Cost-Effectiveness Analysis of 68Ga-DOTATATE PET/MRI in Radiotherapy Planning in Patients with Intermediate-Risk Meningioma

BACKGROUND AND PURPOSE

While contrast-enhanced MR imaging is the criterion standard in meningioma diagnosis and treatment response assessment, gallium 68Ga-DOTATATE PET/MR imaging has increasingly demonstrated utility in meningioma diagnosis and management. Integrating 68Ga-DOTATATE PET/MR imaging in postsurgical radiation planning reduces the planning target volume and organ-at-risk dose. However, 68Ga-DOTATATE PET/MR imaging is not widely implemented in clinical practice due to higher perceived costs. Our study analyzes the cost-effectiveness of 68Ga-DOTATATE PET/MR imaging for postresection radiation therapy planning in patients with intermediate-risk meningioma.

MATERIALS AND METHODS

We developed a decision-analytical model based on both recommended guidelines on meningioma management and our institutional experience. Markov models were implemented to estimate quality-adjusted life-years (QALY). Cost-effectiveness analyses with willingness-to-pay thresholds of $50,000/QALY and $100,000/QALY were performed from a societal perspective. Sensitivity analyses were conducted to validate the results. Model input values were based on published literature.

RESULTS

The cost-effectiveness results demonstrated that 68Ga-DOTATATE PET/MR imaging yields higher QALY (5.47 versus 5.05) at a higher cost ($404,260 versus $395,535) compared with MR imaging alone. The incremental cost-effectiveness ratio analysis determined that 68Ga-DOTATATE PET/MR imaging is cost-effective at a willingness to pay of $50,000/QALY and $100,000/QALY. Furthermore, sensitivity analyses showed that 68Ga-DOTATATE PET/MR imaging is cost-effective at $50,000/QALY ($100,000/QALY) for specificity and sensitivity values above 76% (58%) and 53% (44%), respectively.

CONCLUSIONS

68Ga-DOTATATE PET/MR imaging as an adjunct imaging technique is cost-effective in postoperative treatment planning in patients with meningiomas. Most important, the model results show that the sensitivity and specificity cost-effective thresholds of 68Ga-DOTATATE PET/MR imaging could be attained in clinical practice.

Hypofractionated Postoperative Radiotherapy for Prostate Cancer: Is the Field Ready Yet?

Context

Radiotherapy (RT) is a valid adjuvant treatment for men with high-risk pathological features after radical prostatectomy and a salvage treatment for biochemical recurrence. A major inconvenience is that RT takes course over 7–8 wk in these settings, which has been shown to limit its use. Retrospective and pilot prospective investigations suggest that hypofractionation may provide noninferior outcomes but report variable results regarding toxicities. Additionally, our evolving understanding of prostate cancer radiobiology suggests that hypofractionated regimens may not increase toxicity.

Objective

We examine and review the rationale and clinical evidence of hypofractionated RT in the adjuvant and salvage settings for prostate cancer.

Evidence acquisition

We reviewed relevant literature, with a particular focus on recent studies employing hypofractionated RT.

Evidence synthesis

Hypofractionated RT in the adjuvant or salvage setting is not a standard option for prostate cancer RT outside of an investigational trial. While smaller studies show conflicting data regarding toxicity, initial evidence from larger clinical trials appears to demonstrate that hypofractionated postoperative RT is as effective and safe as conventionally fractionated courses.

Conclusions

With the growing acceptance of hypofractionation across other cancer sites and the rise of extreme hypofractionation for definitive prostate cancer treatment, hypofractionated postoperative therapy for prostate cancer is poised to become an option, as it may reduce the burden on men and treatment centers while maintaining clinical efficacy and safety. Prospective trials are currently ongoing to address efficacy and safety concerns.

Patient summary

Postoperative radiotherapy is a potentially curative treatment for patients with high-risk disease or recurrence after surgery. Shortening of the treatment regimen with the availability of modern treatment delivery techniques in conjunction with the integration of molecular imaging information to refine treatment volumes may improve therapeutic benefit without increasing toxicity.

45. DELAY OR FAILURE TO ADMINISTER STEREOTACTIC RADIOSURGERY TO THE CAVITY AFTER SURGERY FOR BRAIN METASTASES. AN INTENTION-TO-TREAT ANALYSIS

BACKGROUND

Data regarding the efficacy of adjuvant stereotactic radiosurgery (SRS) for resected brain metastases (BM) is often limited to patients completing SRS within a specified timeframe. We performed an intention-to-treat analysis to determine local recurrence (LR) for all BM patients referred for SRS.

METHODS

We retrospectively identified resected BM patients referred for SRS between 2012 and 2018. Patients were divided based on delay to SRS into four categories: 1) ≤4 weeks, 2) >4–8 weeks, 3) >8 weeks, and 4) never received. We investigated the relationship between delay to SRS and LR, local recurrence-free survival (LRFS), and overall survival, as well as the predictors of and reason for delays.

RESULTS

In our cohort of 159 patients, median age was 64.0 years, 56.5% patients were female, median tumor diameter was 2.9 cm, and gross total resection was achieved in 83.0%. On intention-to-treat analysis, LR was 22.6%. Delays to SRS correlated with LR: 2.3% with SRS ≤4 weeks postoperatively, 14.5% with SRS at >4–8 weeks (p=0.03), 48.5% with SRS at >8 weeks (p<0.001). No LR difference was observed with SRS delayed by >8 weeks, vs. never completed, 48.5% vs. 50.0% (p=0.91). 53 (33.3%) patients comprised these latter two categories. A similar relationship emerged between delay to SRS and LRFS (p<0.01). Non-small cell lung cancer pathology (p=0.04) and earlier year of treatment (p<0.01) were predictive of delays. Common reasons for delays included logistics, management of systemic disease, complications, or comorbidities.

CONCLUSION

A significant number of patients referred for SRS never receive it, or are treated with a delay >8 weeks, conferring equivalent LR risk. Accordingly, the actual efficacy of adjuvant SRS may need reassessment. Reasons for delays and mechanisms for reducing them are discussed. For patients likely to experience significant delays, other techniques, such as preoperative SRS or intraoperative brachytherapy, may be considered.

43. DELAYS IN ADJUVANT STEREOTACTIC RADIOSURGERY REDUCE LOCAL CONTROL FOR RESECTED BRAIN METASTASES

OBJECTIVE

For resected brain metastases (BM), stereotactic radiosurgery (SRS) is often offered to minimize local recurrence (LR). Although the aim is to deliver SRS within a few weeks of surgery, a variety of socioeconomic, medical, and procedural issues can cause delays. We evaluated the relationship between timing of postoperative SRS and LR.

METHODS

We retrospectively identified a consecutive series of BM patients managed with resection and adjuvant SRS, recommended within two weeks of surgery, at our institution from 2012–2018. We assessed the correlation between time to SRS, as well as other demographic, disease, and treatment variables, and LR, distant recurrence (DR), and overall survival (OS).

RESULTS

133 patients met inclusion criteria. Median age was 64.5 years. Approximately half of patients had a single BM, and median BM size was 2.9 cm. Gross total resection was achieved in 111 (83.6%) patients, and >90% received fractionated SRS. Median time to adjuvant SRS was 37.0 days and LR rate was 16.4%. The factor most predictive of LR was time from surgery to SRS. Median time from surgery to SRS was 34.0 days for patients without LR, versus 61.0 days for those with LR (p<0.01). LR was 2.3% with SRS administered ≤4 weeks postoperatively, compared to 23.6% if delayed >4 weeks (p<0.01). Local recurrence-free survival (LRFS) was also improved for patients who had SRS at ≤4 weeks (p=0.02). Delayed SRS was also predictive of DR (p=0.02), but not OS.

CONCLUSIONS

We demonstrate that the strongest predictor of failure of postoperative SRS for BM is the delay to SRS. A cut-off of 4 weeks is a reliable predictor of increased LR. Every effort should be made to perform SRS within 4 weeks of surgery, and if this cannot be achieved, other RT modalities, such as brachytherapy or preoperative SRS, should be strongly considered.

RADI-26. DOSIMETRIC EVALUATION OF 6 MV VERSUS 10 MV PHOTONS FOR HIPPOCAMPAL AVOIDANCE WHOLE BRAIN RADIOTHERAPY

OBJECTIVE: Whole brain radiotherapy (WBRT) causes neurocognitive decline. Hippocampal avoidance WBRT (HA-WBRT) reduces hippocampal irradiation, potentially mitigating neurocognitive sequelae. We compared hippocampal and brain dosimetry with HA-WBRT with 6 megavoltage (MV) versus 10 MV photon energies. METHODS: Twenty consecutive patients treated with WBRT were retrospectively replanned with HA-WBRT techniques using 6 MV and 10 MV photons. Coplanar volumetric modulated arc therapy was employed, with a prescription dose of 3000 cGy in 10 fractions. Planning was done with Eclipse version 13.6 or 15.6. Nine patients were planned with 2.5 mm multileaf collimator leaves, with the remainder planned with 5 mm leaves. The hippocampi were contoured and a HA structure was generated using a uniform 5 mm expansion. A planning target volume (PTV) was defined as the brain parenchyma minus the HA structure. NRG-CC001 dose constraints were used. For each variable, descriptive statistics were calculated. Comparisons were made using two-tailed Wilcoxon signed rank tests or paired t-tests. RESULTS: The minimum hippocampal dose (D100%) was improved with 6 MV plans, 841 cGy compared to 914 cGy with 10 MV (p< 0.005). The maximum hippocampal dose (D0.03cc) was reduced with 6 MV planning, 1614 cGy versus 1676 cGy for 10 MV (p< 0.0001). With 6 MV photons, a greater number of plans met NRG-CC001 constraints without deviations. 6 MV photons improved PTV coverage by the 95% isodose line, 96.6% compared to 95.9% for 10 MV (p=0.021). 6 MV photon plans decreased the volume of PTV receiving ≥105% of the prescription, 84.2% versus 87.9% for 10 MV (p=0.006). The mean dose, hot spots, and cold spots did not differ by photon energy. PTV dose constraints were always met. CONCLUSION: 6 MV photon HA-WBRT plans are dosimetrically superior to 10 MV, reducing hippocampal radiation dose, without compromise in brain coverage and improved target dose homogeneity.

Survival Disparities in the Radiotherapeutic Management of Lung Cancer by Regional Poverty Level

Purpose

This study evaluates regional poverty level-dependent differences in lung cancer (LC) survival, focusing on patients receiving radiation therapy (RT).

Methods and materials

The Surveillance, Epidemiology, and End Results (SEER) database was used to retrospectively identify patients diagnosed with LC between 2000 and 2009. Patients were divided into socioeconomic status (SES) quintiles, with quintiles 1 and 5 representing the highest and lowest SES cohorts, respectively. The Kaplan-Meier method with the log-rank test was used to compare overall survival (OS) from diagnosis between demographic and clinical factor levels. Multivariate (MVA) Cox proportional hazards regression was used to examine the association of quintile and mortality, adjusting for demographic and clinical factors.

Results

Compared to those not receiving RT, the univariate (UVA) results showed a higher mortality associated with receiving RT (HR:1.091; CI:1.081-1.102) while the MVA demonstrated a protective effect (HR:0.882; CI:0.873-0.891). The MVA revealed that men had higher mortality rates than women (HR:1.192; CI:1.180-1.203). Caucasians had a lower mortality rate as compared to African Americans (adjusted HR:0.932; CI:0.918-0.947) while Asians, Pacific Islanders, and Native Americans had the highest overall survival rates (adjusted HR:0.752, CI:0.734-0.771). Among the entire study population, quintile 2 (HR:1.059, CI:1.043-1.076), quintile 3 (HR:1.091, CI:1.075-1.108), quintile 4 (HR:1.094, CI:1079-1.110), and quintile 5 (HR:1.201, CI:1.181-1.221) reported increased mortality rates compared with quintile 1. This trend was also observed among those undergoing RT, with quintile 2 (HR:1.034, CI:1.010-1.059), quintile 3 (HR:1.045; CI:1.021-1.069), quintile 4 (HR:1.056; CI:1.033-1.080), and quintile 5 (HR:1.153; CI:1.124-1.183) demonstrating incrementally worse OS.

Conclusions

Upon accounting for age, gender, race, SES, and tumor stage, RT may provide a positive survival benefit among those who received treatment. Minimal differences existed among SES quintiles regarding diagnoses made by tumor stage or patients receiving RT. An incrementally worse OS rate was associated with increasing regional poverty level. This trend persevered among those receiving RT.

Hypoxia-Mediated Mechanisms Associated with Antiangiogenic Treatment Resistance in Glioblastomas

Glioblastomas (GBMs) are malignant tumors characterized by their vascularity and invasive capabilities. Antiangiogenic therapy (AAT) is a treatment option that targets GBM-associated vasculature to mitigate the growth of GBMs. However, AAT demonstrates transient effects because many patients eventually develop resistance to this treatment. Several recent studies attempt to explain the molecular and biochemical basis of resistance to AAT in GBM patients. Experimental investigations suggest that the induction of extensive intratumoral hypoxia plays a key role in GBM escape from AAT. In this review, we examine AAT resistance in GBMs, with an emphasis on six potential hypoxia-mediated mechanisms: enhanced invasion and migration, including increased expression of matrix metalloproteinases and activation of the c-MET tyrosine kinase pathway; shifts in cellular metabolism, including up-regulation of hypoxia inducible factor-1α's downstream processes and the Warburg effect; induction of autophagy; augmentation of GBM stem cell self-renewal; possible implications of GBM-endothelial cell transdifferentiation; and vasoformative responses, including vasculogenesis, alternative angiogenic pathways, and vascular mimicry. Juxtaposing recent studies on well-established resistance pathways with that of emerging mechanisms highlights the overall complexity of GBM treatment resistance while also providing direction for further investigation.

Combinatorial actions of Tgfβ and Activin ligands promote oligodendrocyte development and CNS myelination

In the embryonic CNS, development of myelin-forming oligodendrocytes is limited by bone morphogenetic proteins, which constitute one arm of the transforming growth factor-β (Tgfβ) family and signal canonically via Smads 1/5/8. Tgfβ ligands and Activins comprise the other arm and signal via Smads 2/3, but their roles in oligodendrocyte development are incompletely characterized. Here, we report that Tgfβ ligands and activin B (ActB) act in concert in the mammalian spinal cord to promote oligodendrocyte generation and myelination. In mouse neural tube, newly specified oligodendrocyte progenitors (OLPs) are first exposed to Tgfβ ligands in isolation, then later in combination with ActB during maturation. In primary OLP cultures, Tgfβ1 and ActB differentially activate canonical Smad3 and non-canonical MAP kinase signaling. Both ligands enhance viability, and Tgfβ1 promotes proliferation while ActB supports maturation. Importantly, co-treatment strongly activates both signaling pathways, producing an additive effect on viability and enhancing both proliferation and differentiation such that mature oligodendrocyte numbers are substantially increased. Co-treatment promotes myelination in OLP-neuron co-cultures, and maturing oligodendrocytes in spinal cord white matter display strong Smad3 and MAP kinase activation. In spinal cords of ActB-deficient Inhbb(-/-) embryos, apoptosis in the oligodendrocyte lineage is increased and OLP numbers transiently reduced, but numbers, maturation and myelination recover during the first postnatal week. Smad3(-/-) mice display a more severe phenotype, including diminished viability and proliferation, persistently reduced mature and immature cell numbers, and delayed myelination. Collectively, these findings suggest that, in mammalian spinal cord, Tgfβ ligands and ActB together support oligodendrocyte development and myelin formation.

Astrocyte-derived VEGF-A drives blood-brain barrier disruption in CNS inflammatory disease

In inflammatory CNS conditions such as multiple sclerosis (MS), current options to treat clinical relapse are limited, and more selective agents are needed. Disruption of the blood-brain barrier (BBB) is an early feature of lesion formation that correlates with clinical exacerbation, leading to edema, excitotoxicity, and entry of serum proteins and inflammatory cells. Here, we identify astrocytic expression of VEGF-A as a key driver of BBB permeability in mice. Inactivation of astrocytic Vegfa expression reduced BBB breakdown, decreased lymphocyte infiltration and neuropathology in inflammatory and demyelinating lesions, and reduced paralysis in a mouse model of MS. Knockdown studies in CNS endothelium indicated activation of the downstream effector eNOS as the principal mechanism underlying the effects of VEGF-A on the BBB. Systemic administration of the selective eNOS inhibitor cavtratin in mice abrogated VEGF-A-induced BBB disruption and pathology and protected against neurologic deficit in the MS model system. Collectively, these data identify blockade of VEGF-A signaling as a protective strategy to treat inflammatory CNS disease.

Targeting oligodendrocyte protection and remyelination in multiple sclerosis

Multiple sclerosis is an inflammatory demyelinating disease of the brain and spinal cord with a presumed autoimmune etiology. Conduction block in demyelinated axons underlies early neurological symptoms, whereas axonal transection is believed responsible for more permanent later deficits. Approved treatments for the disease are immunoregulatory and reduce the rate of lesion formation and clinical exacerbation, but are only partially effective in preventing the onset of disability in multiple sclerosis patients. Approaches that directly protect myelin-producing oligodendrocytes and enhance remyelination may improve long-term outcomes and reduce the rate of axonal transection. Studies in genetically modified animals have improved our understanding of mechanisms underlying central nervous system pathology in multiple sclerosis models, and have identified pathways that regulate oligodendrocyte viability and myelin repair. However, although clinical trials are ongoing, many have been unsuccessful, and no treatments are yet approved that target these areas in multiple sclerosis. In this review, we examine avenues for oligodendrocyte protection and endogenous myelin repair in animal models of demyelination and remyelination, and their relevance as therapeutics in human patients.