Intracranial Control with Combined Dual Immune-Checkpoint Blockade and SRS for Melanoma and NSCLC Brain Metastases

PURPOSE/OBJECTIVE(S)

It is unknown whether the use of dual immune-checkpoint inhibition (D-ICI) combined with stereotactic radiosurgery (SRS) affects local control of brain metastases (BMs). We sought to characterize the efficacy of SRS and D-ICI in patients with BMs in a large, single-institution cohort.

MATERIALS/METHODS

Patients with melanoma and non-small cell lung cancer (NSCLC) BMs treated with SRS from January 1, 2016 to August 1, 2022 were evaluated. Patients were stratified by treatment with D-ICI versus single ICI (S-ICI). Concurrent ICI was defined as ICI given within four weeks of SRS. Local recurrence (LR), intracranial progression (IP), and overall survival (OS) were estimated using competing risk and Kaplan-Meier analyses. IP included both local and distant intracranial recurrence.

RESULTS

One thousand seven hundred four SRS-treated BMs from 288 patients met inclusion criteria. 55% of patients were symptomatic from their BMs at presentation. Median age, KPS, number of lesions, and SRS courses were 64 (Q1Q3:56-70.5), 90 (80-90), 2 (1-4), and 1 (1-2), respectively. One hundred twenty-eight (44%) melanoma and 160 (56%) NSCLC patients were included. 82 (28.5%), 129 (44.8%), and 77 (26.7%) patients were treated with D-ICI, S-ICI, or SRS alone. Median SRS dose, fractions, and PTV were 20 (Q1Q3:20-25), 1 (1-5), and 0.3cc3 (0.1-1.2). The median follow-up was 14.3 months. One hundred twenty-seven (7.45%) BMs recurred post-SRS and the median time to LR was 4.8 months (Q1Q3:3.0-9.2). On competing risk analysis, LR was significantly reduced with D-ICI (HR: 0.452, p = 0.0024), but not with S-ICI (HR: 0.693, p = 0.0596) compared to SRS alone. The 1-year LR was 3.77% (95% CI = 2.19-6.00), 6.8% (5.19-8.70), and 8.96% (6.48-11.93) with D-ICI, S-ICI, and SRS alone. The median time to IP was 4.1 months (Q1Q3 = 2.9-9.5). On competing risk analysis, IP was significantly reduced with D-ICI (HR = 0.638, p = 0.031), but not with S-ICI (HR = 0.756, p = 0.106) compared to SRS alone. 1-year IP was 40.05% (95% CI = 29.14-50.70), 51.86% (42.78-60.19), and 58.49% (46.30-68.84) with D-ICI, S-ICI, and SRS alone. Concurrent delivery of D-ICI and SRS significantly reduced IP (HR = 0.463, p = 0.0071), whereas other combinations of timing and ICI did not reach significance. Median OS was 11.9 months after SRS. On Kaplan Meier analysis, OS was significantly improved with D-ICI (HR = 0.616, 95% CI = 0.412-0.923, p = 0.019), but not with S-ICI (HR = 0.877, 95% CI = 0.633-1.217, p = 0.433) compared to SRS alone. Hospitalizations (p = 0.021) and immune-related adverse events (irAEs) (p<0.001) were increased with D-ICI. Any grade radiation necrosis (RN) was also increased with D-ICI (p = 0.013), but neurologic adverse events were comparable across cohorts (p = 0.572).

CONCLUSION

D-ICI combined with SRS was associated with improved local control, intracranial control, and overall survival compared to SRS alone, whereas S-ICI was not associated with an improvement in these outcomes. However, D-ICI was also associated with increased risks of irAEs and RN.

A Systematic Review and Meta-Analysis of Toxicity in Oropharyngeal Cancer Patients Treated with Proton Therapy

PURPOSE/OBJECTIVE(S)

Proton radiotherapy (PRT) is an emerging treatment modality for patients with oropharyngeal cancer (OPC). Due to its dosimetric properties, PRT is hypothesized to be associated with lower rates of acute and late toxicity than photon intensity modulated radiotherapy (IMRT). Current evidence supporting PRT in this setting is limited to small, single institution reports. We sought to examine pooled rates of PRT toxicity from the current literature.

MATERIALS/METHODS

A systematic review of PubMed, Embase, and Web of Science was performed. Articles published from 1980-2022 that contained >10 patients treated with definitive or adjuvant PRT for OPC were included. From these studies acute and late clinician rated adverse events (CRAEs) were extracted. The primary outcomes were the pooled rates of grade 3 or higher (G3+) acute CRAEs. The secondary outcomes were the pooled rates of late CRAEs. Pooled rates were estimated using random effects models for CRAEs that were reported in ≥3 studies and graded using Common Terminology Criteria for Adverse Events (CTCAE). In studies that reported both PRT and IMRT, a mixed effects log odds ratios (ORs) was used to compare risk of CRAE between modalities.

RESULTS

A total of 8 studies (5 retrospective, 3 prospective) with 291 patients treated with PRT for OPC were identified. The majority of patients were men (90%) with HPV-associated disease (93%) treated with definitive intent (56%). Primary tumor was most frequently tonsil (55%); 58% had T1-2, and 60% had N2-3 disease (AJCC7). Estimated pooled rates of G3+ acute CRAEs were as follows: dermatitis: 22%, mucositis: 38%, xerostomia: 1.6%, dysphagia: 15%, and weight loss: 1.9%. Estimated pooled rates of G2+ acute CRAEs were as follows: dermatitis: 73%, xerostomia: 12%, weight loss: 14%, and dysgeusia: 29%. Rate of acute hospitalization was 10%. In terms of late toxicities of PRT, the pooled rate of G2+and G3+ xerostomia were 22.5% and 1.2%, respectfully, while the rates G2+ and G3+ dysphagia were 15.6% and 2.6%, respectfully. Among the included studies, 4 studies reported CRAEs from patients treated with IMRT. Due to inconsistent reporting of CRAEs, only use of feeding tube (FT) could be compared between treatment modalities. PRT was associated with significantly lower FT use in the acute setting compared to IMRT - 18% versus 28%, respectively (log OR -0.88, P<0.001). Long term FT use was not significantly different between PRT and IMRT - 1.4% versus 2.7%, respectively (log OR -0.95, P = 0.24).

CONCLUSION

In the largest pooled analysis of PRT for OPC to date, PRT was associated with a 3-fold reduction of acute, but not late, FT use compared to IMRT. The pooled rates of other PBT CRAEs appear to be at least similar to, if not less than, those reported on IMRT trials treating similarly selected patients. Ultimately, heterogeneity in reporting PRT toxicity outcomes greatly reduces the interpretability of these data and limits proton-photon comparisons. Maximizing consistency of CRAE reporting in future studies is critical.

Extrapulmonary Small Cell Carcinoma: A Single Institution Review of Brain Metastases, Treatment Paradigms and Patient Outcomes

PURPOSE/OBJECTIVE(S)

Extrapulmonary small cell carcinoma (EPSCC) is a rare entity with 1,000 cases reported annually in the U.S. It can originate in a variety of sites outside of the lung, and even with locoregional disease, relapse is common, and survival is poor. Prophylactic cranial irradiation (PCI) can improve survival in small cell lung carcinoma, however in the setting of EPSCC its role has not been clearly defined. We offer a single institution retrospective review of EPSCC, outlining the incidence of brain metastases, treatment paradigms, and patient outcomes.

MATERIALS/METHODS

Patients with available records were identified from an institutional database. Demographic, disease-related, and treatment details were abstracted from the electronic medical record. Clinical outcomes were obtained by medical record review and brain metastases were identified through diagnostic imaging. Patients were classified as having brain metastases at diagnosis or in follow-up. Brain metastasis-free survival (BMFS) was defined as the duration of time from diagnosis to the development of brain metastases, and extracranial progression-free survival (ePFS), as the duration of time from diagnosis to progression of disease outside the brain. Time to event outcomes were summarized using the Kaplan-Meier method. Analyses were performed using R version 3.6.

RESULTS

In total, 68 patients met eligibility criteria for analysis. The majority were male (66%) and median age was 68. The most common primary sites were genitourinary (32%) and gastrointestinal/hepatobiliary (22%). Thirty-eight patients (56%) had diagnostic brain imaging at time of diagnosis, with brain metastases present in 5 (13%). Treatment was delivered to 53 patients (80%) and treatment modalities included chemotherapy (n = 46), radiotherapy (n = 21), and surgery (n = 18). Median follow-up was 9.3 months for all patients and 10.3 months for surviving patients. Overall, 12 patients were observed to have brain metastases: 5 at diagnosis and 7 in follow-up. The competing risk of death without brain metastases at 1 year was 51.5%. Four of 5 patients with de novo brain metastases received WBRT. Of the 7 patients with subsequent brain metastases, 1 received salvage WBRT and 3 received salvage SRS. In total, 49 patients died and median OS was 10.0 months. Those with brain metastases had no significant difference in OS when compared to those without brain metastases (10.8 months v. 9.4 months). There was no association between primary type and survival.

CONCLUSION

EPSCC is a rare entity that is most commonly diagnosed in the genitourinary system. In contrast to SCLC, the incidence of brain metastases is uncommon. No difference in survival was observed between patients with or without brain metastases. While retrospective studies must be interpreted with caution, our data suggest that the risks of PCI may outweigh the benefits. Further studies investigating the role of brain imaging surveillance, as well as the optimal management of brain metastases, is warranted.

Environmental Toxicity of Driving Distance to External Beam Radiotherapy (EBRT) for Head and Neck Cancer Patients

PURPOSE/OBJECTIVE(S)

For many patients undergoing external beam radiotherapy (EBRT), distance from home to treatment center is significant and require housing in closer proximity to minimize this travel burden. Patient transport also contributes significantly to the carbon footprint of EBRT. We sought to define the difference of carbon dioxide (CO2) emissions from commuting for patients who stay at a charity housing (CH) facility during treatment for head and neck cancer (HNC) versus a commute from home.

MATERIALS/METHODS

Patients with HNC were enrolled in an IRB-approved prospective protocol from 2019-2021. A distance of 3 miles (mi) was calculated from CH to our facility using Google Maps. Driving distance from home was indicated by patient self-report. Distance traveled per day Mon-Fri was doubled to account for driving to and from treatment. It was assumed that patients staying at CH returned home on weekends and that all used a standard, gasoline powered automobile for transportation to and from home. Transportation from CH to treatment was via a gasoline powered, 6-person shuttle. Both forms of transport were considered light-duty vehicles (LDV) with mileage and tailpipe emissions corresponding to the US on-road average (23.7 mi per gallon and 0.84 lb CO2/mi). For estimation of CH emissions, conversions were made from the reported electricity bill multiplied by the North Carolina grid emissions rate of 0.698 lb CO2/kWh. Natural gas used by CH for heating (prorated per patient) was estimated using the Piedmont Natural Gas rate (located in NC) and the monthly gas bill. Emissions from patient homes were assumed to be similar for patients commuting and making use of CH and therefore ignored.

RESULTS

Forty-nine patients enrolled in the study: 38 drove themselves to treatment daily, and 2 stayed at CH. The remaining 9 patients indicated that they stayed with friends/family or in a hotel where travel distance to DCI was unknown. CH electricity emissions were estimated to be 8,823 lb CO2/month. CH gas emissions were estimated to be 2,210.6 lb CO2/month. Emissions at CH were calculated as 137.9 lb CO2 per patient per month. The median emissions of those who drove daily per course of EBRT was 1205.4 lb CO2 (IQR 366.0 - 2221.2). For the 2 patients who stayed at the CH, total mi per course were 650 and 774. Including emissions of CH, emissions per patient were 1305.6 and 1523.2 lb CO2. If these patients were to have driven daily from their home, emissions would have been doubled (2368.8 and 2646 lb CO2, respectively). CH was estimated to result in fewer emissions for those that live ≥ 12 miles from the treatment facility.

CONCLUSION

Affordable and safe housing, such as charity housing is not only convenient for patients, but also reduces the environmental impact of travel for care for HNC. Patients who stayed at the charity housing in this study reduced their emissions from travel by nearly a half compared to driving daily in a personal vehicle. Further studies are imperative to continue to measure and mitigate the environmental toxicity of cancer care.

The Environmental Impact of Radiation Oncology: The "Footprint" of External Beam Radiation Therapy

PURPOSE/OBJECTIVE(S)

There is a growing concern for the healthcare sector's impact on the environment. Prior carbon impact studies in radiation oncology have been limited in scope and methodology. This study aims to fill this gap by using an internationally recognized cradle-to-grave life cycle assessment (LCA) approach to quantify all environmental impacts from raw material extraction to product disposal for external beam radiation therapy (EBRT) in treating the most commonly diagnosed cancers.

MATERIALS/METHODS

This LCA was performed in accordance with ISO 14040 and 14044 at a single academic medical center. It quantified the environmental impact of EBRT across four categories: global warming potential (GWP), carcinogenic and non-carcinogenic human toxicity, and respiratory effects (PM2.5), from initial consultation to the completion of the last EBRT fraction for each disease site. Data collection involved weighing all materials used, measuring/calculating building and equipment electricity usage (e.g., HVAC and Linacs), and recording patient and staff transit. The study analyzed the impact of both minimum and maximum fractionations for each disease site and simulated alternative clinical scenarios such as telemedicine, renewable energy use and hypofractionation.

RESULTS

Regardless of disease site, there were significant differences in the environmental impacts associated with transit, electricity and supplies for EBRT treatment cycles. Staff and patient transport contributed the most, accounting for >92% of the total environmental impact including GWP (5.02x102 ± 9.38x101 kgCO2eq), carcinogenic (6.25x10-5 ± 1.23x10-5 CTUh) and non-carcinogenic human toxicity (1.16x10-4 ± 2.35x10-5 CTUh). Electricity accounted for 1-13% of the total impact, with most impact arising from respiratory effects (3.05x10-2 kg ± 2.72x10-3 PM2.5). The impact of supplies and materials was less than 3% across all categories. Alternative scenario modeling showed that telemedicine had a maximum impact reduction of 3.5% (2.54x 101kgCO2eq) for GWP, while renewable energy use had a maximum impact reduction of 8% (2.37 x 10-2 PM2.5) for respiratory effects. Reducing the number of total treatment days via hypofractionation can reduce GWP by 67-78% and carcinogenic emissions by 63-77% (3.48 x 102 - 5.53 x 102 kgCO2eq) and (3.73 x 10-5 - 6.85 x 10-5CTUh), respectively, with variation depending on the total number of fractions.

CONCLUSION

This study provides a comprehensive environmental impact assessment for EBRT among the most commonly treated disease sites, establishing a baseline metric and identifying targets for impact reduction. We are currently performing a multi-center validation study to be completed by June 2023. Our findings fill an important gap in cancer care and are critical for developing sustainable practices in the face of increasing demand for radiotherapy in a changing climate. LCAs evaluating all aspects of cancer care will be essential for promoting equitable and sustainable care.

Prophylactic vs. Reactive Gastrostomy Tube Placement in Patients Treated with Radiotherapy for Head and Neck Cancer

PURPOSE/OBJECTIVE(S)

Radiotherapy (RT) for head and neck cancer (HNC) can cause acute toxicities resulting in weight loss warranting alterative enteral access. Some institutions favor prophylactic gastrostomy tube (GT) placement to prevent malnutrition at the forefront, while others choose to reactively place tubes if nutritional deficits arise. Though prophylactic GT placement may limit on-treatment weight loss, this approach may result in unneeded GT placement and may potentially impact long-term swallowing function.

MATERIALS/METHODS

Patients with HNC treated with CRT from 2018-2021 were reviewed. GT placement prior to CRT (prophylactic [ppx] tube) was performed at the discretion of the treating radiation oncologist. The remainder of patients were treated with reactive (rx) GT placement in the event of on-treatment weight loss approaching 10-15%. Patient, disease and treatment factors were abstracted from the medical record. Primary endpoints were placement of GT in the rx group, weight change at the end of RT, and time to tube removal.

RESULTS

In total, 278 patients were identified; 35 GT-dependent patients and 22 patients with nasal cavity/paranasal sinus cancers were excluded, yielding 221 for analysis. Baseline factors associated with GT group included age, ECOG, baseline swallowing function, primary site, T and N stage, stage group, and treatment year. Treatment factors associated with GT group were: neck target (bilateral v. unilateral/none), concurrent chemotherapy, and total dose. Of the 118 patients in the rx group, 14 (12%) required rx GT placement during or within 30 days of CRT. RT completion rates were similar between groups (95-96%, p = 1). GT was removed at last follow-up in 57% of patients in both groups (p = 1). Percent on-treatment weight loss was -8.9% (SD 6.7) and -7.2% (SD 6.1) for the ppx and rx groups, respectively (p = 0.04). Median Kaplan-Meier estimate of time to GT removal was 7.7 months (95% CI 6.0-11.3) and did not differ between groups (log-rank p = 0.87). Factors associated with the placement of rx GT include: concurrent chemotherapy (yes 20% vs. No 0%, p.0007) and baseline FOIS (5 or less 40% vs. 6 or more 9%, p = 0.02). T stage, N stage, overall stage, postoperative RT, degree of neck irradiation were not associated.

CONCLUSION

Reactive gastrostomy tube placement in patients treated with chemoradiotherapy for head and neck cancer patients is feasible and results in low rates of gastrostomy tube placement. There are no observed differences in on-treatment weight loss between patients treated using a prophylactic versus reactive approach. No differences in time to gastrostomy tube removal were observed.