Citations

Abstract PURPOSE Vertebral compression fracture (VCF) is a potential adverse effect following stereotactic body radiation therapy (SBRT) for spinal metastases. In this analysis, we developed and internally validated a risk stratification model for VCF. METHODS From an initial set of 680 treatments, we excluded those with proton therapy, prior surgical intervention, or missing data. The final dataset had 464 treatments in 313 patients. Delineations of VCF and all radiographic components of the spinal instability neoplastic score (SINS) were determined by a radiologist. Recursive partitioning analysis (RPA) was conducted using separate training (70%), internal validation (15%), and test (15%) sets. The log-rank test was used as the criterion for node splitting. RESULTS With a median follow-up of 21 months, we identified 84 VCF (18%), including 65 (77%) de novo and 19 (23%) progressive fractures. There was a median 9 months (IQR: 3 – 21) to VCF. From an initial set of 15 candidate variables, six were identified using the backwards selection method, feature importance testing, and a correlation heatmap. Four were then selected in the highest-fidelity RPA models: epidural tumor extension, lumbar location, gross tumor volume > 10 cc, and SINS > 6. One point was assigned to each variable, and the resulting multivariate Cox model had a concordance of 0.760. Each one point increase in score was associated with increasing rates of VCF. Low-risk lesions (score: 0-1, n=273) had 2-year freedom from VCF of 92%, compared to 80% for intermediate-risk (score: 2, n=99) and 56% (score: 3-4, n=92) for high-risk lesions (p < 0.0001). Cumulative incidence curves with death as a competing risk showed increased VCF with higher scores via Gray’s test (p < 0.001). CONCLUSIONS Our internally-validated model identifies a subgroup of patients with high risk for VCF who may benefit from prophylactic surgical stabilization or vertebroplasty.

Abstract IntroductionRadiotherapy is considered standard of care for adjuvant peri-operative treatment of many spinal tumors, including those with instrumented fusion. Unfortunately, radiation treatment has been linked to increased risk of pseudoarthrosis. Newerfocused radiotherapy strategies with enhanced conformalitycould offer improved fusion rates for these patients, but this has not been confirmed.MethodsWe performed a retrospective analysis of patients at three tertiary care academic institutions withprimary and secondary spinal malignancies that underwent resection, instrumented fusion, and peri-operative radiotherapy. Two board certified neuro-radiologists used theLenke fusion score to grade fusion status at6 and 12-months after surgery. Secondary outcomes includedclinical pseudoarthrosis, wound complications, and the effect of radiation timing, radiobiological dose delivered, the use of photons versus protons, tumor type, tumor location,and use of autograft on fusion outcomes.ResultsAfter reviewof 1252 spinal tumor patients, there were 60 patients with at least 6 months follow-up that were included in our analyses. Twenty-five of these patients received focused radiotherapy,20 patients received conventional radiotherapy, and 15 patients were treated with protons. There was no significant difference between the groups for covariates such assmoking status,obesity, diabetes, intraoperative use of autograft, and use of peri-operative chemotherapy. There was a significantly higher rate of fusion for patients treated with focused radiotherapy compared to those treated with conventional radiotherapy at 6-months (64.0% versus 30.0%, Odds ratio: 4.15, p=0.036) and 12-months (80.0% versus 42.1%, OR: 5.50, p=0.022). There was a significantly higher rate of clinical pseudoarthrosis in the conventional radiotherapy cohortcompared to patients in the focused radiotherapy cohort (19.1% versus 0%,p=0.037). There was no difference in fusion outcomes for any of the secondary outcomes except for use of autograft. The use ofintra-operative autograft was associated with an improved fusion at 12-months (66.7% versus 37.5%, OR: 3.33, p=0.043). ConclusionFocused radiotherapy may be associated withan improved rate of fusion and clinical pseudoarthrosis when compared to conventional radiation delivery strategiesin patients with spinal tumors.Use of autograft at the time of surgery may be associated with improved 12-month fusion rates.Further large-scale prospective and randomized controlled studies are needed to better stratify the effects of radiation delivery modality in these patients.

Background: Optimal patient selection for radiotherapy in pancreatic ductal adenocarcinoma (PDAC) is unestablished. Molecular profiling may select patients at high risk for locoregional recurrence (LRR) who would benefit from radiation. Methods: We included resectable pancreatic cancer (R-PDAC) patients, divided into training and validation cohorts, treated among three institutions with surgery and adjuvant chemotherapy, and borderline resectable or locally advanced pancreatic cancer (BR/LA-PDAC) patients treated with chemotherapy with or without radiation at the primary study institution. We isolated RNA from R-PDAC surgical specimens. Using NanoString, we identified miRNAs differentially expressed between normal and malignant pancreatic tissue. ElasticNet regression identified two miRNAs most predictive of LRR in the training cohort, miR-181b/d and miR-575, which were used to generate a risk score (RS). We evaluated the association of the median-dichotomized RS with recurrence and overall survival (OS). Results: We identified 183 R-PDAC and 77 BR/LA-PDAC patients with median follow up of 37 months treated between 2001 and 2014. On multivariable analysis of the R-PDAC training cohort (n = 90), RS was associated with worse LRR (HR = 1.34; 95%CI 1.27–11.38; p = 0.017) and OS (HR = 2.89; 95%CI 1.10–4.76; p = 0.027). In the R-PDAC validation cohort, RS was associated with worse LRR (HR = 2.39; 95%CI 1.03–5.54; p = 0.042), but not OS (p = 0.087). For BR/LA-PDAC, RS was associated with worse LRR (HR = 2.71; 95%CI 1.14–6.48; p = 0.025), DR (HR = 1.93; 95%CI 1.10–3.38; p = 0.022), and OS (HR = 1.97; 95%CI 1.17–3.34; p = 0.011). Additionally, after stratifying by RS and receipt of radiation in BR/LA-PDAC patients, high RS patients who did not receive radiation had worse LRR (p = 0.018), DR (p = 0.006), and OS (p < 0.001) compared to patients with either low RS or patients who received radiation, irrespective of RS. Conclusions: RS predicted worse LRR and OS in R-PDAC and worse LRR, DR, and OS in BR/LA-PDAC. This may select patients who would benefit from radiation and should be validated prospectively.

e20554 Background: The paradigm for locally advanced non-small cell lung cancer has been markedly altered to include maintenance durvalumab (D) post completion of definitive chemoradiation (CRT) following the publication of the Pacific trial in 2018. The toxicity of this treatment has not been well evaluated in the real-world setting. Methods: We identified 42 patients (pts) with Stage IIB-IIIC NSCLC treated at Mayo Clinic Rochester between 6/1/2018 and 10/1/2020 who received definitive CRT followed by maintenance D. Data were abstracted by retrospective chart review under an IRB approved protocol. Results: Median age was 66 yrs (range 47-90) and 62% were women. Primary lung cancer histology included 19 adenocarcinoma, 20 squamous cell, and 3 adenosquamous. The distribution of stages was: IIB (4/42), IIIA (15/42), IIIB (19/42), IIIC (4/42). Approximately half of patients had PDL1 expression > 25% (20/42). With a median follow up of 12.2 months (calculated from first cycle of D; range 4.2-30.5 months), 14 had completed one year of maintenance D, 16 were receiving ongoing D, and 10 stopped D early with 6/12 discontinuing due to disease progression (4/6 local progression, 2/6 distant progression). Other reasons for discontinuation (5/10) included grade 3 colitis, grade 2 hepatitis, aspergillus lung infection, and flare of autoimmune disorders. One quarter of patients experienced grade 2 radiation pneumonitis (RP; 10/42) with median time to development of RP 78 days from end of CRT and 45 days from start of D. RP was determined by multidisciplinary review of imaging and treatment fields. 17/42 patients developed immune related adverse events (see Table for details). There was minimal overlap between the patients who experienced pneumonitis and immune related toxicity; 2/17 had both pneumonitis and immune related toxicity (hepatitis, thyroiditis). Conclusions: In our early experience with the Pacific regimen, 29% of patients did not complete D due to either toxicity or progression during D administration. Pneumonitis was common (10/42 patients) although there were no grade 3 events. Nearly half of the patients developed an immune-related adverse event. Further analysis is needed to evaluate the real-world toxicity of this treatment as well as oncologic outcomes.[Table: see text]

239 Background: After trastuzumab (T) approval for advanced HER2-positive E/GEJ-AC, HER2 testing has increased in patients (pts) with resectable disease. Neoadjuvant carboplatin/paclitaxel chemoradiation (nCP-CRT) is a common therapy approach. We performed the largest evaluation, to our knowledge, of the prognostic impact of HER2 in E/GEJ-AC pts treated with nCP-CRT. Methods: We retrospectively reviewed medical records of all trimodality-eligible (T2+ or N+) pts with E/GEJ-AC who started nCP-CRT (usually 50.4 Gy) with planned surgery at Mayo Clinic (2014-2019). HER2 was tested using standard criteria for HER2 positivity (ie, immunohistochemistry 3+ or amplification by in situ hybridization). Clinicopathologic data and time to recurrence (TTR), disease free survival (DFS), overall survival (OS), survival after recurrence (SAR), and pathologic complete response (pCR – ie, no residual tumor in primary or nodes) were collected. Kaplan Meier and multivariate Cox analysis were used. Results: Of 161 consecutive eligible pts, HER2 status was available in 107 pts (HER2-positive n=26, HER2-negative n=81) of whom n=82 had surgery and n=19 had pCR. Most tumors were clinical T3 (80%) or N+ (81%), histologic grade 3 of 3 (62%). HER2 positivity was significantly associated with lower grade, but not with age, clinical T or N, or ECOG performance status (PS). A similar proportion of HER2-positive ( vs negative) pts had surgery. Among pts who had surgery, pCR rates were lower in HER2-positive ( vs negative) pts (11% [2/19] vs 27% [17/63]). After a median follow up of 23 mo, DFS and TTR were significantly shorter in HER2 positive ( vs negative) pts, independent of other pretreatment covariables (Table). Yet OS was comparable. Lung recurrence was enriched in HER2 positive ( vs negative) pts. Among pts with recurrence, SAR was longer in HER2-positive vs -negative pts. A total of 53% (10/19) of previously HER2-positive pts received T-based therapy after recurrence, and these pts were the drivers of favorable SAR (median 22 mo in n=10 HER2-positive pts who received T vs 11 mo in n=9 HER2-positive pts who did not receive T vs 11 mo in n=40 HER2-negative pts; P log-rank=.01). Conclusions: HER2 positivity ( vs negativity) is independently associated with shorter TTR and DFS, but more comparable OS. The adverse association of HER2 on tumor response and TTR may have been largely overcome through enhanced survival after recurrence, although OS data are maturing. These data may have implications for the design of endpoints in future curative-intent anti-HER2 trials. [Table: see text]

Abstract Background Patterns of recurrence and survival with different surgical and radiotherapy (RT) techniques were evaluated to guide RT target volumes for patients with temporal lobe glioma. Methods and Materials This retrospective cohort study included patients with World Health Organization grades II to IV temporal lobe glioma treated with either partial (PTL) or complete temporal lobectomy (CTL) followed by RT covering both the parenchymal and dural resection bed (whole-cavity radiotherapy [WCRT]) or the parenchymal resection bed only (partial-cavity radiotherapy [PCRT]). Patterns of recurrence, progression-free survival (PFS) and overall survival (OS) were evaluated. Results Fifty-one patients were included and 84.3% of patients had high-grade glioma (HGG). CTL and PTL were performed for 11 (21.6%) and 40 (78.4%) patients, respectively. Median RT dose was 60 Gy (range, 40-76 Gy). There were 82.4% and 17.6% of patients who received WCRT and PCRT, respectively. Median follow-up time was 18.4 months (range, 4-161 months). Forty-six patients (90.2%) experienced disease recurrence, most commonly at the parenchymal resection bed (76.5%). No patients experienced an isolated dural recurrence. The median PFS and OS for the PCRT and WCRT cohorts were 8.6 vs 10.8 months (P = .979) and 19.9 vs 18.6 months (P = .859), respectively. PCRT was associated with a lower RT dose to the brainstem, optic, and ocular structures, hippocampus, and pituitary. Conclusion We identified no isolated dural recurrence and similar PFS and OS regardless of postoperative RT volume, whereas PCRT was associated with dose reduction to critical structures. Omission of dural RT may be considered a reasonable alternative approach. Further validation with larger comparative studies is warranted.

Abstract BACKGROUND Treatment of temporal lobe glioma (TLG) frequently includes partial or complete temporal lobectomy (TL) followed by radiotherapy (RT). However, there are two approaches for temporal resection cavity RT, 1) standard target volumes (STV) targeting the entire TL resection cavity, dura, and peri-tumoral brain parenchyma or 2) modified target volumes (MTV) targeting only the adjacent peri-tumoral brain parenchyma. We report patterns of failure and a dosimetric comparison of these approaches. MATERIALS AND METHODS This was a retrospective review of 49 patients with WHO grade II-IV TLG who underwent partial or complete TL and post-operative RT between 1998 and 2018. Progression-free survival (PFS) was estimated using the Kaplan-Meier method. RESULTS The median patient age was 56 years (range,21–76). Patients were diagnosed with glioblastoma (n=32,65%), anaplastic glioma (n=10,20%) and low-grade glioma (n=7,14%). Treatment included partial TL with STV (n=33,67%), partial TL with MTV (n=5,10%), complete TL with STV (n=8,16%) and complete TL with MTV (n=3,6%). Mean RT dose was 60 Gy (range,40–76) in 30 fractions (range,15–39). At median follow-up time of 18 months (range, 3–161), 44 patients (90%) experienced recurrence: 34 (77%) in-field, 5 (11%) out-of-field, and 5 (11%) both in- and out-of-field. Among the 39 in-field failures, the location of recurrence included brain parenchyma (n=38,97%), ventricle (n=6,15%), and dura (n=5,13%). No patient experienced isolated dural recurrence regardless of tumor grade, extent of TL, or radiation volume. Median PFS was 20 months (95% confidence interval [CI]: 15–24). RT volume (STV vs. MTV) was not associated with worsened PFS (hazard ratio: 1.1, 95% CI: 0.5–2.6). MTV was associated with significant reductions in mean or max doses to brain stem, optic chiasm, optic nerves, hippocampus, and pituitary compared to STV. CONCLUSION Omitting RT to the entire TL cavity may reduce dose to multiple normal tissues with no detriments in dural recurrence or PFS.

Abstract Introduction Polycythemia vera (PV) and Essential thrombocytosis (ET) progress to myelofibrosis (MF). Extramedullary hematopoeisis (EMH) is common in patients with primary or secondary MF, and can occur in the lungs. Pulmonary EMH can cause recurrent pleural effusions, pulmonary hypertension, and right heart failure with symptoms of dyspnea, cough, and fatigue. Low dose single fraction whole lung irradiation (WLI) has been utilized at our institution, and our preliminary report of 4 patients noted symptomatic improvement with no reported acute side effects. Here we report on a larger cohort of 57 patients as well as long term outcomes for 20 of those patients, including the original 4 patients. Methods We performed a retrospective review of 57 patients with myelofibrosis and pulmonary EMH who received single fraction WLI to a dose of 100 cGy at the Mayo Clinic from March 2001 to March 2014. Data related to the following parameters was collected: initial diagnosis, age at initial diagnosis, date of progression to myelofibrosis, initial treatment prior to radiation therapy, whole body bone marrow scan findings if available, and response to WLI. Overall survival was measured using the Kaplan Meier method. Chi-square analysis was used to evaluate predictors of response to WLI. Results The median age at first WLI was 67 years (45-84 years), and 33 patients (58%) were male. Twenty-two patients (39%) had a diagnosis of primary MF, 27 patients (47%) had PV or ET, and 8 patients (14%) had another cause of secondary MF. At the time of WLI, 27 patients (47%) were on supplemental oxygen, and 3 patients (5%) were in the intensive care unit. Hydroxyurea (n=14, 25%), JAK2 inhibitors (n=9, 16%), Anagrelide (n=3, 5%), and Thalidomide and Prednisone (n=3, 5 %) were the most frequent treatments prior to WLI. EMH was confirmed on bone scan in 38 patients (67%). In the remaining 19 patients, a diagnosis of EMH was made based on clinical impression. This included symptoms of dyspnea, cough, and fatigue, echocardiographic findings of pulmonary hypertension, and in some patients recurrent pleural effusions (n=13), positive lymph node biopsy (n=2), or thoracentesis (n=1). Twenty-eight (49%) patients had other active cardiac or pulmonary conditions that likely contributed to their clinical symptoms. These patients were receiving concurrent treatment for their other conditions. In some patients there were multiple coexisting conditions. Clinical improvement occurred in 30 patients (53%). The median time from WLI to symptomatic improvement was 10 days (1-174 days). Twenty-four patients (42%) did not have clinical improvement. Nine patients (16%) had stable symptoms, 15 patients (26%) had progressive symptoms, and 3 patients (5%) had insufficient follow up. In the group of patients with concurrent active cardiac or pulmonary conditions, 15 patients (54%) had clinical improvement following WLI. In the 29 patients who had solitary EMH, 15 (52%) patients had clinical improvement. There was no difference in response rates related to oxygen use at the time of WLI. Six patients (11%) received WLI on multiple occasions. There was no difference in the percentage of patients with positive bone marrow scans (67%) in the 2 groups. The median overall survival was 259 days for all patients. Patients who improved after WLI had a median survival of 325.5 days compared to 122.5 days for patients who did not improve. No new hematologic abnormalities temporally related to WLI were reported. Long term follow up beyond 1 year was available for 20 patients (35%). No patients developed pneumonitis or pulmonary fibrosis that was considered related to WLI. One patient received a diagnosis of an upper esophageal squamous cell carcinoma 6 years after WLI and allogeneic stem cell transplant. Conclusion Our prior study showed WLI is safe and effective in a small number of patients with isolated pulmonary EMH from MF. The current study confirms the long term safety of this approach. Our results suggest WLI may contribute to symptomatic improvement in 1/2 of patients, even in the common clinical situation of multiple coexisting cardiac and pulmonary conditions. Repeat WLI is also well tolerated and can result in symptomatic improvement. We did not find any factors that predicted response to WLI. WLI should be considered in patients who have clinically proven pulmonary EMH and associated symptoms, even in the presence of other conditions, and can be repeated safely. Disclosures No relevant conflicts of interest to declare.