Pharmacologic inhibition of ataxia telangiectasia and Rad3-related (ATR) in the treatment of head and neck squamous cell carcinoma.

Head and neck squamous cell carcinoma (HNSCC) poses significant treatment challenges, with high recurrence rates for locally advanced disease despite aggressive therapy typically involving a combination of surgery, radiation therapy, and/or chemotherapy. HNSCCs commonly exhibit reduced or absent TP53 function due to genomic alterations or human papillomavirus (HPV) infection, leading to dependence on the S- and G2/M checkpoints for cell cycle regulation. Both of these checkpoints are activated by Ataxia Telangiectasia and Rad3-related (ATR), which tends to be overexpressed in HNSCC relative to adjacent normal tissues and represents a potentially promising therapeutic target, particularly in combination with other treatments. ATR is a DNA damage signaling kinase that is activated in response to replication stress and single-stranded DNA breaks, such as those induced by radiation therapy and certain chemotherapies. ATR kinase inhibitors are currently being investigated in several clinical trials as part of the management of locally advanced, recurrent, or metastatic HNSCC, along with other malignancies. In this review article, we summarize the rationale and preclinical data supporting incorporation of ATR inhibition into therapeutic regimens for HNSCC.

IRF1 Inhibits Antitumor Immunity through the Upregulation of PD-L1 in the Tumor Cell.

Multiple studies have associated the transcription factor IRF1 with tumor-suppressive activities. Here, we report an opposite tumor cell-intrinsic function of IRF1 in promoting tumor growth. IRF1-deficient tumor cells showed reduced tumor growth in MC38 and CT26 colon carcinoma and B16 melanoma mouse models. This reduction in tumor growth was dependent on host CD8+ T cells. Detailed profiling of tumor-infiltrating leukocytes did not show changes in the various T-cell and myeloid cell populations. However, CD8+ T cells that had infiltrated IRF1-deficieint tumors in vivo exhibited enhanced cytotoxicity. IRF1-deficient tumor cells lost the ability to upregulate PD-L1 expression in vitro and in vivo and were more susceptible to T-cell-mediated killing. Induced expression of PD-L1 in IRF1-deficient tumor cells restored tumor growth. These results indicate differential activity of IRF1 in tumor escape.

Single-Institution Experience in 3D MRI-Based Brachytherapy for Cervical Cancer for 239 Women: Can Dose Overcome Poor Response?

PURPOSE: Recent Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology guidelines recommend that the dose to 90% (D90) of the high-risk clinical target volume (HRCTV) in cervical cancer be at least 85 Gy, with higher doses for poor response to radiation therapy. METHODS AND MATERIALS: A retrospective review of brachytherapy delivered at a single institution was evaluated for dosimetry and outcomes. Significance of tumor parameters on local control was evaluated with Kaplan-Meier and univariable and multivariable Cox regression analysis. Correlations were determined with a linear regression model. RESULTS: A total of 239 women underwent high-dose-rate brachytherapy for cervical cancer between 2007 and 2018 with evaluable dosimetry. Median follow-up was 28.6 months. The median prescribed dose was 27.5 Gy in 5 fractions, with a median HRCTV D90 of 83.9 Gy (range, 81.9-85.7 Gy), HRCTV volume of 31 cm3 (range, 14.9-121.9 cm3), and treatment time of 51 days (range, 36-83 days). Local control for the entire cohort at 5 years was 90.8%. Local control was worse with adenocarcinomas, HRCTV >40 cm3 at brachytherapy, requirement for a higher brachytherapy dose, and treatment >51 days. On multivariable analysis, local control was worse with adenocarcinoma (hazard ratio, 4.141; 95% confidence interval, 1.498-11.444; P = .006) and HRCTV >40 cm3 (hazard ratio, 3.640; 95% confidence interval, 1.316-10.069; P = .013). HRCTV EQD2 D90 > 85 Gy did not statistically improve outcomes for any subset. The 2-year progression-free survival for HRCTV >40 cm3 was 66.2% versus 84.1% if ≤40 cm3 (P < .001). Overall survival was predicted by HRCTV and overall treatment time in multivariable analysis. For women with HRCTV ≤40 cm3, overall survival at 2 years was 90.4% versus 68.5% if >40 cm3 (P < .001). CONCLUSION: Local control was excellent with magnetic resonance imaging-based planning in the entire cohort of patients. A poor response to external beam radiation (larger HRCTV) and adenocarcinoma histology predicted for worse local control despite association with higher brachytherapy prescription. Women with these risk factors face higher rates of extrapelvic progression and poorer overall survival.

Declining brachytherapy utilization for high-risk prostate cancer-Can clinical pathways reverse the trend?

PURPOSE: Although external beam radiation therapy (EBRT) plus a brachytherapy boost (BB) offers a 20% improvement in biochemical progression-free survival compared with dose-escalated EBRT alone for men with intermediate and high-risk prostate cancer, population studies show a concerning decline in BB utilization. METHODS: We modified our clinical pathway (CP) in January 2016 to indicate EBRT with BB as first-choice modality for high-risk prostate cancer, based on preliminary findings of Androgen Suppression Combined with Elective Nodal and Dose-Escalated Radiation Therapy. A retrospective review was performed on 659 patients with high-risk prostate cancer treated with definitive intent EBRT ± BB within a network of 19 sites between December 2011 and July 2017. χ2 test was used to determine changes in practice pattern before vs. after CP modification. RESULTS: Before CP modification, 25.2% of patients were planned for BB, compared with 45.4% afterward (p < 0.001). Among 23 nonbrachytherapist physicians, utilization of BB increased from 3.4% to 14.8% (p < 0.001) after CP modification. Among nine brachytherapists, utilization increased from 46.4% to 55.6% (p = 0.120). Among patients treated by a nonbrachytherapist who did not receive BB, the reason was physician preference in 59.7%, patient preference in 19.9%, and other in 20.4%. CONCLUSION: Based on recent evidence suggesting improved biochemical progression-free survival with use of BB for high-risk prostate cancer, we modified our CP, after which we observed increased use of a BB across a network, especially among physicians who do not perform brachytherapy. However, physician preference remains the most significant factor in the nonutilization of BB. New mechanisms are needed to overcome this barrier.

ATR kinase inhibitor AZD6738 potentiates CD8+ T cell-dependent antitumor activity following radiation.

DNA-damaging chemotherapy and radiation therapy are integrated into the treatment paradigm of the majority of cancer patients. Recently, immunotherapy that targets the immunosuppressive interaction between programmed death 1 (PD-1) and its ligand PD-L1 has been approved for malignancies including non-small cell lung cancer, melanoma, and head and neck squamous cell carcinoma. ATR is a DNA damage-signaling kinase activated at damaged replication forks, and ATR kinase inhibitors potentiate the cytotoxicity of DNA-damaging chemotherapies. We show here that the ATR kinase inhibitor AZD6738 combines with conformal radiation therapy to attenuate radiation-induced CD8+ T cell exhaustion and potentiate CD8+ T cell activity in mouse models of Kras-mutant cancer. Mechanistically, AZD6738 blocks radiation-induced PD-L1 upregulation on tumor cells and dramatically decreases the number of tumor-infiltrating Tregs. Remarkably, AZD6738 combines with conformal radiation therapy to generate immunologic memory in complete responder mice. Our work raises the possibility that a single pharmacologic agent may enhance the cytotoxic effects of radiation while concurrently potentiating radiation-induced antitumor immune responses.

Standardization of radiation therapy dose for locally advanced non-small cell lung cancer through changes to a lung cancer clinical pathway in a large, integrated comprehensive cancer center network.

PURPOSE: The results of Radiation Therapy Oncology Group (RTOG) 0617, which randomized patients with stages IIIA/IIIB non-small cell lung cancer (NSCLC) to definitive chemoradiation therapy to 60 Gy versus 74 Gy, demonstrated a detrimental survival impact with high-dose radiation therapy. We evaluated the impact of changes to a provider-driven clinical pathway (CP) guiding management of NSCLC on practice throughout our cancer center network. METHODS AND MATERIALS: In 2001, we implemented a CP for management of stage IIIA/IIIB NSCLC with definitive chemoradiation therapy. In 2013, the CP for NSCLC was amended (amendment 1) to allow a dose range of 60 to 74 Gy. The CP was amended (amendment 2) in January 2016 to specify a dose range of 60 to 70 Gy. Higher doses were considered off-pathway and subject to peer review. Data from decisions entered from 2012 to 2016 were obtained. RESULTS: From 2012 until publication of RTOG 0617 in February 2015, the median prescription dose was 66 Gy delivered in 1.8 to 2.1 Gy fractions. Doses ≤66 Gy were prescribed for 52% of patients. From February 2015 to September 2016, the median prescription dose was 60 Gy, and 91% of prescription doses were ≤66 Gy. After amendment 2, 99% of decisions were ≤66 Gy. Dose ≤66 Gy was associated with treatment following publication of 0617 (P < .001) and treatment after amendment 2 (P < .001). On multivariable analysis, treatment after amendment 2 was associated with dose ≤66 Gy (odds ratio, 9.9; 95% confidence interval, 5.2-19.0; P < .001). The percentage of lung receiving 20 Gy was lower following publication of 0617 (P < .001). There was no difference in the percentage of heart receiving 40 Gy. CONCLUSIONS: CPs eliminate variations in practice that lead to inferior outcomes. Recognizing that our CP for definitive treatment of patients with locally advanced NSCLC allowed heterogeneous dose prescriptions, we modified the CP based on the publication of RTOG 0617. We found that the CP was a tool to ensure patients receive evidence-based care across a large cancer center network.