns in AM treated with five fraction FSRT remain unacceptably high.

MATERIALS/METHODS

Thirty-nine patients received 27.5 - 30 Gy in 5 fractions to their AM from 2009 to 2022 with grading based on the WHO criteria active at the time of treatment. All treatments were frameless VMAT deliveries with no PTV margin. Histological diagnosis of AM, gross disease at time of FSRT, five fraction FSRT, and lack of prior local radiation were required for inclusion. Single fraction treatments were excluded. Local recurrence was defined similar to RECIST criteria as an increase of 20% in the greatest cross-sectional diameter on MRI (or CT if MRI contraindicated) with at least one voxel touching the prescription volume. To examine the role of CTV margin, marginal recurrence was defined as any new lesion outside of the prescription volume but within 2 cm of the resection cavity. High grade toxicity per CTCAE v5 was an irreversible grade 3 or any grade 4 toxicity. Resection for radionecrosis was considered a local failure if any viable tumor was seen on pathology.

RESULTS

Median follow up was 32.5 months (range 3.2-147.5 months). The number of AM treated post STR, post GTR recurrence, and definitively were 26, 16, and 5 respectively. 3-year local tumor control was estimated to be 84%. As expected, larger tumors were more likely to fail locally (p >.001). Two (5%) patients experienced high grade toxicity - both symptomatic radionecrosis requiring resection. Three-year marginal control was estimated to be 92.3%. Of the 5 tumors treated to the entire resection cavity, none experienced a marginal failure. Interestingly, recurrent tumors s/p GTR were more likely to recur marginally than tumors treated after STR (p = .009). Only 1 (4%) tumor treated after STR failed marginally while 4 (33%) tumors treated after GTR recurrence failed.

CONCLUSION

The rate of high-grade toxicity in AM receiving FSRT was low. Local control appeared comparable to historical rates which may suggest the need for dose escalation with longer term follow-up. Recurrent tumors appear more prone to marginal failures, however more work is needed to determine which patients may benefit from additional CTV margin and more prolonged fractionated dose schedules. Improved targeting with newer imaging studies (e.g., DOTATATE PET) should be examined to determine if more accurate targeting will improve outcomes.

Frameless LINAC-Based Stereotactic Radiosurgery is Safe and Effective for Essential and Parkinsonian Tremor

PURPOSE/OBJECTIVE(S)

Stereotactic radiosurgery (SRS) to the thalamus is an ablative technique used for treatment of refractory tremor of essential or Parkinsonian origin. Because of the high dose, small target, and required precision, framed SRS on the Gamma Knife has been the historical platform of choice. We tested our recently developed technique to emulate GK dose distributions on a multi-leaf collimator (MLC)-equipped linear accelerator (LINAC) without cumbersome, inefficient cones in a prospective trial of safety and efficacy.

MATERIALS/METHODS

We quantified pre-treatment contralateral tremor according to FTM scoring system. We obtained MPRAGE, FGATIR, DTI, and RS-fMRI sequences. We identified the VIM via classical stereotactic reference location and connectomically, and then targeted it to 135 Gy dmax in a manner dosimetrically roughly equivalent to 4 mm GK shot. We adjusted each target such that the 25 Gy isodose line did not overlap the posterior limb of the capsule. We immobilized patients in a highly rigid thermoplastic mask and delivered treatment on an Edge™ LINAC with HDMLC. Intrafraction optical surface monitoring (OSMS) ensured patient immobility. We surveilled post-treatment imaging and recorded tremor scoring, QOL outcomes, and adverse events.

RESULTS

We accrued 42 patients (16 female, 26 males; median age 72.5) over 36 months. 38 had essential tremor, 4 had tremor-dominant Parkinson's; 2 withdrew prior to treatment. Ten patients were on therapeutic anti-coagulation, and were not required to discontinue. At time of submission 39 patients had follow-up ≥ 6 months. 35/39 (89.7%) exhibited clinically meaningful tremor reduction. Mean limb tremor reduction among responders was 43.5% (range: 9 - 100%). Time to patient-reported tremor improvement was 0.3 to 15 months. One patient experienced Gr 3, and 4 patients experienced Gr 1-2 toxicity.

CONCLUSION

MLC-based SRS thalamotomy is safe and effective for refractory tremor treatment. Multidisciplinary management is key for proper patient selection, treatment, and monitoring. Our outcomes appear congruent to historical GK controls as well as more modern MRgFUS outcomes.

Early Clinical Experience of Utilizing Online Adaptive Radiotherapy for Accelerated Partial Breast Irradiation with Stereotactic Body Radiation Therapy for Early-Stage Breast Cancer Patients

PURPOSE/OBJECTIVE(S)

Accelerated partial breast irradiation (APBI) with stereotactic body radiation therapy (SBRT) is becoming popular for early-stage breast cancer (ESBC) due to decreased treatment time and dose to healthy breast tissue. With variability in lumpectomy cavity size post-surgery, CBCT-guided online adaptive RT (oART) may improve target coverage and reduce normal tissue exposure by accounting for inter- and intrafractional cavity variations. In this study, we report our initial clinical experience utilizing APBI oART for patients with ESBC.

MATERIALS/METHODS

A total of 15 patients with 17 ESBC cavities (2 with bilateral disease) were treated with SBRT using oART over one year. Patients were immobilized using standard breast simulation setup with free breathing and breath hold (if left sided). The clinical target volume consisted of an isometric 1 cm expansion off the lumpectomy cavity, which was expanded another 3 mm (cropped 3mm from surface) to create the planning target volume (PTV). 95% of the PTV received prescription dose (30 Gy in 5 fractions). The oART delivery process (supervised by physician and physicist) initially coregisters the daily CBCT to the treatment planning CT with alignment to lumpectomy cavity. Target volumes and organs-at-risk were modified at each treatment and the plan re-optimized. Either the re-optimized oART plan or scheduled plan was chosen for each fraction pending which plan best met prespecified clinical goals. Acute toxicity was assessed at one-month follow-up using CTCAE.

RESULTS

Patients were age 56 or older, ECOG 0-1, with no known genetic abnormality, and with anatomic stage 0-1A ESBC. Most tumors were located in the upper outer quadrant (n = 12, 70.6%) at middle or posterior depth (n = 15, 88.2%). Final margins were negative. 88% had tantalum clips placed. One patient had an Oncotype DS score of 34 and received systemic therapy. 82.3% met suitable APBI criteria and 3 met cautionary criteria due to high grade, of which 2 had ipsilateral trimodality treatment 10+ years prior and denied mastectomy at recurrence. Mean time to starting RT after lumpectomy was 2.5 months. Mean PTV to breast ratio was 0.12. From simulation to end of treatment, lumpectomy cavity size decreased a median of 27%. oART plans were chosen 89% of the time. VMAT was utilized 52.9% of the time compared to static-field IMRT (47.1%). Three patients were treated with breath hold. 93% of patients were treated on non-consecutive days with average treatment lasting 9.1 ± 2.2 days. CTCAE grade 1 toxicities were hyperpigmentation (n = 6, 40%), breast pain (n = 2, 13.3%), persistent seroma (n = 1, 6.7%), and fatigue (n = 7, 46.7%). No patients experienced fat necrosis, telangiectasias, breast shrinkage, lymphedema, or CTCAE grade 2+ toxicities.

CONCLUSION

oART for APBI using SBRT for patients with ESBC is clinically feasible and allows for variations in lumpectomy cavity size. Nearly half of patients had no complaints or breast changes at one-month follow-up and the remaining had CTCAE grade 1 toxicities alone.

Connectomic Basis for Tremor Control in Stereotactic Radiosurgical Thalamotomy

BACKGROUND AND PURPOSE

Given the increased use of stereotactic radiosurgical thalamotomy and other ablative therapies for tremor, new biomarkers are needed to improve outcomes. Using resting-state fMRI and MR tractography, we hypothesized that a "connectome fingerprint" can predict tremor outcomes and potentially serve as a targeting biomarker for stereotactic radiosurgical thalamotomy.

MATERIALS AND METHODS

We evaluated 27 patients who underwent unilateral stereotactic radiosurgical thalamotomy for essential tremor or tremor-predominant Parkinson disease. Percentage postoperative improvement in the contralateral limb Fahn-Tolosa-Marin Clinical Tremor Rating Scale (TRS) was the primary end point. Connectome-style resting-state fMRI and MR tractography were performed before stereotactic radiosurgery. Using the final lesion volume as a seed, "connectivity fingerprints" representing ideal connectivity maps were generated as whole-brain R-maps using a voxelwise nonparametric Spearman correlation. A leave-one-out cross-validation was performed using the generated R-maps.

RESULTS

The mean improvement in the contralateral tremor score was 55.1% (SD, 38.9%) at a mean follow-up of 10.0 (SD, 5.0) months. Structural connectivity correlated with contralateral TRS improvement (r = 0.52; P  = .006) and explained 27.0% of the variance in outcome. Functional connectivity correlated with contralateral TRS improvement (r = 0.50; P  = .008) and explained 25.0% of the variance in outcome. Nodes most correlated with tremor improvement corresponded to areas of known network dysfunction in tremor, including the cerebello-thalamo-cortical pathway and the primary and extrastriate visual cortices.

CONCLUSIONS

Stereotactic radiosurgical targets with a distinct connectivity profile predict improvement in tremor after treatment. Such connectomic fingerprints show promise for developing patient-specific biomarkers to guide therapy with stereotactic radiosurgical thalamotomy.

Role of IκBα as a negative regulator of EGFR and a molecular determinant of prognosis in glioblastoma multiforme

2028

Background: Glioblastoma multiforme is a complex disease that involves the deregulation of overlapping signaling pathways. Constitutive activation of the transcription factor nuclear factor-κB (NF-κB) has been broadly associated with various human cancers, including glioblastomas, and their therapy resistance and may be due to cross-coupling with other oncogenic pathways, such as epidermal growth factor signaling. Methods: Multidimensional analysis involving gene and transcript data for the endogenous NF-κB modulator IκBα/NFKBIA and clinical patient profiles of 482 glioblastomas/high-grade gliomas from multiple institutions in the United States and The Cancer Genome Atlas Pilot Project. Functional analyses using LN229, U87, and U118 glioblastoma cells, and human embryonic kidney 293T cells with transgene phenotypes for IκBα. IκBα promoter and coding sequence and promoter methylation analyses in a resistance model of 15 glioblastomas cell lines with in vitro and/or in vivo resistance to O6-alkylating agents. Results: We have identified a regulatory circuit between NF-κB and EGFR signaling in glioblastomas, where IκBα binds to EGFR and attenuates EGFR signaling by immobilizing its kinase domain into an inactive conformation. We found the NFKBIA gene at 14q13.2 deleted in 25% of glioblastomas and its occurrence mutually exclusive with EGFR amplification. Loss of NFKBIA associates independently with patient survival. Functional analyses uncover a bona fide tumor suppressor role for IκBα in glioblastoma cells, where it functions to constrain tumorigenic and migratory potential, and induce spontaneous cellular senescence, and apoptosis in response to treatment. IκBα expression is an independent predictor of patient prognosis in multiple glioblastoma populations. Glioblastomas with initially high IκBα expression significantly repress IκBα upon tumor recurrence, suggesting an acquired mechanism to evade its tumor-suppressive and/or chemo-sensitizing effects during tumor progression. Conclusions: IκBα is a molecular determinant of biological tumor behavior and patient survival in glioblastoma multiforme. Deletion of NFKBIA could present an alternate mechanism to activate EGFR signaling in EGFR non-amplified glioblastomas.

No significant financial relationships to disclose.

A regulatory network of canonical nuclear factor-κB activation predicts high-grade glioma outcome

2007

Background: The mechanism for decision between cell death and survival is under fine regulation. Nuclear factor-κB is a transcription regulator that is known to promote survival in many cellular events. Excessive and prolonged activation of NF-κB has been established as a principal mechanism of tumor chemoresistance, which is primarily mediated by its antiapoptotic activity. The pathway leading to the activation of NF-κB involves a complicated network that includes multiple modulatory signaling molecules. We have discovered alterations in several NF-κB pathway modulators in glioblastoma cells, which may act synergistically in activating NF-κB during resistance formation to O6-alkylating agents, including the TNFAIP3, NFKBIA, and TNIP1 genes. Methods: We have retrospectively evaluated the outcome relationship for these and additional endogenous inhibitors of canonical NF-κB activation in three independent high-grade glioma cohorts comprising 175 tumors. Results: We here confirmed the putative importance of NF-κB pathway activation status in predicting high-grade glioma outcome. Our data indicate an increasing complexity and linkage of several modulatory molecules (TNFAIP3, NFKBIA, TNIP1, and TNIP2) to patient outcome that interact physical and functionally in a cooperative fashion to regulate NF-κB activation. We found that for many of these molecules combined predictor models outperform the predictive power of the individual molecules. This observation is consistent with recent evidence suggesting the cooperation of these endogenous inhibitors in a negative feedback regulation of NF-κB activation and a mutual facilitation of their repressive ability. In terms of outcome prediction, we found several of these inhibitors to outperform established clinical and morphological prognostic variables such as patient age and tumor grade (III vs. IV), as well as the O6-methylguanine DNA methyltransferase (MGMT) gene, the currently most established outcome marker in glioblastomas. Conclusions: These findings raise the hope for this regulatory network as an amenable target to modulate NF-κB-mediated resistance in glioblastoma cells, with the ultimate goal of increasing the efficacy of chemotherapy in patients harboring these challenging tumors.

No significant financial relationships to disclose.

Tumor necrosis factor-α-induced protein 3 down-regulates nuclear factor-κB-mediated drug resistance in vitro and is a favorable clinical prognostic factor in human glioblastomas

1508

Background: Resistance to chemotherapy is major impediment to the successful treatment of human glioblastomas. Methods: We used an integrated resistance model and genomics tools to globally explore molecular factors and cellular pathways mediating resistance to O6-alkylating agents in glioblastoma cells. Results: We identified a transcriptomic signature of 286 genes that predicts a common in vitro and in vivo resistance phenotype to these agents. This signature was significantly enriched for genes with functions in organismal survival (27.5%) and cell death (49.0%), both with P < 0.00001. Modularity was a predominant organizational principle of the signature, with functions being carried out by groups of interacting molecules in overlapping networks. A highly significant network was built around nuclear factor-κB (NF-κB), which included the persistent alterations of various NF-κB pathway elements. Tumor necrosis factor-α-induced protein 3 (TNFAIP3) was identified as a new endogenous regulatory component of a putative cytoplasmic signaling cascade that mediates NF-κB activation in response to DNA damage caused by O6-alkylating agents. Expression of the corresponding zinc finger protein A20 closely mirrored the expression of the TNFAIP3 transcript, and was inversely related to NF-κB activation status in the resistant cells. A prediction model based on the resistance signature enabled the subclassification of an independent, validation cohort of 31 glioblastomas into two outcome groups (P = .037). TNFAIP3 expression was a favorable factor in patient prognosis (P = .028), and was part of an optimized four-gene predictor (TNFAIP3, CD44 antigen, syndecan 1, and F-box protein 32) significantly associated with patient survival (P = .022). Conclusions: Our results offer strong evidence for TNFAIP3 as a key regulator of the cytoplasmic signaling to activate NF-κB en route to O6-alkylating agent resistance in glioblastoma cells. This gene may be an attractive target for therapeutic modulation of glioblastomas.

No significant financial relationships to disclose.

DNA topoisomerase IIalpha expression in optic pathway gliomas of childhood

DNA topoisomerase IIalpha (Topo IIalpha) is linked to tumour cell growth and chemoresistance. We examined immunohistochemically Topo IIalpha expression levels in a series of 36 consecutive paediatric optic pathway glioma (OPG) patients. Topo IIalpha labelling index (LI) ranged from 0.0 to 11.6 and was significantly associated with patient age, with higher levels of Topo IIalpha in children < or = 3 years (P=0.031). Topo IIalpha expression did not correlate with patient survival. Topo IIalpha LI was not significantly increased in specimens of repeat surgery. Topo IIalpha LI closely correlated with MIB-1 LI (R=0.781, P<0.001). We conclude that Topo IIalpha expression correlates with tumour cell proliferation in paediatric OPGs. Assessment of cell proliferation, however, does not assist in refining prognostic predictions. Enhanced Topo IIalpha expression in children < or = 3.0 years suggests that Topo IIalpha-interfering anticancer compounds for adjuvant treatment of OPGs may be of particular benefit to young children.

Anticancer drug resistance in primary human brain tumors

The difficult clinical situation still associated with most types of primary human brain tumors has fostered significant interest in defining novel therapeutic modalities for this heterogeneous group of neoplasms. Beginning in the 1980s chemotherapy has been incorporated into the treatment protocol of a number of intractable brain tumors. However, it has predominantly failed to improve patient outcome. The unsatisfactory results with chemotherapeutic intervention have chiefly been attributed to tumor cell resistance. In recent years, there has been a literal explosion in our understanding about the mechanisms by which cancer cells become chemoresistant. During the course of their evolution (intrinsic resistance) or in response to chemotherapy (acquired resistance) these cells may follow a number of pathways of genetic alterations to possess a common (multidrug) or drug-specific (individual drug) resistant phenotype. Genomic aberrations, deregulation of membrane transporting proteins and cellular enzymes, and an altered susceptibility to commit to apoptosis are among the steps on the way that contribute to the genesis of chemotherapeutic treatment failure. Although, through the years we have come to yield information and inferences as to the roles that different molecular events may have in the resistance phenotype of cancer cells, the actual involvement of single genetic alterations in conferring drug resistance in primary brain tumors remains debatable. This uncertainty and, besides, the lack of proper drug resistance diagnostics, in a vicious circle, hinder the development of effective resistance-modulation strategies. Clinical non-responsiveness to chemotherapy remains a formidable obstacle to the successful treatment of brain tumors and one of the most serious problems to be solved in the therapy of these lesions. Future advances in the chemotherapeutic management of these neoplasms will come with an improved understanding of the significance and interrelationship of the multiple biological systems operative in promoting resistance to this treatment modality. The focus of this review is to summarize current knowledge concerning major drug resistance-related markers, to describe their functional interaction en route to chemoresistance, and to discuss their implication in rendering human brain tumor cells resistant to chemotherapy.

Inhibition of Ras and related guanosine triphosphate-dependent proteins as a therapeutic strategy for blocking malignant glioma growth: II--preclinical studies in a nude mouse model

OBJECTIVE

Preliminary studies have demonstrated that the Ras family and related guanosine triphosphate-dependent proteins are overactivated in malignant gliomas and that inhibition of the activation of such proteins, by blockade of their post-translational processing, reduces tumor cell growth in vitro. The current study evaluates the utility of this therapeutic strategy in vivo, using preclinical glioma model systems.

METHODS

We examined the efficacy against U-87 human malignant glioma cells, in both subcutaneous and intracranial nude mouse models, of selective peptidomimetic inhibitors of farnesyltransferase (FTI-276) and geranylgeranyltransferase (GGTI-297), which are involved in critical steps in the post-translational processing of Ras and related guanosine triphosphate-dependent proteins. For the subcutaneous model, 2 x 10(5) U-87 cells were implanted; after measurable tumors were detected on Day 7, animals were treated with either FTI-276, GGTI-297, or vehicle, administered by continuous infusion for 7 days. Differences in tumor volumes among the treatment groups were examined for significance using a Student's t test. For the intracranial model, 2 x 10(5) U-87 cells were implanted in the right frontal lobe and treatment was initiated on Day 7. In initial studies, animals received a 7-day course of either FTI-276, GGTI-297, or vehicle. In subsequent studies, a 28-day treatment period was used. Comparisons of survival times among treatment groups were performed using a rank-sum test.

RESULTS

Although the two agents exhibited comparable antiproliferative activities in previous in vitro studies, an obvious difference in efficacy was apparent in this study. Whereas the geranylgeranyltransferase inhibitor failed to improve survival rates, compared with those observed for control animals, in either the subcutaneous or intracranial model, the farnesyltransferase inhibitor produced objective regression of tumor growth in the subcutaneous model and significant prolongation of survival times in the intracranial model, without apparent toxicity. In the subcutaneous model, tumor volumes for the control, GGTI-297-treated, and FTI-276-treated animals on Day 28 after implantation were 621+/-420, 107+/-104, and 18.5+/-12.7 mm3, respectively (P < 0.05). In the 7-day-treated intracranial model, survival times for the control, GGTI-297-treated, and FTI-276-treated groups were 27.7+/-2.9, 29.8+/-2.1, and 43.6+/-2.7 days, respectively (P < 0.001). In the 28-day-treated intracranial model, survival times for the control, GGTI-297-treated, and FTI-276-treated groups were 29.2+/-3.7, 28.3+/-3.9, and 58.7+/-6.2 days, respectively, with five of six animals in the latter group surviving more than 55 days after tumor implantation (P < 0.001).

CONCLUSION

These studies demonstrate that farnesyltransferase inhibition is effective in diminishing the growth of human glioma cells in vivo. Evaluation of this treatment approach in clinical trials is warranted.

Epidermal growth factor receptor expression and gene amplification in high-grade non-brainstem gliomas of childhood

Epidermal growth factor receptor (EGFR) is commonly overexpressed in adult high-grade gliomas. Forty to 50% of such tumors demonstrate amplification of the EGFR gene, often with rearrangement and constitutive activation of the gene product, suggesting that EGFR might play a role in the malignant progression of a subset of these neoplasms. In this regard, several groups have shown that overexpression of EGFR is associated with an adverse outcome in adult gliomas. In contrast to the extensive studies of EGFR status that have been performed in adult high-grade gliomas, little information has been reported about EGFR expression and amplification, as well as their prognostic relevance in high-grade gliomas of childhood, which carry a somewhat more favorable prognosis than their adult counterparts. To address this issue, we examined the expression of EGFR using immunohistochemistry and screened for amplification of the EGFR gene using a competitive PCR in a series of 27 archival pediatric high-grade nonbrainstem gliomas treated consecutively at our institution between 1975 and 1992. Tumors were categorized based on protein expression patterns, and the association between expression status and outcome was examined. Although elevated immunoreactivity for EGFR was observed in 80% of tumors, only two of the cases had gene amplification. No difference in outcome was observed between tumors that exhibited extensive EGFR immunoreactivity and those that did not (P > 0.3). Although EGFR expression did not seem to be of prognostic relevance for the outcome of pediatric patients harboring high-grade nonbrainstem gliomas, the consistently high levels of expression of EGFR in these neoplasms suggest that this receptor plays a role in the malignant phenotype of these tumors. Accordingly, treatment approaches targeting EGFR might be of potential therapeutic benefit for high-grade gliomas of childhood.

The p21-Ras signal transduction pathway and growth regulation in human high-grade gliomas

Deregulated p21-Ras function, as a result of mutation, overexpression or growth factor-induced overactivation, contributes to at least 30% of human cancer. This article reviews the potential role of the p21-Ras family of GTPases in the regulation of growth of high-grade gliomas and describes how targeting this oncoprotein clinically may provide a novel strategy to counteract glioma proliferation. The application of strategies directed at selectively opposing the deregulated signal transduction pathway of high-grade gliomas may be of potential therapeutic benefit and may offer a whole new arsenal of antineoplastic agents to be included in the multimodal treatment of these challenging neoplasms.