Concurrent Radiation and Immunotherapy Augments Local Immunity and Improves Survival in Aneuploid NSCLC

PURPOSE/OBJECTIVE(S)

Over 500 clinical trials combining radiation (RT) and immune checkpoint blockade (ICB) have been initiated based on preclinical evidence that RT can augment local immunity and improve the efficacy of ICB. However, many recent clinical trials have not found a benefit of combining RT and ICB, raising questions about whether a synergy exists. We examined whether RT and ICB interact to beneficially stimulate the immune response in patients and identified biomarkers of response to RT and ICB.

MATERIALS/METHODS

We performed a molecular analysis of 1,740 patients from 3 cohorts. The COSINR dataset is a randomized clinical trial of 22 non-small cell lung cancer (NSCLC) patients treated with concurrent or sequential SBRT and ipilimumab/nivolumab. Paired pre- and on-treatment biopsies of an irradiated metastasis underwent whole exome sequencing and RNA-seq. On-treatment biopsies were obtained after SBRT and prior to ICB (sequential) or after SBRT and one cycle of ICB (concurrent). The UC cohort consisted of targeted DNA sequencing of 58 NSCLC patients treated with ICB alone, sequential RT+ICB, or concurrent RT+ICB. The MSKCC dataset is a pan-cancer cohort of targeted DNA sequencing of 1,660 patients treated with ICB. Aneuploidy score (AS) was defined as the fraction of chromosome arms with arm-level copy number alterations. Survival analyses utilized the Kaplan-Meier method and multivariable Cox proportional hazards models.

RESULTS

In the COSINR trial, SBRT+ICB increased, whereas SBRT alone decreased, expression of effector T cell IFN-gamma and adaptive immune signatures (P<0.05). Established biomarkers of ICB response, including IFN-gamma signature, tumor mutational burden (TMB), PD-L1 expression, and neoantigen burden were not associated with survival (P>0.05). However, patients whose tumors exhibited high (≥median) but not low, AS had improved survival when treated with concurrent vs. sequential SBRT+ICB (1-year overall survival [OS] 100% vs. 17%, P = 0.025). Our findings were corroborated in the UC cohort: high AS tumors treated with RT + ICB had superior 1-year OS compared to those treated with ICB alone (59% vs. 31%, P = 0.021). Among those who received RT + ICB, concurrent treatment improved OS relative to sequential (1-year OS 76% vs. 38%). RT did not improve OS in patients with low (

CONCLUSION

Our findings distinguish the genomic and transcriptomic effects of RT versus RT+ICB and challenge the prevailing paradigm that local ablative RT positively stimulates the immune response. We propose the use of tumor aneuploidy as a biomarker in personalizing treatment approaches for patients with various cancers.

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Affiliation(s)

L F Spurr University of Chicago, Chicago, IL
C Martinez University of Chicago, Chicago, IL
W Kang University of Chicago, Chicago, IL
M Chen University of Chicago, Chicago, IL
Y Zha University of Chicago, Chicago, IL
R Hseu University of Chicago, Chicago, IL
S Gutiontov Department of Radiation and Cellular Oncology, University of Chicago Medical Center, Chicago, IL
W T Turchan University of Chicago, Chicago, IL
C Lynch Northwestern University Feinberg School of Medicine, Chicago, IL
K B Pointer University of Wisconsin-Madison, Madison, WI
E E Vokes Department of Medicine, Section of Hematology/Oncology, University of Chicago, Chicago, IL
C M Bestvina Department of Hematology Oncology, University of Chicago Medical Center, Chicago, IL
J D Patel Lurie Cancer Center, Northwestern University-Feinberg School of Medicine, Chicago, IL
M Diehn Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA
R R Weichselbaum Department of Radiation and Cellular Oncology, The University of Chicago Medicine, Chicago, IL
S J Chmura Department of Medicine, University of North Carolina, Chapel Hill, NC
S P Pitroda Department of Radiation and Cellular Oncology, University of Chicago Medical Center, Chicago, IL

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Hyperfractionated Reirradiation for Locally Recurrent Thoracic Tumors

PURPOSE/OBJECTIVE(S)

For patients with locally recurrent thoracic tumors or second primaries within previously irradiated volumes, hyperfractionated reirradiation (re-RT) may mitigate late toxicity compared to conventional fractionation, but clinical outcomes have not been extensively studied. We herein report our institutional experience with thoracic hyperfractionated reirradiation.

MATERIALS/METHODS

We identified 26 cases among 23 patients treated with re-RT to either primary or metastatic thoracic tumors, 60 Gy in 50 fractions, twice daily over 5 weeks using highly conformal image guided RT with motion management. Nineteen patients had dosimetry data available. The primary outcome was Grade (G2) or higher toxicity rates per CTCAEv5.0. Secondary endpoints were 12-month local control (LC), progression free survival (PFS)-determined by treating physician and/or multidisciplinary tumor board-and overall survival (OS).

RESULTS

Median follow-up was 13 months. Half had non-small cell lung cancer, 95.8% had ultracentral tumors, 57.7% had single prior thoracic RT course; 38.5%, 11.5% and 11.5% received concurrent chemotherapy, immunotherapy, and targeted agents, respectively. Minimum and median intervals between RT courses were 10 and 39.5 months, respectively; 94.7% of re-irradiation plans had overlapping 80% isodose volumes. Median OS and PFS were 13 and 10 months, respectively. Crude 12-month LC was 73.1%. Of those with a recurrence, the first recurrence occurred locally in 6 (54.6%), regionally in 3 (27.3%), and distantly in 8 (72.7%) patients. ≥G2 and ≥G3 toxicity rates were 30.8% and 7.69%, respectively (one G3 atrial fibrillation; one G5 pneumonitis). Using the American Radium Society guidelines for thoracic reirradiation, only 10.5% met all dose volume constraint recommendations.

CONCLUSION

Definitive hyperfractionated thoracic re-RT was well tolerated with promising local control. ≥G3 toxicities were rare. Patients should be counseled on the low but potential risk of life-threatening toxicity. Consensus guidelines for dose constraints may be difficult to meet in reirradiation setting; in this cohort, rates of severe toxicity were low despite exceeding putative constraints in most patients.

Predicting Local Control with Dosimetric Parameters in Patients Receiving Individualized Stereotactic Ablative Radiotherapy for Lung Tumors

PURPOSE/OBJECTIVE(S)

Stereotactic ablative radiotherapy (SABR) is an effective treatment option for lung tumors. The individualized lung tumor SABR (iSABR) trial was a phase II single-arm study that personalized lung tumor SABR dose and fractionation based on tumor size, location, and histology with very low rates of local recurrence (LR). A secondary analysis of this trial was conducted to assess for potential dosimetric predictors of LR, in order to help guide future clinical treatment planning.

MATERIALS/METHODS

From 2011 to 2018, local, regional and distant recurrence data were prospectively collected from 204 patients (261 lung SABR treatments) enrolled in a prospective trial. Baseline characteristics and treatment details were evaluated. Dosimetric and treatment plan parameters were evaluated for their potential to predict LR, using logistic regression and chi-squared analyses.

RESULTS

The majority of treated tumors were peripheral (71%, vs 29% central), primary lesions (76%, versus 24% metastatic), and of adenocarcinoma histology (67%, versus 13% squamous cell carcinoma and 19% other). The median follow-up was 24 months (range 2-95). Twenty-seven (10.3%) LRs occurred, with a median time to LR of 15 months (range 6-81 months). There were no significant associations between the overall cohort and the dosimetric parameters. However, for the multi-fraction cohort, an increased proportion of the PTV receiving 110% and 115% of the prescription dose were associated with lower LR (p = 0.01 and p = 0.01 respectively). Specifically for the 50 Gy in 4 fraction cohort, an increased D1cc, D0.03cc, as well as the proportion of the PTV receiving 110%, 115%, and 120% of the prescription dose were associated with lower LR (p < 0.001, p = 0.001, p = 0.003, p < 0.001, p = 0.004, respectively). There was no association of LR with prescription dose expressed as biologically effective dose using an alpha/beta of 10 Gy (BED10), D99%, or single- versus multi-fraction regimens.

CONCLUSION

SABR for lung tumors using the individualized protocol on this trial showed excellent LR rates. We identified dosimetric parameters that were associated with LR, including V110% and V115% within the multi-fraction cohort, as well as the 50 Gy in 4 fraction cohort the D1cc, D0.03cc, and proportions of the PTV receiving 110%, 115%, and 120% of the prescription dose in the 50 Gy in 4 fraction cohort. Optimal thresholds for these parameters will be identified in further analyses. There did not appear to be an association with LR and BED10, D99%, or comparing single- vs multi-fraction regimens.

Prospective Trial of Using Imaging to Predict Pathologic Response and Clinical Outcomes in Locally Advanced Esophageal Cancer

PURPOSE/OBJECTIVE(S)

Trimodality therapy with chemoradiation (CRT) followed by esophagectomy is the standard of care for locally advanced esophageal cancer. An unresolved question is whether pathologic complete response (pCR) can be assessed non-invasively for patients post-CRT. In this study, we assessed whether diffusion-weighted imaging (DWI) with MRI or PET can be used as predictors of pCR and other clinical outcomes after CRT.

MATERIALS/METHODS

Patients were enrolled on a single-arm institutional trial (PA13-0380) assessing the role of imaging in predicting outcomes in potentially resectable esophageal patients undergoing trimodality therapy. All patients received neoadjuvant CRT, and 29 patients had subsequent surgery. DWI MRI and PET scans were obtained at baseline, 2 weeks after the start of CRT (interim) and 4 to 6 weeks after completion of CRT (follow up). Apparent diffusion coefficients (ADCs) were calculated based on DWI images. Circulating tumor DNA was obtained for 27 patients post-radiation using CAPP-Seq. Mann-Whitney tests compared imaging changes associated with pCR. Discrimination of pCR by imaging changes was quantified by received operating characteristics. Youden's index was applied to select optimal thresholds. Kaplan-Meier analysis was performed to assess differences in overall survival (OS) and progression-free survival (PFS) by changes in DWI, PET, and ctDNA parameters.

RESULTS

Our cohort of 60 patients had a median follow up of 42.7 months, age of 65.4 yrs, and ECOG of 1 at completion of CRT. 90% were male, 58% had a history of smoking, and 85% were white. 83% had adenocarcinoma with the rest squamous cell carcinoma. Stages of the patients ranged from IIA to IIIB. All had moderately (47%) or poorly (53%) differentiated disease. All received 41.4-50.4 Gy in 1.8 Gy fractions with the majority receiving 50.4 Gy (95%). 29 patients underwent surgery after CRT of which 8 (27.6%) had pCR. Mean ΔADC from baseline to mid-treatment was most associated with pCR (AUC = 0.98, p<0.001) for patients undergoing surgery. Max ΔADC from baseline to first follow-up was most associated with OS (p = 0.002) and PFS (p<0.001) for the whole cohort. 27 patients had ctDNA analyzed after RT with the presence of ctDNA significantly associated with worse OS (HR = 0.12, p = 0.05) and PFS (HR = 0.10, p = 0.002). Combining ctDNA and max ΔADC generated a model that was more predictive of OS and PFS than either alone. We found that neither the PET parameters of TLG or SUV max at baseline or changes in these parameters from baseline to mid-treatment or first follow-up were as predictive as DWI.

CONCLUSION

We show that changes in DWI is associated with pCR, OS, and PFS in resectable esophageal cancer patients undergoing CRT. DWI was more predictive than PET and a model combining DWI and ctDNA was the most predictive of clinical outcomes. This study shows the significant promise of using DWI in potentially guiding treatment decisions in esophageal cancer patients and will require validation in a larger cohort.

Investigating Dosimetry and Imaging Biomarkers for Prediction of Major Adverse Cardiac Events Following Locally Advanced Non-Small Cell Lung Cancer Radiotherapy

PURPOSE/OBJECTIVE(S)

Thoracic radiotherapy (RT) may confer major adverse cardiac events (MACE) following treatment. Mean heart dose positively associates with MACE and recent studies show cardiac substructure dosimetry improves MACE prediction. Use of imaging biomarkers with cardiac substructure dose has not been studied for prediction of MACE. We sought to develop an integrated model for cardiac substructure dose and baseline coronary artery calcium (CAC) scoring and establish its relationship to MACE.

MATERIALS/METHODS

A retrospective cohort analysis was performed of consecutive patients with locally advanced non-small cell lung cancer (NSCLC) treated with definitive RT from 2006-2018 at a single institution. Demographics, medical history, cardiac events, and treatments received were recorded. Cardiac substructures were contoured, including the left descending artery (LAD), left main coronary artery (LMCA), left circumflex (LCX), right coronary artery (RCA), TotalLeft (LAD+LMCA+LCX), and TotalCor (TotalLeft+RCA). Doses were measured in 2 Gy equivalent dose. CAC was scored by visual assessment and compared to established automated Agatston scoring. Primary endpoint was MACE incidence. Receiver operating characteristic (ROC) curves assessed dose and CAC metric model performance. Threshold modeling was conducted using the log rank statistic with 95% confidence intervals measured using bootstrap resampling with 1000 iterations. Competing risk models adjusted for death were used to measure cumulative incidence of MACE as well as in univariable and multivariable risk regression modeling. Pearson correlations were used to validate CAC scoring. P-values were two tailed and considered significant at P≤0.05.

RESULTS

Of 233 eligible patients, 61.4% were male with a 68.1 years (range 34.9-90.7) median age. Median follow-up was 73.7 months (range 1.6-153.9). Median overall survival was 34.8 months. Following RT, 22.3% experienced at least one cardiac event at a median time of 21.5 months (range 1.7-118.9). Visual CAC scoring showed significant correlation with automated Agatston scoring (r = 0.72, P=1e-5). While left sided coronary arteries (TotalLeft), mean heart dose (MHD) and CAC scores individually predicted for MACE (AUC = 0.56-0.59), a multivariable model of TotalLeft CAC had the highest ROC analysis performance (AUC = 0.69). On univariable and multivariable competing risk regression analyses, TotalLeft V15 Gy >2.53 cc and CAC score >5 independently associated with MACE (P<0.05). A model incorporating age, TotalLeft CAC>5 and V15>2.53cc, showed incrementally higher MACE incidences for low (9.3%), intermediate (18.4%), and high-risk groups (27.7%) (P<0.01).

CONCLUSION

RT-induced MACE occurs in >20% of those undergoing thoracic RT in a median time of <2 years. We validate significant associations between TotalLeft RT dose and MACE and establish CAC as a predictive risk factor. These findings may serve to inform personalized RT and future cardiac risk in locally advanced NSCLC.

Abstract ES5-2: Circulating tumor DNA analysis for liquid biopsies: Current status and future opportunities

Circulating tumor DNA (ctDNA) represents a promising biomarker for sensitive, specific, and dynamic detection of disease burden in cancer patients. Additionally, ctDNA analysis allows non-invasive access to cancer genomes and therefore can be used for non-invasive tumor genotyping and monitoring of resistance mutations. In this presentation I will describe technical aspects of ctDNA detection and emerging clinical results from recent studies employing ctDNA analysis.

Citation Format: Diehn M. Circulating tumor DNA analysis for liquid biopsies: Current status and future opportunities. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr ES5-2.