Accelerated repopulation as a cause of radiation treatment failure in non-small cell lung cancer: review of current data and future clinical strategies

Hyperthermia Reduces Irradiation-Induced Tumor Repopulation in an In Vivo Pancreatic Carcinoma Model

Pancreatic cancer has a poor prognosis due to its aggressive nature and ability to metastasize at an early stage. Currently, its management is still a challenge because this neoplasm is resistant to conventional treatment approaches, among which is chemo-radiotherapy (CRT), due to the abundant stromal compartment involved in the mechanism of hypoxia. Hyperthermia, among other effects, counteracts hypoxia by promoting blood perfusion and thereby can enhance the therapeutic effect of radiotherapy (RT). Therefore, the establishment of integrated treatments would be a promising strategy for the management of pancreatic carcinoma. Here, the effects of joint radiotherapy/hyperthermia (RT/HT) on optimized chick embryo chorioallantoic membrane (CAM) pancreatic tumor models are investigated. This model enables a thorough assessment of the tumor-arresting effect of the combined approach as well as the quantitative evaluation of hypoxia and cell cycle-associated mechanisms by both gene expression analysis and histology. The analysis of the lower CAM allows to investigate the variation of the metastatic behaviors of the cancer cells associated with the treatments. Overall, this study provides a potentially effective combined strategy for the non-invasive management of pancreatic carcinoma.

Clinical outcomes and toxicities of locally advanced esophageal squamous cell carcinoma patients treated with early thoracic radiation therapy after induction chemotherapy

OBJECTIVE

The purpose of this study was to compare the clinical outcomes and toxicities between induction chemotherapy (IC) + chemo-radiotherapy (CRT) and CRT alone in patients with locally advanced esophageal squamous cell carcinoma (ESCC), to explore the appropriate thoracic radiotherapy (TRT) timing after IC and to identify prognostic factors.

METHODS

450 ESCC patients were included from September 2011 to December 2020, 238 of whom received IC/CRT. Propensity score matching was performed to balance potential confounders between the two groups. Multivariate Cox regression analysis was used to identify the independent prognostic factors.

RESULTS

Patients who received IC/CRT experienced improved overall survival (OS) (38.5 vs. 28.8 months) and progression-free survival (PFS) (41.0 vs. 22.0 months) before matching, with similar results after matching. In the IC/CRT group, early TRT had more favorable survival than late TRT both matching before and after. In subgroup analysis, early TRT combination concurrent chemotherapy had better OS and PFS than late TRT combination concurrent chemotherapy. In addition, early TRT had better survival benefits regardless of the N stage. Notably, the IC/CRT group and early TRT group had manageable toxicities reaction compared with CRT alone group and the late TRT group. The nomogram was developed to predict the OS and PFS based on multivariate analysis results. The C-index was 0.743 and 0.722, respectively.

CONCLUSION

IC/CRT and early TRT could yield satisfactory clinical outcomes and controllable toxicities in locally advanced ESCC. The IC plus early concurrent CRT might be a promising treatment strategy for improving further survival in ESCC.

Predicting personalised and progressive adaptive dose escalation to gross tumour volume using knowledge-based planning models for inoperable advanced-stage non-small cell lung cancer patients treated with volumetric modulated arc therapy

OBJECTIVES

Increased radiation doses could improve local control and overall survival of lung cancer patients, however, this could be challenging without exceeding organs at risk (OAR) dose constraints especially for patients with advanced-stage disease. Increasing OAR doses could reduce the therapeutic ratio and quality of life. It is therefore important to investigate methods to increase the dose to target volume without exceeding OAR dose constraints.

METHODS

Gross tumour volume (GTV) was contoured on synthetic computerised tomography (sCT) datasets produced using the Velocity adaptive radiotherapy software for eleven patients. The fractions where GTV volume decreased compared to that prior to radiotherapy (reference plan) were considered for personalised progressive dose escalation. The dose to the adapted GTV (GTVAdaptive) was increased until OAR doses were affected (as compared to the original clinical plan). Planning target volume (PTV) coverage was maintained for all plans. Doses were also escalated to the reference plan (GTVClinical) using the same method. Adapted, dose-escalated, plans were combined to estimate accumulated dose, D99 (dose to 99%) of GTVAdapted, PTV D99 and OAR doses and compared with those in the original clinical plans. Knowledge-based planning (KBP) model was developed to predict D99 of the adapted GTV with OAR doses and PTV coverage kept similar to the original clinical plans; prediction accuracy and model verification were performed using further data sets.

RESULTS

Compared to the original clinical plan, dose to GTV was significantly increased without exceeding OAR doses. Adaptive dose-escalation increased the average D99 to GTVAdaptive by 15.1Gy and 8.7Gy compared to the clinical plans. The KBP models were verified and demonstrated prediction accuracy of 0.4% and 0.7% respectively.

CONCLUSION

Progressive adaptive dose escalation can significantly increase the dose to GTV without increasing OAR doses or compromising dose to microscopic disease. This may increase overall survival without increasing toxicities.

Contribution of Neuropilin-1 in Radiation-Survived Subclones of NSCLC Cell Line H1299

Non-small cell lung cancer (NSCLC) is an aggressive lung cancer accounting for approximately 85% of all lung cancer patients. For the patients with Stages IIIA, IIIB, and IIIC, the 5-year survival is low though with the combination with radiotherapy and chemotherapy. In addition, the occurrence of tumor cells (repopulated tumors) that survive irradiation remains a challenge. In our previous report, we subcloned the radiation-surviving tumor cells (IR cells) using the human NSCLC cell line, H1299, and found that the expression of neuropilin-1 (NRP-1) was upregulated in IR cells by the microarray analysis. Here, we investigated the contribution of neuropilin-1 to changes in the characteristics of IR cells. Although there were no differences in angiogenic activity in the tube formation assay between parental and IR cells, the cell motility was increased in IR cells compared to parental cells in the cell migration assay. This enhanced cell motility was suppressed by pretreatment with anti-NRP-1 antibody. Although further studies are necessary to identify other molecules associated with NRP-1, the increase in cellular motility in IR cells might be due to the contribution of NRP-1. Inhibition of NRP-1 would help control tumor malignancy in radiation-surviving NSCLC.

Properties and gene expression profiling of acquired radioresistance in mouse breast cancer cells

Background

Acquired radioresistant cells exhibit many characteristic changes which may influence cancer progression and further treatment options. The purpose of this study is to investigate the changes of radioresistant human epidermal growth factor receptor 2 (HER2)-positive breast cancer cells on both phenotypic and molecular levels.

Methods

We established an acquired radioresistant cell line from its parental NF639 cell line (HER2-positive) by fractionated radiation and assessed changes in cellular morphology, proliferation, migration, anti-apoptosis activity, basal reactive oxygen species (ROS) level and energy metabolism. RNA-sequencing (RNA-seq) was also used to reveal the potential regulating genes and molecular mechanisms associated with the acquired changed phenotypes. Real-time PCR was used to validate the results of RNA-seq.

Results

The NF639R cells exhibited increased radioresistance and enhanced activity of proliferation, migration and anti-apoptosis, but decreased basal ROS. Two main energy metabolism pathways, mitochondrial respiration and glycolytic, were also upregulated. Furthermore, 490 differentially expressed genes were identified by RNA-seq. Enrichment analysis based on Gene Ontology and Kyoto Encyclopedia of Genes and Genomes showed many differently expressed genes were significantly enriched in cell morphology, proliferation, migration, anti-apoptosis, antioxidation, tumor stem cells and energy metabolism and the signaling cascades such as the transforming growth factor-β, Wnt, Hedgehog, vascular endothelial growth factor, retinoic acid-inducible gene I (RIG-I)-like receptor, Toll-like receptor and nucleotide oligomerization domain (NOD)-like receptor were significantly altered in NF639R cells.

Conclusions

In clinical radiotherapy, repeat radiotherapy for short-term recurrence of breast cancer may result in enhanced radioresistance and promote malignant progression. Our research provided hints to understand the tumor resistance to radiotherapy de novo and recurrence with a worse prognosis following radiotherapy.

Berberine Inhibits the Apoptosis-Induced Metastasis by Suppressing the iPLA2/LOX-5/LTB4 Pathway in Hepatocellular Carcinoma

Purpose

Hepatocellular carcinoma (HCC) is one of the most malignant cancers around the world. HCC is less sensitive to conventional cytotoxic agents and easily develops into systemic metastases. However, the molecular mechanisms of the metastasis of HCC are poorly understood and need elucidation.

Materials and Methods

Transwell system of the chemotherapy-challenged and unchallenged HepG2 cells was established. Adhesion assay and scratch-wound assay were utilized to analyze the adhesion and migration of HepG2 cells. iPLA2 and LOX-5 expression were analyzed by Western blot. LTB4 level was analyzed by ELISA.

Results

Chemotherapeutics are traditionally regarded as a way of killing tumor cells; on the other hand, we proved that the chemotherapeutics-induced tumor cell apoptosis can also change the tumor microenvironment by activating the LOX pathway and subsequently release inflammatory factors such as LTB4 which can stimulate the adhesion and migration of the small number of surviving cells. Berberine can reverse the adhesion and migration of HepG2 cells by inhibiting the expression of LOX-5 and reducing the LTB4 production in the tumor microenvironment.

Conclusion

Our study sheds light on a novel anti-metastasis strategy that the combination of Berberine and chemotherapy may prevent the chemotherapy-induced metastasis in HCC.

Hypofractionated Proton Therapy with Concurrent Chemotherapy for Locally Advanced Non-Small Cell Lung Cancer: A Phase 1 Trial from the University of Florida and Proton Collaborative Group

PURPOSE

We report the safety data from the first multicenter phase 1 trial investigating the use of hypofractionated proton therapy with concurrent chemotherapy for patients with stage II or III non-small cell lung cancer.

METHODS AND MATERIALS

From 2013 through 2018, patients with newly diagnosed stage II or III non-small cell lung cancer were enrolled in a multicenter phase 1 clinical trial evaluating concurrent chemotherapy with increasing dose-per-fraction proton therapy. This was a stepwise 5 + 2 dose-intensification protocol with the following dose arms: (1) 2.5 GyRBE per fraction to 60 GyRBE; (2) 3.0 GyRBE per fraction to 60 GyRBE; (3) 3.53 GyRBE per fraction to 60.01 GyRBE; and (4) 4.0 GyRBE per fraction to 60 GyRBE. A dose arm was considered tolerable if no radiation therapy-attributable severe adverse event (SAE) occurred within 90 days of treatment among 5 patients enrolled on the arm or if 1 SAE occurred among 7 patients enrolled. Dose constraints to the heart, brachial plexus, and spinal cord were more conservative at higher doses per fraction.

RESULTS

The study closed early because of slow accrual and competing enrollment in NRG 1308 before accrual was met, with no maximum tolerated dose identified. Eighteen patients were treated, including 5 patients on arms 1 and 2, 7 patients on arm 3, and 1 patient on arm 4. Two SAEs occurred among 7 patients treated at 3.53 GyRBE per fraction; however, per outside expert review, both were attributed to chemotherapy and unrelated to radiation therapy.

CONCLUSIONS

Hypofractionated proton therapy delivered at 2.5 to 3.53 GyRBE per fraction to a dose of 60 GyRBE with concurrent chemotherapy has an acceptable toxicity profile. Further exploration of this regimen is warranted on a phase 2 clinical trial.

Timing of thoracic radiotherapy is more important than dose intensification in patients with limited-stage small cell lung cancer: a parallel comparison of two prospective studies

PURPOSE

The optimal radiotherapy dose/fraction for limited-stage small cell lung cancer (SCLC) is undefined. Our objectives were to compare efficacy between hyperfractionated thoracic radiotherapy (TRT; 1.5 Gy 2 times per day [bid] in 30 fractions) and hypofractionated TRT (2.5 Gy once per day [qd] in 22 fractions), and to explore prognostic factors influencing the prognosis, such as the timing of TRT.

METHODS

Patients enrolled in two independent prospective studies were combined and analyzed. The primary endpoint was local/regional control (LRC). The prognosis was analyzed using the Cox proportional hazards regression model.

RESULTS

Ninety-two and 96 patients were treated with hyperfractionated TRT and hypofractionated TRT, respectively. The 1‑ and 2‑year LRC rates of the two arms were 82.1 and 60.7%, and 84.9 and 68.8% (P = 0.27), respectively. The median overall survival (OS) times (months) were 28.3 (95% confidence interval, CI 16.4-40.1) and 22.0 (95% CI 16.4-27.5), while the 1‑year, 3‑year, and 5‑year OS rates were 85.2, 40.8, and 27.1%, and 76.9, 34.3, and 26.8% (P = 0.37), respectively. Using a multivariate Cox regression study, time (days) from the initiation of chemotherapy to TRT (TCT) ≤43 was associated with improved LRC (hazard radio, HR 0.39, 95% CI 0.20-0.76; P = 0.005). Time (days) from the start of chemotherapy to the end of TRT (SER) ≤63 (HR 0.50, 95% CI 0.32-0.80; P = 0.003) and prophylactic cranial irradiation (HR 0.43; 95% CI 0.29-0.63; P = 0.000) were favorably related to OS. Grade 2/3 acute radiation esophagitis was observed in 37.0 and 17.7% of patients in the hyperfractionated and hypofractionated arms, respectively (P = 0.003).

CONCLUSION

Both hyperfractionated and hypofractionated TRT schedules achieved good LRC and OS for patients with limited-stage SCLC in this study. Keeping TCT ≤43 and SER ≤63 resulted in a better prognosis. The incidence of acute esophagitis was significantly higher in the hyperfractionated arm.

Y90 Radioembolization Dosimetry: Concepts for the Interventional Radiologist

Transarterial radioembolization (TARE) with beta particle emitting microspheres via Yttrium-90 decay has become a fundamental component of the contemporary Interventional Oncology practice. TARE continues to advance as a result of increased utilization, clinical study, technological improvements, and evolving applications. To maximize TARE safety and efficacy, a core understanding of dosimetry is essential. The intent of this overview is to provide the reader with a general survey of radiation physics and biology, device differentiation, patient selection, anatomic assessment, activity administration models, and procedural techniques involved with TARE dosimetry.

Effects of thoracic radiotherapy timing and duration on progression-free survival in limited-stage small cell lung cancer

Concurrent chemoradiotherapy (CRT) has been recommended and applied widely as the standard treatment for limited‐stage small cell lung cancer (LS‐SCLC). However, controversies remain regarding the optimal timing and treatment duration of thoracic radiotherapy (TRT), and their effects on patient survival. To evaluate prognostic values of TRT timing and duration on progression‐free survival (PFS) in LS‐SCLC and their dependence on TRT fractionation and clinicopathological characteristics, we retrospectively analyzed 197 LS‐SCLC patients receiving CRT from 2000 to 2016 at Sun Yat‐sen University Cancer Center. Based on the optimal cut‐off values of TRT timing and duration generated by Cutoff Finder, patients were divided into early TRT/late TRT group and short TRT/long TRT group respectively. Univariate and multivariate Cox analysis were performed to assess correlations of TRT timing, duration, fractionation, and clinicopathological characteristics with PFS. Univariate analysis revealed that early‐initiated TRT (P = 2.54 × 10⁻⁴) and short TRT (P = .001) significantly correlated with longer PFS. Their PFS benefits persisted in patients receiving hyperfractionated TRT and etoposide‐cisplatin (EP) chemotherapy, but were less prominent in those receiving once‐daily TRT and non‐EP chemotherapy. Multivariate analysis further identified early initiated TRT (P = .004) and short TRT (P = .017) as independent prognostic factors for longer PFS in LS‐SCLC. Our study confirmed that early‐initiated TRT and short TRT had positive prognostic roles in LS‐SCLC, especially in patients receiving hyperfractionated TRT and etoposide‐cisplatin chemotherapy. TRT fractionation was not an independent prognostic factor in LS‐SCLC.

Continuous hyperfractionated accelerated radiotherapy using modern radiotherapy techniques for nonsmall cell lung cancer patients unsuitable for chemoradiation

INTRODUCTION

The continuous hyperfractionated and accelerated radiotherapy (CHART) regimen of radiotherapy (RT) for nonsmall cell lung cancer is underused outside the UK. We present the first Indian experience of using CHART for patients, who were not suitable for chemotherapy or concurrent chemo-RT.

METHODS

We retrospectively reviewed the data of patients treated using CHART at our institution between January 2014 and December 2015.

RESULTS

Thirty-seven patients were treated using CHART. Planning methods and dosimetry parameters are described. Three-dimensional conformal RT was used for treatment planning and delivery in 23 patients and volumetric modulated arc RT was necessary for 14 patients. Patients in our series had a median age of 70 years (interquartile range 65.50-74.00) and 86.5% had Stage III disease. Median follow-up was short at 13.0 months. Actuarial rates of 1-year progression-free survival, 1-year overall survival (OS), and 2-year OS were 31.9%, 59.5%, and 28.5%, respectively. This treatment was well tolerated with manageable and some reversible acute esophageal toxicity (91.9% CONCLUSION: Our results indicate that CHART is feasible, safe, and well tolerated in Indian patients who are clinically found to be not suitable for either sequential or concurrent chemo- RT.

MicroRNA molecular profiling identifies potential signaling pathways conferring resistance to chemoradiation in locally-advanced rectal adenocarcinoma

Purpose

There has been growing interest in using chemoradiation (CRT) for non-operative management of rectal cancer, and identifying patients who might benefit most from this approach is crucial. This study identified miRNAs (miRs) associated with clinical outcomes and treatment resistance by evaluating both pre- and post-CRT expression profiles.

Methods

Forty patients, 9 with pathologic complete response (pCR) and 31 with pathologic incomplete response (pIR) were included. MicroRNA was extracted from 40 pre-therapy tumor samples and 31 post-chemoradiation surgical samples with pathologic incomplete response (pIR). A generalized linear model was used to identify miRs associated with pCR. A linear mixed effects model was used to identify miRs differentially expressed before and after treatment. miR expression was dichotomized at the mean and clinical outcomes were evaluated using Cox proportional hazard modeling.

Results

Nine miRs were associated with pCR (p<0.05), but none were significant after false discovery rate correction. Among patients with pIR, 68 miRs were differentially expressed between the pre and post-CRT groups (FDR p<0.05). Ingenuity pathway analysis (IPA) demonstrated multiple signaling networks associated with pIR, including p38MAPK, TP53, AKT, IL-6, and RAS. Increased let-7b was correlated with increased distant metastasis (DM), worse relapse-free survival (RFS), and worse overall survival (OS) (p<0.05).

Conclusions

No miRs were significantly correlated with pCR. We identified miRs that were differentially expressed between pre- and post-CRT tumor samples, and these miRs implicated multiple signaling pathways that may confer resistance to CRT. In addition, we identified an association between increased let-7b and worse clinical outcomes (DM, DFS, OS).

Survival Rates Using Individualized Bioselection Treatment Methods in Patients With Advanced Laryngeal Cancer

Importance

Use of chemoradiotherapy for advanced laryngeal cancer led to a major shift in treatment as an alternative to laryngectomy. Despite widespread adoption of chemoradiotherapy, survival rates have not improved and the original premise of matching neoadjuvant chemotherapy tumor response to determine subsequent treatment has not been followed.

Objective

To determine whether improved survival could be achieved by incorporating a single cycle of neoadjuvant chemotherapy to select patients with advanced disease for either laryngectomy or concurrent chemoradiotherapy.

Design, Setting, and Participants

An unselected cohort of 247 patients with laryngeal cancer in an academic institution between 2002 and 2012 was evaluated. Patients with limited disease (stages I and II) underwent endoscopic resection, radiotherapy, or chemoradiotherapy for deeply invasive T2 lesions. For patients with advanced disease (stages III and IV), neoadjuvant chemotherapy, concurrent chemoradiotherapy, or primary surgery was recommended. Overall survival (OS) and disease-specific survival (DSS) were analyzed. Median follow-up was 48 months. The study was conducted from January 1, 2002, to December 31, 2012; data analysis was completed December 1, 2015.

Interventions

Endoscopic resection, radiotherapy, chemoradiotherapy, neoadjuvant chemotherapy, concurrent chemoradiotherapy, and primary surgery.

Main Outcomes and Measures

Overall survival and DSS.

Results

Of the 247 patients, 191 (77.3%) were male; mean (SD) age was 59.6 (10.4) years. Of 94 patients with limited disease, 33 (35.1%) underwent endoscopic resection; 50 (53.2%), radiotherapy alone; and 11 (11.7%), chemoradiotherapy for deeply invasive T2 lesions. Of 153 patients with advanced disease, 71 (46.4%) received neoadjuvant chemotherapy; 50 (32.7%), concurrent chemoradiotherapy; and 32 (20.9%), surgery. Five-year OS and DSS was 75% (95% CI, 68%-81%) and 83% (95% CI, 77%-88%), respectively, for the entire cohort. The DSS was 92% (95% CI, 83%-97%) for patients with stage I or II and 78% (95% CI, 69%-84%) for patients with stage III or IV disease. For patients with advanced disease, 5-year OS and DSS ranged from 78% (95% CI, 55%-90%) and 91% (95% CI, 67%-98%), respectively, for surgery; to 76% (95% CI, 63%-85%) and 79% (95% CI, 67%-88%), respectively, for neoadjuvant bioselection; and to 61% (95% CI, 44%-75%) and 66% (95% CI, 48%-79%), respectively, for primary chemoradiotherapy. Propensity-adjusted, multivariable controlling for known prognostic factors DSS was significantly improved in the neoadjuvant group compared with the chemoradiotherapy group (hazard ratio [HR], 0.48; 95% CI, 0.29-0.80).

Conclusions and Relevance

Superior survival rates were achieved with a bioselective treatment approach using a single cycle of neoadjuvant chemotherapy. Good survival rates were also achieved in patients selected for primary surgery, and both neoadjuvant chemotherapy and primary surgery were better than survival rates with concurrent chemoradiotherapy, suggesting that the optimal individualized treatment approach for patients with advanced laryngeal cancer has not yet been defined.

Radiobiology of stereotactic body radiation therapy (SBRT)

Recent advances in the technology of radiotherapy have enabled the development of new therapeutic modalities that deliver radiation with very high accuracy, reduced margins and high dose conformation, allowing the reduction of healthy tissue irradiated and therefore minimizing the risk of toxicity. The next step was to increase the total tumor dose using conventional fractionation (which remains the best way to relatively radioprotect healthy tissues when large volumes are treated) or to use new fractionation schemes with greater biological effectiveness. Based on the experience gained in radiosurgery, the latter way was chosen for small and well-defined tumors in the body. Stereotactic body radiotherapy delivers high doses of radiation to small and well-defined targets in an extreme hypofractionated (and accelerated) scheme with a very high biological effectiveness obtaining very good initial clinical results in terms of local tumor control and acceptable rate of late complications. In fact, we realize a posteriori that it was not feasible to administer such biologically equivalent dose in a conventional fractionation because the treatment could last several months. So far, these new therapeutic modalities have been developed due to technologic advances in image guidance and treatment delivery but without a solid biological basis. It is the role of traditional radiobiology (and molecular radiobiology) to explain the effects of high doses of ionizing radiation on tumor and normal tissues. Only through a better understanding of how high doses of ionizing radiation act, clinicians will know exactly what we do, allowing us in the future to refine our treatments. This article attempts to describe through simple and understandable concepts the known aspects of the biological action of high doses of radiation on tumor and normal tissues, but it is clear that we need much more basic research to better understand the biology of high doses of radiation.

MicroRNA-124 regulates the radiosensitivity of non-small cell lung cancer cells by targeting TXNRD1

Radiation treatment remains one of the major modalities in the treatment of lung cancer. Although the majority of patients initially respond to treatment with radiation, resistance inevitably develops and leads to treatment failure. Therefore, the identification of the underlying molecular mechanisms of radiation resistance may facilitate the development of novel approaches for overcoming resistance, and enhance the efficacy of treatment with radiation in lung and other types of cancer. In the present study we established three radiation-resistant sub-cell lines derived from the radiation-sensitive lung cancer cell line HCC827. Using a polymerase chain reaction microRNA (miRNA) array, multiple miRNAs were identified to be markedly downregulated in radiation-resistant cells, including miRNA (miR)-124, miR-191 and miR-205. It was observed that overexpression of miR-124 sensitized the resistant cells to treatment with radiation and that thioredoxin reductase 1 (TXNRD1) is a novel target of miR-124. Furthermore, it was demonstrated that knockdown of TXNRD1 using small interfering RNA increased the basal level of reactive oxygen species and sensitized the cells to radiation treatment. The results of the present study demonstrated that multiple miRNAs are downregulated in radiation-resistant lung cancer cells and that downregulation of miR-124 mediates radiation resistance through the targeting of TXNRD1 mRNA expression. The present study revealed a novel molecular mechanism of miRNA-mediated radiation resistance and identified miR-124-regulated TXNRD1 as a novel therapeutic target for overcoming radiation resistance in the treatment of lung cancer.

Stereotactic Body Radiation Therapy Boost After Concurrent Chemoradiation for Locally Advanced Non-Small Cell Lung Cancer: A Phase 1 Dose Escalation Study

PURPOSE

Stereotactic body radiation therapy (SBRT) boost to primary and nodal disease after chemoradiation has potential to improve outcomes for advanced non-small cell lung cancer (NSCLC). A dose escalation study was initiated to evaluate the maximum tolerated dose (MTD).

METHODS AND MATERIALS

Eligible patients received chemoradiation to a dose of 50.4 Gy in 28 fractions and had primary and nodal volumes appropriate for SBRT boost (<120 cc and <60 cc, respectively). SBRT was delivered in 2 fractions after chemoradiation. Dose was escalated from 16 to 28 Gy in 2 Gy/fraction increments, resulting in 4 dose cohorts. MTD was defined when ≥2 of 6 patients per cohort experienced any treatment-related grade 3 to 5 toxicity within 4 weeks of treatment or the maximum dose was reached. Late toxicity, disease control, and survival were also evaluated.

RESULTS

Twelve patients (3 per dose level) underwent treatment. All treatment plans met predetermined dose-volume constraints. The mean age was 64 years. Most patients had stage III disease (92%) and were medically inoperable (92%). The maximum dose level was reached with no grade 3 to 5 acute toxicities. At a median follow-up time of 16 months, 1-year local-regional control (LRC) was 78%. LRC was 50% at <24 Gy and 100% at ≥24 Gy (P=.02). Overall survival at 1 year was 67%. Late toxicity (grade 3-5) was seen in only 1 patient who experienced fatal bronchopulmonary hemorrhage (grade 5). There were no predetermined dose constraints for the proximal bronchial-vascular tree (PBV) in this study. This patient's 4-cc PBV dose was substantially higher than that received by other patients in all 4 cohorts and was associated with the toxicity observed: 20.3 Gy (P<.05) and 73.5 Gy (P=.07) for SBRT boost and total treatment, respectively.

CONCLUSIONS

SBRT boost to both primary and nodal disease after chemoradiation is feasible and well tolerated. Local control rates are encouraging, especially at doses ≥24 Gy in 2 fractions. Toxicity at the PBV is a concern but potentially can be avoided with strict dose-volume constraints.

Emergent properties of a computational model of tumour growth

While there have been enormous advances in our understanding of the genetic drivers and molecular pathways involved in cancer in recent decades, there also remain key areas of dispute with respect to fundamental theories of cancer. The accumulation of vast new datasets from genomics and other fields, in addition to detailed descriptions of molecular pathways, cloud the issues and lead to ever greater complexity. One strategy in dealing with such complexity is to develop models to replicate salient features of the system and therefore to generate hypotheses which reflect on the real system. A simple tumour growth model is outlined which displays emergent behaviours that correspond to a number of clinically relevant phenomena including tumour growth, intra-tumour heterogeneity, growth arrest and accelerated repopulation following cytotoxic insult. Analysis of model data suggests that the processes of cell competition and apoptosis are key drivers of these emergent behaviours. Questions are raised as to the role of cell competition and cell death in physical cancer growth and the relevance that these have to cancer research in general is discussed.

Radiosensitization in esophageal squamous cell carcinoma: Effect of polo-like kinase 1 inhibition

PURPOSE

This study examined the efficacy of polo-like kinase 1 (PLK1) inhibition on radiosensitivity in vitro and in vivo by a pharmacologic approach using the highly potent PLK1 inhibitor volasertib.

METHODS AND MATERIALS

Human esophageal squamous cell carcinoma (ESCC) cell lines KYSE 70 and KYSE 150 were used to evaluate the synergistic effect of volasertib and irradiation in vitro using cell viability assay, colony formation assay, cell cycle phase analysis, and western blot, and in vivo using ectopic tumor models.

RESULTS

Volasertib decreased ESCC cell proliferation in a dose- and time-dependent manner. Combination of volasertib and radiation caused G2/M cell cycle arrest, increased cyclin B levels, and induced apoptosis. Volasertib significantly enhanced radiation-induced death in ESCC cells by a mechanism involving the enhancement of histone H3 phosphorylation and significant cell cycle interruption. The combination of volasertib plus irradiation delayed the growth of ESCC tumor xenografts markedly compared with either treatment modality alone.

CONCLUSIONS

The in vitro results suggested that targeting PLK1 might be a viable approach to improve the effects of radiation in ESCC. In vivo studies showed that PLK1 inhibition with volasertib during irradiation significantly improved local tumor control when compared to irradiation or drug treatment alone.