The Next Chapter in Immunotherapy and Radiation Combination Therapy: Cancer-Specific Perspectives

Immunotherapeutic agents have revolutionized cancer treatment over the past decade. However, most patients fail to respond to immunotherapy alone. A growing body of preclinical studies highlights the potential for synergy between radiation therapy and immunotherapy, but the outcomes of clinical studies have been mixed. This review summarizes the current state of immunotherapy and radiation combination therapy across cancers, highlighting existing challenges and promising areas for future investigation.

Tumor-Associated Lymphocytes and Breast Cancer Survival in Black and White Women

This case series evaluates whether differences in immune filtration are associated with breast cancer risk in Black vs White women.

CD40 agonism improves anti-tumor T cell priming induced by the combination of radiation therapy plus CTLA4 inhibition and enhances tumor response

Radiation therapy (RT) combined with CTLA4 blockers converts immunosuppressed (cold) mouse triple negative breast cancers (TNBCs) into immune infiltrated (hot) lesions. We have recently shown that targeting the myeloid compartment to improve dendritic cell activation is required for most TNBC-bearing mice to achieve superior therapeutic responses to RT plus CTLA4 inhibitors.

AN0025, a novel antagonist of PGE2-receptor E-type 4 (EP4), in combination with total neoadjuvant treatment of advanced rectal cancer

PURPOSE

To assess the safety and efficacy of AN0025 in combination with preoperative radiotherapy and chemotherapy in either short course (SCRT) or long course radiotherapy (LCRT) settings for those with locally advanced rectal cancer.

PATIENTS AND METHODS

Twenty-eight subjects with locally advanced rectal cancer participated in this multicenter, open-label, Phase Ib trial. Enrolled subjects received either 250 mg or 500 mg of AN0025 once daily for 10 weeks with either LCRT or SCRT with chemotherapy (7 subjects/group). Participants were assessed for safety/efficacy starting from the first dose of study drug administration and were followed for 2 years.

RESULTS

No treatment-emergent adverse or serious adverse events meeting dose-limiting criteria were observed, with only 3 subjects discontinuing AN0025 treatment due to adverse events. Twenty-five of 28 subjects completed 10 weeks of AN0025 and adjuvant therapy and were evaluated for efficacy. Overall, 36.0% of subjects (9/25 subjects) achieved a pathological complete response or a complete clinical response, including 26.7% of subjects (4/15 subjects who underwent surgery) who achieved a pathological complete response. A total of 65.4% of subjects had magnetic resonance imaging-confirmed down-staging ≤ stage 3 following completion of treatment. With a median follow-up of 30 months. The 12-month disease-free survival and overall survival were 77.5% (95% confidence interval [CI]: 56.6, 89.2) and 96.3% (95% CI: 76.5, 99.5), respectively.

CONCLUSIONS

Treatment with AN0025 administered for 10 weeks along with preoperative SCRT or LCRT did not appear to worsen the toxicity in subjects with locally advanced rectal cancer, was well-tolerated and showed promise in inducing both a pathological and complete clinical response. These findings suggest its activity deserves further investigation in larger clinical trials.

Randomized trial of MRI-guided salvage radiotherapy for prostate cancer in 4 weeks vs. 2 weeks (SHORTER)

TPS400

Background: The objective of this randomized clinical trial is to demonstrate that 2 weeks (5 fractions) of real-time MRI-guided radiotherapy (RT) with an MR Linac does not significantly increase patient-reported GI and GU symptoms compared to 4 weeks (20 fractions) of RT 2 years after treatment completion. Methods: Key Eligibility Criteria: Inclusion Criteria 1. Men aged > 18 with histologically confirmed prostate cancer after prostatectomy with detectable PSA. 2. KPS > 70. 3. Patients with no evidence of distant metastatic disease on PET/CT/MRI/bone scan< 180 days prior to enrollment. 4. Ability to receive MRI-guided radiotherapy. 5. Ability to complete the Expanded Prostate Cancer Index Composite (EPIC) questionnaire. Exclusion Criteria 1. Prior history of receiving pelvic RT. 2. Patient with history of IBD. 3. History of bladder neck or urethral stricture. Study Design/Endpoints: This is a randomized phase II non-inferiority trial comparing 5 fractions of ultrahypofractionated RT (32.5 Gy total with optional PSMA/MRI boost to 40 Gy) versus 20 fractions of hypofractionated RT (55 Gy total with optional PSMA/MRI boost to 60 Gy) in the post-operative setting for prostate cancer. Subjects will be stratified based on pre-specified stratification factors and randomized 1:1 to receive 5 or 20 fractions using permuted block randomization. The primary endpoint is the change in patient-reported GI and GU symptoms as measured by EPIC at 2 years from end of treatment. Secondary endpoints will include both the safety endpoints including change in GI and GU symptoms at 3, 6, 12 and 60 months from end of treatment, and multiple efficacy endpoints including time to progression, prostate cancer specific survival and overall survival. Sample Size: The sample size is calculated based on a non-inferiority design. The non-inferiority margins are set to be a change score of 6 points for the GI symptoms and 5 points for the GU symptoms. The standard deviations of the change scores are assumed to be 13.2 for the GI symptoms and 10.5 for the GU symptoms based on estimates generated in RTOG 0415 trial. This level of change in scores are deemed as clinically meaningful. For example, 6 points of change score for GI symptoms corresponds to two symptoms worsening by 1 level (i.e., loose stools and frequency of bowel movements change from “no problem” to “very small problem”) or one of the symptoms worsening by 2 levels (i.e., loose stool change from “no problem” to “small problem”). A sample size of 122 with 61 in each arm will ensure 80% power for GI endpoint and 83% power for GU endpoint to detect non-inferiority using a one-sided two-sample t-test at the significance level of 0.05. Adjusting for a projected 10% EPIC/non-compliance rate, 136 patients (68 per arm) will be randomized. Stratification Factors: Patients will be stratified according to baseline EPIC bowel and urinary domain scores and use of nodal treatment and ADT. Enrollment: 91 patients. Clinical trial information: NCT04422132 .

Impact of the COVID-19 breast cancer screening hiatus on clinical stage and racial disparities in New York City

Background

The impact of the COVID-19 mammography screening hiatus as well as of post-hiatus efforts promoting restoration of elective healthcare on breast cancer detection patterns and stage distribution is unknown.

Methods

Newly diagnosed breast cancer patients (2019–2021) at the New York Presbyterian (NYP) Hospital Network were analyzed. Chi-square and student's t-test compared characteristics of patients presenting before and after the screening hiatus.

Results

A total of 2137 patients were analyzed. Frequency of screen-detected and early-stage breast cancer declined post-hiatus (59.7%), but returned to baseline (69.3%). Frequency of screen-detected breast cancer was lowest for African American (AA) (57.5%) and Medicaid patients pre-hiatus (57.2%), and this disparity was reduced post-hiatus (65.3% for AA and 63.2% for Medicaid).

Conclusions

The return to baseline levels of screen-detected cancer, particularly among AA and Medicaid patients suggest that large-scale breast health education campaigns may be effective in resuming screening practices and in mitigating disparities.

Natural history of lower urinary tract symptoms among men undergoing stereotactic body radiation therapy for prostate cancer with and without a Rectal Hydrogel Spacer

PURPOSE

Stereotactic body radiation therapy (SBRT) is increasingly used for prostate cancer, but has morbidity as both the bladder and rectum are radiated during treatment. Our goal was to document and compare lower urinary tract symptoms (LUTS) among men who underwent SBRT with and without SpaceOAR hydrogel (Augmenix, Inc., Bedford, MA).

METHODS

We performed a retrospective analysis of 87 men (50 SpaceOAR and 37 non-SpaceOAR) who underwent SBRT. Primary outcomes were patient reported symptoms during radiation therapy, pharmacotherapy usage, and urologic and bowel survey scores up to 6-months post-SBRT.

RESULTS

78% of men were on α-inhibitors at the end of SBRT, an increase from 27.6% baseline usage (p < 0.001). Post-SBRT urinary frequency was more common in the non-SpaceOAR group versus the SpaceOAR group (68% versus 38%, p = 0.006), as was nocturia (35% vs. 8%, p = 0.002). Acute gastrointestinal symptoms did not differ. 58.8% of men were on α-inhibitors at 6-months of follow-up post-SBRT, an increase from 27.6% baseline usage (p < 0.001). Importantly, there was a difference of α-inhibitor use between non-SpaceOAR and SpaceOAR groups at the end of SBRT and at 1.5-, 3-, and 6-months follow up (86% vs. 53% [p = 0.002], 83% vs. 53% [p = 0.005], 72% vs. 49% [p = 0.038], respectively).

CONCLUSION

LUTS after SBRT remains a significant problem for men undergoing treatment for prostate cancer. LUTS affects men during and up to 6-months following SBRT. Owing to these increased LUTS, preemptive minimally invasive solutions and their mechanisms of protection, including the SpaceOAR, should be further investigated.

Mobile mammography in New York City: analysis of 32,350 women utilizing a screening mammogram program

Mobile mammography vans (mammovans) may help close the gap to access of breast cancer screening by providing resources to underserved communities. Minimal data exists on the populations served, the ability of mammovans to reach underserved populations, and the outcomes of participants. We sought to determine the demographic characteristics, number of breast cancers diagnosed, and number of women who used the American Italian Cancer Foundation (AICF) Mobile, No-Cost Breast Cancer Screening Program within the five boroughs of New York City. Data were collected by the AICF from 2014 to 2019 on a voluntary basis from participants at each screening location. Women aged 40 to 79 years who had not had a mammogram in the previous 12 months were invited to participate. Each participant underwent a clinical breast exam by a nurse practitioner followed by a screening mammogram. Images were read by a board-certified radiologist contracted by the AICF from Multi Diagnostic Services. There were 32,350 participants in this study. Sixty-three percent reported an annual household income ≤$25,000, and 30% did not have health insurance. More than half of participants identified as either African American (28%) or Hispanic (27%). Additional testing was performed for 5359 women found to have abnormal results on screening. In total, 68 cases of breast cancer were detected. Breast cancer disparities are multifactorial, with the greatest factor being limited access to care. Mobile, no-cost mammogram screening programs show great promise in helping to close the gap to screening access.

Benefit of adjuvant chemotherapy in node-negative T1a versus T1b and T1c triple-negative breast cancer

PURPOSE

National comprehensive cancer network guidelines recommend delivery of adjuvant chemotherapy in node-negative triple-negative breast cancer (TNBC) if the tumor is > 1 cm and consideration of adjuvant chemotherapy for T1b but not T1a disease. These recommendations are based upon sparse data on the role of adjuvant chemotherapy in T1a and T1b node-negative TNBC. Our objective was to clarify the benefits of chemotherapy for patients with T1N0 TNBC, stratified by tumor size.

METHODS

We performed a retrospective analysis of survival outcomes of TNBC patients at two academic institutions in the United States from 1999 to 2018. Primary tumor size, histology, and nodal status were based upon surgical pathology. The Kaplan-Meier plot and 5-year unadjusted survival probability were evaluated.

RESULTS

Among 282 T1N0 TNBC cases, the status of adjuvant chemotherapy was known for 258. Mean follow-up was 5.3 years. Adjuvant chemotherapy was delivered to 30.5% of T1a, 64.7% T1b, and 83.9% T1c (p < 0.0001). On multivariable analysis, factors associated with delivery of adjuvant chemotherapy were tumor size and grade 3 disease. Improved overall survival was associated with use of chemotherapy in patients with T1c disease (93.2% vs. 75.2% p = 0.008) but not T1a (100% vs. 100% p = 0.3778) or T1b (100% vs. 95.8% p = 0.2362) disease.

CONCLUSION

Our data support current guidelines indicating benefit from adjuvant chemotherapy in node-negative TNBC associated with T1c tumors but excellent outcomes were observed in the cases of T1a and T1b disease, regardless of whether adjuvant chemotherapy was delivered.

285 Breaking through the resistance of breast cancer to immune checkpoint blockers in a unique mouse model of HR+ disease

Background

Hormone receptor (HR)+ breast cancer (BC) causes most BC-related deaths in the US.1 Standard treatment for non-metastatic disease involves surgery plus adjuvant hormonotherapy. However, approximately 50% of patients ultimately relapse and require additional lines of treatment including chemotherapy, which is unfortunately associated with limited clinical benefits and severe toxicity. In HR+ BC patients, the efficacy of immunotherapy has also been disappointing so far. Indeed, objective responses to PD-1 blockade with pembrolizumab in women with HR+ BC have been in the range of 5–10%, with no clear advantage on survival. Thus, resistance to PD-1 blockers constitutes a major obstacle towards the implementation of immunotherapy in HR+ BC patients.

Methods

To obtain insights into the immunological alterations accompanying disease relapse in HR+ BC exposed to PD-1 blockade, we harnessed a unique endogenous model of BC driven in immunocompetent mice by progesterone and a carcinogen. This model recapitulates key aspects of human luminal B BC, including a relatively ´cold´ microenvironment, hence limited sensitivity to PD-1 blockade.2 We undertook an in-depth characterization of the tumors (by DNAseq and RNAseq) and systemic (by flow cytometry on the splenic compartment) immune microenvironment of C57BL/6 female mice bearing tumors that recovered normal growth after PD-1 treatment.

Results

There was no clear difference after PD-1 blockade at the systemic level in the myeloid, or lymphoid compartments; or in the activation of T cells, nor their capacity to degranulate upon ex vivo stimulation. Whole exome sequencing showed a higher mutational burden in PD-1 treated tumors after relapse. At the gene expression level, unsupervised analysis showed a clustering independent of the treatment groups, probably due to the heterogeneity of the model. Targeted pathway analysis with supervised clustering showed however differences in immune pathways that are currently further investigated, and results will be available shortly.

Conclusions

Breaking through resistance of HR+ tumors to PD-1 blockers can direct strategies to overcome resistance in HR+ BC patients, the majority of BC patients. If successful, this can inform therapeutic approaches to enable superior therapeutic responses in patients with HR+ BC, hence significantly reducing BC-related deaths.

References

Siegel RL, Miller KD, Jemal A. Cancer statistics, 2020. CA Cancer J Clin 2020;70:7–30.

Buque A, Bloy N, Perez-Lanzon M, Iribarren K, Humeau J, Pol JG, Levesque S, Mondragon L, Yamazaki T, Sato A, Aranda F, Durand S, Boissonnas A, Fucikova J, Senovilla L, Enot D, Hensler M, Kremer M, Stoll G, Hu Y, Massa C, Formenti SC, Seliger B, Elemento O, Spisek R, Andre F, Zitvogel L, Delaloge S, Kroemer G, Galluzzi L. Immunoprophylactic and immunotherapeutic control of hormone receptor-positive breast cancer. Nat Commun 2020;11:3819.

Ethics Approval

This study was approved by Weill Cornell Medical College’s Ethics Board; approval number 2018–0053.

733 Immunological mechanisms of resistance to CDK4/CDK6 inhibitors in breast cancer

Background

Hormone receptor+ (HR+) breast cancer (BC) is the most frequent cause of BC-related deaths. CDK4/6 inhibitors (CDK4/6i) combined with endocrine therapy (ET) emerged as an effective approach for metastatic HR+ BC. However, >60% women with HR+ BC receiving CDK4/6i+ET ultimately relapse, potentially due to activation of poorly characterized immunosuppressive pathways in the tumor microenvironment (TME).1 Thus, strategies breaking resistance to CDK4/6i+ET in women with HR+ BC are urgently awaited. Radiation therapy (RT) mediates immunostimulatory effects that only partially overlap with those of CDK4/6i+ET,2 standing out as a promising therapeutic partner. Consistent with this notion, we recently demonstrated that RT followed by the CDK4/6i palbociclib + ET (RT-P+ET) enables superior tumor control in various immunocompetent mouse models of HR+ BC.3 These findings have inspired the design of a randomized phase II clinical trial testing P+ET vs. RT-P+ET in patients with oligometastatic HR+ BC (CIMER, NCT04563507). In this context, we set out to dissect the immunological mechanisms underlying sensitivity vs. resistance to treatment in HR+ BC exposed to P+ET vs. RT-P+ET.

Methods

To dissect the impact of these treatments on immune contexture in HR+ BC, we performed single-cell RNAseq on CD45+ cells infiltrating MPA/DMBA (M/D)-driven carcinomas established in immunocompetent mice (a unique model of luminal B BC), coupled to bulk RNAseq, bioinformatic analysis on public patient datasets, functional studies on ex vivo immune cells and efficacy studies.

Results

We observed that (1) RT and P+ET alone mediate partial efficacy correlating with accumulation of immunosuppressive TREG and IL17A-producing γδ T cells, respectively, (2) γδ T cell depletion improves the efficacy of P+ET, (3) RT-P+ET mediates superior (but incomplete) tumor control, which is partially offset by CD4+/CD8+ T cell co-depletion and correlates with limited infiltration by γδ T cells and TREGS, but accumulation of PD-L1 expressing myeloid cells and M2-polarized TREM2+ macrophages, which have been ascribed robust immunosuppressive effects in multiple settings4; and (4) that PD-1 blockage does not ameliorate the therapeutic effects of RT-P+ET (not shown), pointing to TREM2+ macrophages as to the main culprits for resistance in this setting.

Conclusions

Our observations suggest that γδ T cells and TREM2+ macrophages support the resistance of HR+ BC to CDK4/6i and RT-CDK4/6i, and hence constitute potential targets to delay disease progression.

References

Pandey et al. Molecular mechanisms of resistance to CDK4/6 inhibitors in breast cancer: a review. Int J Cancer 2019;145(5):1179–1188.

Rodriguez-Ruiz et al. Immunological impact of cell death signaling driven by radiation on the tumor microenvironment. Nat Immunol 2020;21(2):120–134.

Petroni et al. Radiotherapy delivered before CDK4/6 inhibitors mediates superior therapeutic effects in ER + Breast cancer. Clin Cancer Res 2021;27(7):1855–1863.

Xiong et al. A gene expression signature of TREM2 hi macrophages and γδ T cells predicts immunotherapy response. Nat Commun 2020;11(1):5084.

Ethics Approval

Animal experiments were approved by the Institutional Animal Care and Use Committee (IACUC) of Weill Cornell Medical College (n° 2019–2022).

Phase I Trial of Cemiplimab, Radiotherapy, Cyclophosphamide, and Granulocyte Macrophage Colony-Stimulating Factor in Patients with Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma

LESSONS LEARNED

Cemiplimab in combination with radiation therapy, cyclophosphamide, and granulocyte macrophage colony-stimulating factor did not demonstrate efficacy above what can be achieved with other PD-1 inhibitor monotherapies in patients with refractory and metastatic head and neck squamous cell carcinoma. The safety profile of cemiplimab combination therapy was consistent with previously reported safety profiles of cemiplimab monotherapy. No new safety signal was observed.

BACKGROUND

Refractory and metastatic (R/M) head and neck squamous cell carcinoma (HNSCC) generally does not respond to PD-1 inhibitor monotherapy. Cemiplimab is a human anti-PD-1 monoclonal antibody. An expansion cohort enrolled patients with R/M HNSCC in a phase I study combining cemiplimab plus radiation therapy (RT), cyclophosphamide, and granulocyte macrophage colony-stimulating factor (GM-CSF).

METHODS

Patients with R/M HNSCC refractory to at least first-line therapy and for whom palliative RT is clinically indicated received cemiplimab plus RT, cyclophosphamide, and GM-CSF. The co-primary objectives were the safety, tolerability, and efficacy of cemiplimab plus RT, cyclophosphamide, and GM-CSF in 15 patients with R/M HNSCC.

RESULTS

Fifteen patients were enrolled. Patients discontinued treatment due to progression of disease. The most common treatment-emergent adverse events (TEAEs) of any grade were fatigue (40.0%), constipation (26.7%), and asthenia, dyspnea, maculo-papular rash, and pneumonia (each 20%). The only grade ≥3 TEAE that occurred in two patients was pneumonia (13.3%). By investigator assessment, there was one partial response (6.7%); disease control rate was 40.0% (95% confidence interval [CI], 16.3-67.7; five patients with stable disease); seven patients had progressive disease, and two were not evaluable. Median progression-free survival by investigator assessment was 1.8 months (95% CI, 1.7-4.7).

CONCLUSION

The regimen demonstrated tolerability but not efficacy above that which can be achieved with anti-PD-1 inhibitor monotherapy for R/M HNSCC.

Abstract IA003: Radiotherapy effects on tumor microenvironment

Radiation therapy (RT) exerts multiple effects on the tumor and its microenvironment, affecting immunity, metabolism and the microbiome (Heather M. McGee et al. Clin Cancer Res 2019;25:2969-2974). Radiation has profound and sustained effects on non-malignant tissue, including epithelial to mesenchymal transition (EMT) and carcinogenesis. Seminal experiments from Barcellos-Hoff' s lab originally demonstrated the capacity of RT to induce EMT of non-malignant epithelial cells (Andarawewa, KL et al: Cancer Res 2007; 67: (18). September 15, 2007). Burma et al demonstrated in an in vivo model of gliomas engineered after loss of one allele of Trp53 and Pten, that mice were highly susceptible to radiation-induced gliomagenesis in a linear energy transfer (LET)-dependent manner, possibly dependent on the increasing degree of irreparable DNA breaks with increasing LET (Todorova PK et al Cancer Res 2007; 67: (18). September 15, 2007). Interestingly, the histopathology of RT-induced high grade gliomas in this model mimics that of human glioblastoma, with similar patterns of necrosis, pseudo-palisading and nuclear atypia. This effect has translational implications, in view of the fact that the adjacent irradiated brain after standard post-operative RT to GBM is the most common site of recurrence (Gupta K and Burns TC: Frontiers in Oncology, 2018). Radiation is a powerful inducer of immunogenic cell death (ICD) of cancer cells, by releasing of DAMPs such as high mobility group box protein 1 (HMGB1), ATP and translocation of calreticulin to cell surface. In response to DNA damage, cytosolic DNA released from the nucleus mitochondria activates sensors like cGAS/STING, leading to an increase in IFNβ, that recruits and activates BAFT3+ dendritic cells, crucial agents for cross-presentation and cross-priming of CD8+ T cells. Radiation also increases the trafficking of activated CD8+ T cells by releasing CXCL16, a chemokine that binds to CXCR6 (Matsumura et al., J Immunol 181:3099-3107 2008). Recent evidence has demonstrated how as part of DNA damage response to RT, tumor mutations are expressed and can generate neoantigens that contribute to sustained immune responses in patients (Nature Medicine, 2018; 24;12:1845). Consequently, RT can recruit both the innate and adaptive immune response and, in combination with immune checkpoint blockade (ICB) can convert the irradiated tumor into an in situ vaccine. The choice of technical parameters like radiation dose rate, dose and fractionation and the type of field chosen, all impact on the success of RT and immunotherapy combinations, as demonstrated by impairment of immune response when nodal regions are included in the field treated by RT and ICB (Marciscano A et al: Clin Cancer Res: 4(20) October 15, 2018). The widespread access to radiotherapy centers and the ease to include a standard modality like RT in clinical trials have have rendered it one of the tools of modern immunotherapy of cancer, by exploiting RT effects on tumor and TME, beyond its classical cytocidal potential.

Citation Format: Silvia Formenti. Radiotherapy effects on tumor microenvironment [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr IA003.

Perspectives in immunotherapy: meeting report from the "Immunotherapy Bridge" (December 4th-5th, 2019, Naples, Italy)

Over the last few years, numerous clinical trials and real-world experience have provided a large amount of evidence demonstrating the potential for long-term survival with immunotherapy agents across various malignancies, beginning with melanoma and extending to other tumours. The clinical success of immune checkpoint blockade has encouraged increasing development of other immunotherapies. It has been estimated that there are over 3000 immuno-oncology trials ongoing, targeting hundreds of disease and immune pathways. Evolving topics on cancer immunotherapy, including the state of the art of immunotherapy across various malignancies, were the focus of discussions at the Immunotherapy Bridge meeting (4-5 December, 2019, Naples, Italy), and are summarised in this report.

Capturing Acquired Wisdom, Enabling Healthful Aging, and Building Multinational Partnerships Through Senior Global Health Mentorship

The undeniable benefit of mentorship by experience senior mentors can meaningfully increase the breadth of their experience and contributions to society as well as address the dire inequality in global health. This model captures wisdom lost to retirement, enables opportunities for purposeful lifespan, underpins sustainable health care systems, and has the potential for building multinational partnerships.

Radiosurgery and Immunotherapy in the Treatment of Brain Metastases

Radiation therapy represents a mainstay of treatment for patients with brain metastases. Recently, the widespread adoption of immune checkpoint blockade has led to keen interest in treating cancers with checkpoint inhibitors in place of, or as an adjunct to, traditional chemotherapy. However, with the exception of melanoma, immune checkpoint blockade in solid tumors has failed to achieve significant brain control in patients with brain metastases. The possibility of combining immune checkpoint blockade with radiation for the treatment of brain and other metastases represents an exciting new strategy that is in its early stages of investigation. Success with this combinatorial strategy has the potential to result in enhanced rates of brain control, less brain exposure to radiation, and improved cognitive outcomes. In this review, we discuss the mechanisms behind this synergy, describe its limitations, and suggest ways to move the field forward.

Harnessing radiation to improve immunotherapy: better with particles?

The combination of radiotherapy and immunotherapy is one of the most promising strategies for cancer treatment. Recent clinical results support the pre-clinical experiments pointing to a benefit for the combined treatment in metastatic patients. Charged particle therapy (using protons or heavier ions) is considered one of the most advanced radiotherapy techniques, but its cost remains higher than conventional X-ray therapy. The most important question to be addressed to justify a more widespread use of particle therapy is whether they can be more effective than X-rays in combination with immunotherapy. Protons and heavy ions have physical advantages compared to X-rays that lead to a reduced damage to the immune cells, that are required for an effective immune response. Moreover, densely ionizing radiation may have biological advantages, due to different cell death pathways and release of cytokine mediators of inflammation. We will discuss results in esophageal cancer patients showing that charged particles can reduce the damage to blood lymphocytes compared to X-rays, and preliminary in vitro studies pointing to an increased release of immune-stimulating cytokines after heavy ion exposure. Pre-clinical and clinical studies are ongoing to test these hypotheses.

Preoperative radiotherapy for high-risk prostate cancer (PORT-PC) trial

TPS137

Background: Prostatectomy has become the most common treatment for high-risk prostate cancer. After prostatectomy, risk features for local recurrence include extra-capsular extension and/or seminal vesicle invasion (pT3 disease) and positive surgical margins. Post-operative radiotherapy is recommended for patients with pT3 disease, positive margins and/or Group Grade 4-5 and has been shown to reduce the risk of recurrence. In planning adjuvant radiotherapy, the clinical target volume is the prostate bed which is difficult to delineate once the prostate has been surgically removed and can be overestimated by following the location of surgical clips. As such, controversy exists as to the optimal target volume. Guidelines suggest including a significant portion of the posterior and inferior aspects of the bladder, and anterior aspect of the rectum exposing a significant amount of normal tissue to high dose radiation. Pre-operative radiotherapy potentially offers the following advantages: 1) reduced radiation dose to normal tissues; 2) ability to utilize stereotactic body radiotherapy (SBRT) with real-time MRI guidance 3) patient convenience with less fractions and 4) radiobiologic advantage of high dose per fraction treatment delivery. Methods: This is a modified dose escalation trial for patients with high-risk prostate cancer defined as cT3 on MRI or Group Grade 4-5 disease. Patients will sequentially undergo 1) placement of a rectal SpaceOAR, 2) SBRT on the ViewRay MRIdian linear accelerator and 3) prostatectomy. As a modified dose escalation study, patients will be accrued starting at 5 Gy x 5 (up to 8 Gy x 5) with 3 patients per cohort with Grade 4 or 5 gastrointestinal (GI) and/or genitourinary (GU) adverse event related to preoperative radiotherapy as an unacceptable dose limiting toxicity.The primary endpoint is that a patient can undergo a radical prostatectomy after SBRT without a post-operative GI or GU grade 4 or 5 toxicity within 30 days related to preoperative radiotherapy. Secondary objectives include assessment of acute toxicity and quality of life scores. Exploratory analyses include analysis of tumor and normal biopsied and resected tissue and serum markers and interpretation of pre- and post-SBRT MRIs. Clinical trial information: NCT03663218.

Development and Implementation of a Telemedicine Platform for Radiation Oncology Training and Peer Review

Background: Telemedicine has been posited as a potential means of bolstering radiation therapy delivery in developing nations. World Aid Exchange (WaidX) is an innovative intercontinental telemedicine platform oriented to oncology specialties. This platform, devoted to reducing the digital divide on health practice, provides telecommunication services between health care facilities in developed and developing countries. It conveys the ability to safely share radiologic images and patient medical records for diagnostic and care purposes. It was successfully piloted in Mwanza, Tanzania in 2015. Since then, it has been implemented in varied settings such as Ethiopia, Djibouti and Brazil. After conducting a site visit and a focused needs assessment, we recognized the need for teleconferencing with the Radiation Department of National Center of Oncology, Yerevan, Armenia, to share expertises in general patient management and contouring and planning for radiotherapy. Aim: To develop a TeleRadiotherapy platform that enables: 1: Conference calling for tumor boards to review radiotherapy plans, discuss disease management and conduct remote quality control 2: Real-time sharing of diagnostic images to guide clinical decision making 3: E-contouring activity performed by parties in Yerevan and New York on radiographic images, with minimization of time lag in contouring 4: Generation of a database for clinical data (i.e., radiation dose, toxicity, disease stage) that serves as a departmental registry and a tool for future research use 5: Access to lectures delivered by physicians, nurses, therapists and physicists both in Yerevan and New York on varied aspects of radiotherapy Methods: The initiative was funded through a competitive grant established within the Department of Radiation Oncology at Cornell. The TeleRadiotherapy system is comprised of 2 physical units, equipped to support networking and telephony integration. An application was used to establish a simplified direct connection between mobile phones in New York and fixed phone extensions in Yerevan. A customized version of Veyon was used for remote connection to a contouring station. Zoom was used to establish the teleconference. Remote operators in Weill Cornell Medicine were trained for using the system. Results: The first teleradiotherapy interaction between Yerevan and New York occurred on February 7th, 2018. Demonstration of contouring on the Oncentra treatment planning system in Yerevan revealed ease of use. The brush tool displayed less drag time than the point-by-point contouring tools. Diagnostic images were easily shared without compromise of the image resolution. Conference call quality was high. This conference has opened a series of biweekly chart rounds, between the two institutions. Conclusion: Teleradiotherapy is feasible with excellent voice quality, image sharing capability and real-time contouring. The database is under construction. We are developing a new model for learning, training and collaboration in radiotherapy using WaidX, to enable rapid knowledge and technology transfer for a more equitable access to high-quality cancer care worldwide.

The Future of Global Radiation Oncology As Part of Accurate, Precision Cancer Medicine

Background: When global health and cancer care are discussed, it is usually in the context of underserved communities, inadequate resources, standards of care below that in the developed world, loss of talented individuals to upper-income countries and the inability to recruit and retain a robust regional workforce. While such conditions may now exist, they are by no means “guaranteed” to be so in the future. Aim: To consider a visionary future for the radiation sciences to encourage investment by individuals in their careers and countries in their cancer care resources such that the current resource-limited facilities will be on the leading edge of accurate, precision radiation medicine. Such a change in perspective can greatly impact recruiting and retaining expertise. Methods: As part of building a visionary strategic plan for radiation oncology and the radiation sciences for the next few decades, a personal opinion paper was prepared by authors from the US National Cancer Institute, Conseil Européen pour la Recherche Nucléaire (CERN)/European Organization for Nuclear Research and the International Conference on Translational Research in Radio-Oncology/Physics for Health in Europe. Considering the critical role for global involvement in the future of radiation sciences, the paper provides a path forward via “win-win” sustainable partnerships formed by current resource-limited and resource-rich countries, as envisioned by the International Cancer Expert Corps ( www.iceccancer.org ). Results: The manuscript “ Accurate, precision radiation medicine: a meta-strategy for impacting cancer care, global health, nuclear policy, and mitigating radiation injury from necessary medical use, space exploration and potential terrorism” is in press. A figure (the Radiation Rotary) illustrates that there are a number of crossroads facing the radiation sciences best addressed as part of a rotary. Four sets of issues are illustrated: 1) cancer care with radiation therapy as both technology and biology, 2) global collaboration in technology development ranging from improved linear accelerators for resource-challenged environments to particle therapy for highly specialized uses, 3) nuclear policy, from energy to the potential for nuclear terrorism and conflagration, and 4) mitigating radiation injury including enabling long-term space exploration, helping reduce the fear of radiation and producing drugs to mitigate radiation injury. Conclusion: Many of these technology, research and development issues must involve LMICs. This is in addition to understanding the differences between upper- and lower-income regions in cancer biology and the environment, including infectious etiologies, diet and the microbiome. The talent and capability of radiation oncologists and related professionals within LMICs are essential to global health and economic development and provide incentives and unique opportunities for world-leading careers and contributions. Disclaimer: The content is the personal opinion of the authors and not their organizations

Abstract B05: Adenosine generation limits the ability of radiation therapy to induce antitumor immunity by abrogating recruitment and activation of CD103+ DCs

Localized radiation therapy (RT) can act as a powerful adjuvant to immunotherapeutic strategies by triggering anti-tumor immune responses to poorly immunogenic tumors. Radiation of tumor cells induces a dose-dependent release of ATP, a molecule that when released in the tumor microenvironment (TME) triggers recruitment and activation of dendritic cells (DCs), including CD103+ DCs recently identified as the key DC subset responsible for cross-presentation of tumor-derived antigens to CD8+ T cells. However, rapid hydrolysis of extracellular ATP by ecto-enzymes CD39 and CD73 results in a local accumulation of immunosuppressive adenosine that inhibits DC activation and CD8+ T cell effector functions and promotes regulatory T cells (Tregs). By blocking CD73 in conjunction with local tumor RT, we tested the hypothesis that adenosine generation limits the ability of RT to trigger anti-tumor immunity.

Wild type (WT) or BATF3-/- mice (CD103+ DC-deficient) were inoculated s.c. with TSA tumor cells (day 0) and assigned to treatment with: (1) control Ab; (2) anti-CD73 Ab (100 μg) (3) RT (20 Gy); (4) RT + anti-CD73 Ab. Antibodies were administered i.p. on day 11, 14, 17 and 20. RT was given locally as single 20 Gy dose on day 12. On day 18, tumors were analyzed by flow cytometry for DC and T cell infiltration. Mice were monitored for tumor progression. Bone marrow-derived DCs (BMDCs) isolated from WT mice (&gt;90% CD103+) were labeled with CFSE and intravenously injected in BATF3-/- recipient mice. Tumors were harvested after 48h and analyzed by flow cytometry for infiltration of CFSE+ DCs.

In irradiated but not mock-treated mice, anti-CD73 Ab resulted in increased infiltration of CD103+DCs (8.9±2.6% of DCs in RT+anti-CD73 v. 3.5±2.8% of DCs in RT, p&lt;0.05) expressing elevated levels of activation marker CD86 compared to mice treated with RT alone. This change was associated with improved CD8+T cell/Treg ratio (5±2.8 in RT+anti-CD73 v. 0.8±0.2 in RT). Importantly, CD73 blockade had no effect by itself but improved significantly radiation-induced tumor control (Tumor size at day 57 post inoculation: 385±525 mm3 in RT+anti-CD73 v. 1036±727 mm3 in RT). Consistent with the hypothesis that CD103+ DCs are essential for anti-tumor responses, the therapeutic effect of RT+CD73 blockade was abrogated in BATF3-/- mice. Moreover, CD73 blockade facilitated recruitment of adoptively transferred CD103+ BMDCs in irradiated tumors in BATF3-/- mice.

Our data support the hypothesis that adenosine generated following RT plays a key role in hindering development of anti-tumor immune responses and identify, as a mechanism of this effect, an abrogated infiltration and activation of CD103+ DCs. Blockade of adenosine generation by anti-CD73 treatment constitutes a promising strategy to enhance radiation-induced anti-tumor immunity.

Citation Format: Erik Wennerberg, Silvia Formenti, Sandra Demaria. Adenosine generation limits the ability of radiation therapy to induce antitumor immunity by abrogating recruitment and activation of CD103+ DCs [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B05.

Practice patterns and outcomes for patients with node-negative hormone receptor-positive breast cancer and intermediate 21-gene Recurrence Scores

BACKGROUND

The recommendation for chemotherapy in early-stage breast cancer patients has been refined by the 21-gene Recurrence Score. However, uncertainty remains whether patients in the Intermediate Risk category benefit from chemotherapy.

METHODS

We analyzed female patients from the National Cancer Database from 2006 to 2012 who had pT1c-T2N0M0 breast cancer, were ER/PR-positive and HER2-negative, received endocrine therapy, and had a 21-gene Recurrence Score from 11 to 25. We performed univariate and multivariate logistic regression analyses to see what impacted chemotherapy receipt. We compared overall survival using Kaplan-Meier curves and the log-rank test. A multivariable Cox proportional hazards regression model was used to assess what variables impacted overall survival.

RESULTS

Of 21,991 patients who met all inclusion and exclusion criteria, 4646 (21.1%) received chemotherapy and 17,345 (78.9%) did not. Chemotherapy was more often received by patients who were younger (adjusted odds ratios (aORs) compared to age < 40 years, 0.48 for 40s, 0.34 for 50s, 0.20 for 60s, 0.10 for 70s, and 0.07 for 80+), had private insurance vs Medicare (aOR = 1.37), were from metro vs urban counties (aOR = 1.15), and were treated in community cancer centers vs academic programs (aOR = 1.26), and those with tumors of higher grade (grade 2 vs 1, aOR = 1.72; grade 3 vs 1, aOR = 3.76), higher tumor stage (pT2 vs pT1c, aOR = 1.62), or presence of lymphovascular invasion (LVI) (aOR = 1.41). At a median follow-up of 46.4 months, there was no significant difference in overall survival between patients who received chemotherapy vs those who did not (5-year estimated overall survival, 97.4% vs 97.8%, p = 0.89). On multivariable analysis, worse overall survival was associated with Black race, treatment at a community program, Medicaid, high-grade tumors, pT2 vs pT1c, higher Charlson-Deyo score, and no radiotherapy. Utilization trends showed that chemotherapy receipt in these patients has been decreasing from 25.8% in 2010 to 18.4% in 2013 (p < 0.001).

CONCLUSIONS

In these patients where the benefit of chemotherapy remains uncertain, current practices see chemotherapy more likely to be used in patients with younger age, higher pathologic T stage, higher grade tumors, and LVI. No apparent difference was seen in overall survival between those who received chemotherapy and those who did not.

Therapeutic effect of local Interleukin-15 with radiotherapy in breast cancer

158

Background: Interleukin (IL)-15 is a key regulator of T cell homeostasis with activity in cancer and a favorable toxicity profile compared to IL-2. IL-15 stimulates the proliferation and effector differentiation of CD8+T cells, and the proliferation and activation of natural killer (NK) cells. We observed IL-15 upregulation by gene arrays in radiotherapy (RT)-treated TSA mouse breast cancer, suggesting that it may play a role in RT-induced anti-tumor immunity. However, the upregulation was modest prompting us to test the hypothesis that administration of IL-15 may enhance in situ vaccination by RT. Methods: BALB/c mice with established poorly immunogenic TSA tumors were sham-treated, treated with tumor-targeted RT (8GyX3 days), IL-15 given peri-tumorally (2 ug/mouse/day for 10 days) starting on the first day of RT, and RT+IL-15, and monitored for tumor growth and survival. Tumor infiltrating lymphocytes (TIL) were analyzed by flow cytometry and immunostaining. In some experiments, Batf3-/-mice were used as tumor recipient. Results: IL-15 by itself was ineffective, but it significantly increased tumor control by RT (p=0.0007, RT versus RT+IL-15) leading to complete responses in 50% of the mice, most of them durable. Analysis of TILs showed significantly increased NK cells (CD45+ CD3- DX5+) in tumors treated with RT+IL-15 (p<0.0004 versus sham-treated; p<0.02 versus RT). NK cells were also more activated as indicated by expression of CD122 and CD137. Depletion of NK cells completely abrogated the therapeutic effect of the combination, while CD8 T cell depletion reduced tumor control and rate of complete regression. Interestingly, Batf3-/- mice, which lack CD103+ DCs, showed reduced response to RT+IL-15 compared to WT mice. Conclusions: Data suggest that local IL-15 with RT is an effective strategy to induce anti-tumor immunity to poorly immunogenic breast cancer. NK cells are critical mediators of the response, and may act by both killing tumor cells and promoting priming of CD8 T cells. Experiments are ongoing to determine the mechanisms of durable complete responses. <footer>Acknowledgments: IL-15 was provided by NCI BRB. Garcia-Martinez E was supported by GEICAM grant.</footer>

Smart Radiation Therapy Biomaterials

Radiation therapy (RT) is a crucial component of cancer care, used in the treatment of over 50% of cancer patients. Patients undergoing image guided RT or brachytherapy routinely have inert RT biomaterials implanted into their tumors. The single function of these RT biomaterials is to ensure geometric accuracy during treatment. Recent studies have proposed that the inert biomaterials could be upgraded to "smart" RT biomaterials, designed to do more than 1 function. Such smart biomaterials include next-generation fiducial markers, brachytherapy spacers, and balloon applicators, designed to respond to stimuli and perform additional desirable functions like controlled delivery of therapy-enhancing payloads directly into the tumor subvolume while minimizing normal tissue toxicities. More broadly, smart RT biomaterials may include functionalized nanoparticles that can be activated to boost RT efficacy. This work reviews the rationale for smart RT biomaterials, the state of the art in this emerging cross-disciplinary research area, challenges and opportunities for further research and development, and a purview of potential clinical applications. Applications covered include using smart RT biomaterials for boosting cancer therapy with minimal side effects, combining RT with immunotherapy or chemotherapy, reducing treatment time or health care costs, and other incipient applications.

Enterococcus hirae and Barnesiella intestinihominis Facilitate Cyclophosphamide-Induced Therapeutic Immunomodulatory Effects

The efficacy of the anti-cancer immunomodulatory agent cyclophosphamide (CTX) relies on intestinal bacteria. How and which relevant bacterial species are involved in tumor immunosurveillance, and their mechanism of action are unclear. Here, we identified two bacterial species, Enterococcus hirae and Barnesiella intestinihominis that are involved during CTX therapy. Whereas E. hirae translocated from the small intestine to secondary lymphoid organs and increased the intratumoral CD8/Treg ratio, B. intestinihominis accumulated in the colon and promoted the infiltration of IFN-γ-producing γδT cells in cancer lesions. The immune sensor, NOD2, limited CTX-induced cancer immunosurveillance and the bioactivity of these microbes. Finally, E. hirae and B. intestinihominis specific-memory Th1 cell immune responses selectively predicted longer progression-free survival in advanced lung and ovarian cancer patients treated with chemo-immunotherapy. Altogether, E. hirae and B. intestinihominis represent valuable "oncomicrobiotics" ameliorating the efficacy of the most common alkylating immunomodulatory compound.