Very high-energy electron therapy as light-particle alternative to transmission proton FLASH therapy - An evaluation of dosimetric performances

PURPOSE

Clinical translation of FLASH-radiotherapy (RT) to deep-seated tumours is still a technological challenge. One proposed solution consists of using ultra-high dose rate transmission proton (TP) beams of about 200-250 MeV to irradiate the tumour with the flat entrance of the proton depth-dose profile. This work evaluates the dosimetric performance of very high-energy electron (VHEE)-based RT (50-250 MeV) as a potential alternative to TP-based RT for the clinical transfer of the FLASH effect.

METHODS

Basic physics characteristics of VHEE and TP beams were compared utilizing Monte Carlo simulations in water. A VHEE-enabled research treatment planning system was used to evaluate the plan quality achievable with VHEE beams of different energies, compared to 250 MeV TP beams for a glioblastoma, an oesophagus, and a prostate cancer case.

RESULTS

Like TP, VHEE above 100 MeV can treat targets with roughly flat (within ± 20 %) depth-dose distributions. The achievable dosimetric target conformity and adjacent organs-at-risk (OAR) sparing is consequently driven for both modalities by their lateral beam penumbrae. Electron beams of 400[500] MeV match the penumbra of 200[250] MeV TP beams and penumbra is increased for lower electron energies. For the investigated patient cases, VHEE plans with energies of 150 MeV and above achieved a dosimetric plan quality comparable to that of 250 MeV TP plans. For the glioblastoma and the oesophagus case, although having a decreased conformity, even 100 MeV VHEE plans provided a similar target coverage and OAR sparing compared to TP.

CONCLUSIONS

VHEE-based FLASH-RT using sufficiently high beam energies may provide a lighter-particle alternative to TP-based FLASH-RT with comparable dosimetric plan quality.

Effect of Conventional and Ultrahigh Dose Rate FLASH Irradiations on Preclinical Tumor Models: A Systematic Analysis

PURPOSE

Compared with conventional dose rate irradiation (CONV), ultrahigh dose rate irradiation (UHDR) has shown superior normal tissue sparing. However, a clinically relevant widening of the therapeutic window by UHDR, termed "FLASH effect," also depends on the tumor toxicity obtained by UHDR. Based on a combined analysis of published literature, the current study examined the hypothesis of tumor isoefficacy for UHDR versus CONV and aimed to identify potential knowledge gaps to inspire future in vivo studies.

METHODS AND MATERIALS

A systematic literature search identified publications assessing in vivo tumor responses comparing UHDR and CONV. Qualitative and quantitative analyses were performed, including combined analyses of tumor growth and survival data.

RESULTS

We identified 66 data sets from 15 publications that compared UHDR and CONV for tumor efficacy. The median number of animals per group was 9 (range 3-15) and the median follow-up period was 30.5 days (range 11-230) after the first irradiation. Tumor growth assays were the predominant model used. Combined statistical analyses of tumor growth and survival data are consistent with UHDR isoefficacy compared with CONV. Only 1 study determined tumor-controlling dose (TCD50) and reported statistically nonsignificant differences.

CONCLUSIONS

The combined quantitative analyses of tumor responses support the assumption of UHDR isoefficacy compared with CONV. However, the comparisons are primarily based on heterogeneous tumor growth assays with limited numbers of animals and short follow-up, and most studies do not assess long-term tumor control probability. Therefore, the assays may be insensitive in resolving smaller response differences, such as responses of radioresistant tumor subclones. Hence, tumor cure experiments, including additional TCD50 experiments, are needed to confirm the assumption of isoeffectiveness in curative settings.

Updates on radiotherapy-immunotherapy combinations: Proceedings of 6th annual ImmunoRad conference

Focal radiation therapy (RT) has attracted considerable attention as a combinatorial partner for immunotherapy (IT), largely reflecting a well-defined, predictable safety profile and at least some potential for immunostimulation. However, only a few RT-IT combinations have been tested successfully in patients with cancer, highlighting the urgent need for an improved understanding of the interaction between RT and IT in both preclinical and clinical scenarios. Every year since 2016, ImmunoRad gathers experts working at the interface between RT and IT to provide a forum for education and discussion, with the ultimate goal of fostering progress in the field at both preclinical and clinical levels. Here, we summarize the key concepts and findings presented at the Sixth Annual ImmunoRad conference.

Opportunities and challenges of low-dose radiation to enable immunotherapy efficacy

Therapeutic monoclonal antibodies blocking different immune checkpoints, have demonstrated efficacy against a wide variety of solid tumors. The exclusion or absence of lymphocytes within the tumor microenvironment (TME) is one of the main resistance mechanisms to immune checkpoint inhibitor (ICI)-based therapies. Therefore, there is a growing interest in identifying novel approaches to promote T cell infiltration on immune-deserted (cold) and immune-excluded tumors to turn them into inflamed (hot) tumors. Here, we provide a comprehensive overview of the recently published studies showing the potential of low-dose radiation (LDRT) to reprogram the TME to allow and promote T-cell infiltration and thus, improve currently approved ICI-based therapies.

Independent Reproduction of the FLASH Effect on the Gastrointestinal Tract: A Multi-Institutional Comparative Study

FLASH radiation therapy (RT) is a promising new paradigm in radiation oncology. However, a major question that remains is the robustness and reproducibility of the FLASH effect when different irradiators are used on animals or patients with different genetic backgrounds, diets, and microbiomes, all of which can influence the effects of radiation on normal tissues. To address questions of rigor and reproducibility across different centers, we analyzed independent data sets from The University of Texas MD Anderson Cancer Center and from Lausanne University (CHUV). Both centers investigated acute effects after total abdominal irradiation to C57BL/6 animals delivered by the FLASH Mobetron system. The two centers used similar beam parameters but otherwise conducted the studies independently. The FLASH-enabled animal survival and intestinal crypt regeneration after irradiation were comparable between the two centers. These findings, together with previously published data using a converted linear accelerator, show that a robust and reproducible FLASH effect can be induced as long as the same set of irradiation parameters are used.

Outcomes and endpoints of relevance in gynecologic cancer clinical trials

Drug development is paramount to improve outcomes in patients with gynecologic cancers. A randomized clinical trial should measure whether a clinically relevant improvement is detected with the new intervention compared with the standard of care, using reproductible and appropriate endpoints. Clinically meaningful improvements in overall survival and/or quality of life (QoL) are the gold standards to measure benefit of new therapeutic strategies. Alternative endpoints, such as progression-free survival, provide an earlier measure of the effect of the new therapeutic drug, and are not confounded by the effect of subsequent lines of therapy. Yet, its surrogacy with improved overall survival or QoL is unclear in gynecologic malignancies. Of relevance to studies assessing maintenance strategies are other time-to-event endpoints, such as progression-free survival two and time to second subsequent treatment, which provide valuable information on the disease control in the longer term. Translational and biomarker studies are increasingly being incorporated into gynecologic oncology clinical trials, as they may allow understanding of the biology of the disease, resistance mechanisms, and enable a better selection of patients who might benefit from the new therapeutic strategy. Globally, the endpoint selection of a clinical trial will differ according to the type of study, population, disease setting, and type of therapeutic strategy. This review provides an overview of primary and secondary endpoint selection of relevance for gynecologic oncology clinical trials.

Toxicity, quality of life, and PSA control after 50 Gy stereotactic body radiation therapy to the dominant intraprostatic nodule with the use of a rectal spacer: results of a phase I/II study

OBJECTIVES

We conducted a phase I/II prospective trial to determine whether stereotactic dose escalation to the dominant intra-prostatic nodule (DIN) up to 50 Gy incorporating a rectal balloon spacer is safe, does not affect patient quality of life, and preserves local control in patients with intermediate-high risk PCa.

METHODS

Eligible patients included males with stage ≤T3b localized disease, a prostate-specific antigen (PSA) level ≤50 , International Prostate Symptom Score (IPSS) ≤14, and a gland volume ≤70 cm³. Patients underwent perirectal spacer placement, followed by a planning MRI and were subsequently treated with SBRT doses of 36.25 Gy in five fractions to the whole prostate while simultaneously escalating doses to the magnetic resonance image visible DIN up to 50 Gy. Primary endpoint: safety. Secondary endpoints: biochemical control, quality of life (QofL), and dosimetry outcome.

RESULTS

Nine patients were treated in the Phase I part of the study. Dose limiting toxicities (DLTs) were not observed. Further characterization of tolerability and efficacy was conducted in the subsequent 24 patients irradiated at the recommended Phase II dose (50 Gy, RP2D). At a median follow-up of 61 months, biochemical control is 69%. Grade 1 and 2 acute GU and GI toxicity was 57.5 and 15%, and 24.2 and 6.1%, respectively. Grade 1 and 2 late GU and GI toxicity was 66.6 and 12.1%, and 15.1 and 3%, respectively. No Grade 3 or higher toxicity was reported. QofL data confirmed physician's reported side effects. Dosimetry analysis showed adherence to the doses prescribed in the protocol.

CONCLUSIONS

SBRT of the whole prostate with 36.25 Gy in 5 fractions and dose escalation to 50 Gy to the DIN, when combined with a peri-rectal balloon spacer, was tolerable and established the RP2D. QofL analysis showed minimal negative impact in GU, GI, and sexual domains.

ADVANCES IN KNOWLEDGE

Extreme hypofractionated prostate radiation therapy with focal dose escalation to the DIN is well tolerated with efficacy comparable to normal fractionated radiation therapy.

Low-dose irradiation for reversing immunotherapy resistance: how to translate?

The use of low-dose irradiation (LDI) for mobilizing innate and adaptive immunity is gaining interest among the scientific community. Recent evidence suggests that LDI can reprogramme the tumor microenvironment, induce inflammation and turn cold tumors susceptible to immunecheckpoint blockade therapy. Translating immuno-radiation preclinical findings in the clinic is more challenging than expected. We propose therapeutic strategies for combining LDI with immunotherapy, and emphasize the importance of pursuing clinical research to determine optimal radiation dosage, fractionation, volumes, and sequencing to stimulate immune-mediated tumor responses.

Overcoming Immune Resistance With Radiation Therapy in Prostate Cancer

Prostate cancer is the second most common cancer in men and represents a significant healthcare burden worldwide. Therapeutic options in the metastatic castration-resistant setting remain limited, despite advances in androgen deprivation therapy, precision medicine and targeted therapies. In this review, we summarize the role of immunotherapy in prostate cancer and offer perspectives on opportunities for future development, based on current knowledge of the immunosuppressive tumor microenvironment. Furthermore, we discuss the potential for synergistic therapeutic strategies with modern radiotherapy, through modulation of the tumor microenvironment. Emerging clinical and pre-clinical data suggest that radiation can convert immune desert tumors into an inflamed immunological hub, potentially sensitive to immunotherapy.

Stereotactic Body Radiation Therapy in Patients with Oligometastatic Disease: Clinical State of the Art and Perspectives

Stereotactic body radiation therapy (SBRT) is a form of radiation therapy (RT) in which a small number of high doses of radiation are delivered to a target volume using highly sophisticated equipment. Stereotactic body radiation therapy is crucial in two cancer stages: early primary cancer and oligometastatic disease, with the goal of inducing complete cancer remission in both. This treatment method is commonly used to treat a variety of disease types. Over the years, a growing body of clinical evidence on the use of SBRT for the treatment of primary and metastatic tumors has accumulated, with efficacy and safety demonstrated in randomized clinical trials. This article will review the technical and clinical aspects of SBRT according to disease type and clinical indication.

SMARCA4-Deficient Carcinoma of Uterine Cervix Resembling SCCOHT-Case Report

Small cell carcinoma of hypercalcemic type (SCCOHT) is a rare gynaecological neoplasm, originating mostly in the ovaries. Cervical origin of this very aggressive malignancy with unknown histogenesis is an extremely rare condition, without published management recommendations. Alterations in SMARCA4 gene are supposed to play the major role in SCCOHT oncogenesis and their identification is crucial for the diagnosis. Adequate genetic counselling of the patients and their families seems to be of great importance. Optimal management and treatment approaches are not known yet but may extremely influence the prognosis of young female patients that suffer from this very resistant disease. Nowadays, a translational research seems to be the key for the further diagnostic and treatment strategies of SCCOHT. The purpose of the case report is to provide practical information and useful recommendations on the diagnosis, management, and treatment of SMARCA4-deficient carcinoma of the uterine cervix resembling SCCOHT.

Low-Dose Radiotherapy Reverses Tumor Immune Desertification and Resistance to Immunotherapy

Developing strategies to inflame tumors is critical for increasing response to immunotherapy. Here, we report that low-dose radiotherapy (LDRT) of murine tumors promotes T-cell infiltration and enables responsiveness to combinatorial immunotherapy in an IFN-dependent manner. Treatment efficacy relied upon mobilizing both adaptive and innate immunity and depended on both cytotoxic CD4⁺ and CD8⁺ T cells. LDRT elicited predominantly CD4⁺ cells with features of exhausted effector cytotoxic cells, with a subset expressing NKG2D and exhibiting proliferative capacity, as well as a unique subset of activated dendritic cells expressing the NKG2D ligand RAE1. We translated these findings to a phase I clinical trial administering LDRT, low-dose cyclophosphamide, and immune checkpoint blockade to patients with immune-desert tumors. In responsive patients, the combinatorial treatment triggered T-cell infiltration, predominantly of CD4⁺ cells with Th1 signatures. Our data support the rational combination of LDRT with immunotherapy for effectively treating low T cell-infiltrated tumors. SIGNIFICANCE: Low-dose radiation reprogrammed the tumor microenvironment of tumors with scarce immune infiltration and together with immunotherapy induced simultaneous mobilization of innate and adaptive immunity, predominantly CD4⁺ effector T cells, to achieve tumor control dependent on NKG2D. The combination induced important responses in patients with metastatic immune-cold tumors.This article is highlighted in the In This Issue feature, p. 1.

So-Called Serous Carcinoma of the Uterine Cervix with Mutation: Case Report and Review of the Literature

Serous carcinoma of the uterine cervix (SCUC) is now believed to be a morphological variant of an HPV-associated endocervical adenocarcinoma or a metastasis from a serous carcinoma of the upper tract. In terms of mutational status as detected by next-generation sequencing (NGS), this controversial entity has not been characterized yet. We describe the case of a patient with a carcinoma categorized as stage IVB SCUC, initially treated with carboplatin, paclitaxel, and bevacizumab, followed by maintenance with bevacizumab. After locoregional progression, radiotherapy was administered. Unfortunately, further progression was observed, and carboplatin was resumed. Considering the presence of a BRCA2 mutation as detected by NGS, treatment with a PARP inhibitor (olaparib) was decided and allowed disease control for 6 months. We believe that BRCA mutation may be systematically searched in patients suffering from carcinomas formerly referred to as SCUC and that targeted treatments should be considered.

Short Androgen Suppression and Radiation Dose Escalation in Prostate Cancer: 12-Year Results of EORTC Trial 22991 in Patients With Localized Intermediate-Risk Disease

PURPOSE

The European Organisation for Research and Treatment of Cancer (EORTC) trial 22991 (NCT00021450) showed that 6 months of concomitant and adjuvant androgen suppression (AS) improves event- (EFS, Phoenix) and clinical disease-free survival (DFS) of intermediate- and high-risk localized prostatic carcinoma, treated by external-beam radiotherapy (EBRT) at 70-78 Gy. We report the long-term results in intermediate-risk patients treated with 74 or 78 Gy EBRT, as per current guidelines.

PATIENT AND METHODS

Of 819 patients randomly assigned between EBRT or EBRT plus AS started on day 1 of EBRT, 481 entered with intermediate risk (International Union Against Cancer TNM 1997 cT1b-c or T2a with prostate-specific antigen (PSA) ≥ 10 ng/mL or Gleason ≤ 7 and PSA ≤ 20 ng/mL, N0M0) and had EBRT planned at 74 (342 patients, 71.1%) or 78 Gy (139 patients, 28.9%). We report the trial primary end point EFS, DFS, distant metastasis-free survival (DMFS), and overall survival (OS) by intention-to-treat stratified by EBRT dose at two-sided α = 5%.

RESULTS

At a median follow-up of 12.2 years, 92 of 245 patients and 132 of 236 had EFS events in the EBRT plus AS and EBRT arm, respectively, mostly PSA relapse (48.7%) or death (45.1%). EBRT plus AS improved EFS and DFS (hazard ratio [HR] = 0.53; CI, 0.41 to 0.70; P < .001 and HR = 0.67; CI, 0.49 to 0.90; P = .008). At 10 years, DMFS was 79.3% (CI, 73.4 to 84.0) with EBRT plus AS and 72.7% (CI, 66.2 to 78.2) with EBRT (HR = 0.74; CI, 0.53 to 1.02; P = .065). With 140 deaths (EBRT plus AS: 64; EBRT: 76), 10-year OS was 80.0% (CI, 74.1 to 84.7) with EBRT plus AS and 74.3% (CI, 67.8 to 79.7) with EBRT, but not statistically significantly different (HR = 0.74; CI, 0.53 to 1.04; P = .082).

CONCLUSION

Six months of concomitant and adjuvant AS statistically significantly improves EFS and DFS in intermediate-risk prostatic carcinoma, treated by irradiation at 74 or 78 Gy. The effects on OS and DMFS did not reach statistical significance.

A new method to visualize and to spare the ureters during SBRT for oligo metastatic patients

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Ureteral injury following abdominal irradiation may have serious consequences.

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Urography CT scan is a simple procedure to spare ureters during SBRT.

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Using a urography CT scan can significantly reduce the dose to the ureters.

This article describes a ureter-sparing procedure used to treat lymph node metastases with SBRT. We delivered 35 Gy in 5 fractions of 7 Gy to patients with lesions located less than 7 mm from the ureters using a urography CT scan for planification. Two dosimetry plans were created, one using a CT scan urography-based contour and the other using the native phase. PTV coverage were not statistically different but this technique was able to significantly reduce median delivered Dmax to the ureters. These preliminary results demonstrate the feasibility of locating the ureters in a planning CT scan to protect them.

VEGFR Inhibitors for Uterine Metastatic Perivascular Epithelioid Tumors (PEComa) Resistant to mTOR Inhibitors. A Case Report and Review of Literature

Uterine perivascular epithelioid cell tumors (PEComas) are rare neoplasms. PI3K/AKT/mTOR pathway upregulation is critical for their pathogenesis and is often associated with TSC1/TSC2 inactivation. Although first line mTOR inhibitors are an effective treatment, metastatic PEComas eventually progress. A 53-year-old woman presented a 4-month history of post-menopausal vaginal bleeding. Clinical and radiological examination detected a uterine mass and a single S1 bone lesion. The patient underwent a radical hysterectomy and bone biopsy. The anatomopathological evaluation concluded to an oligo-metastatic uterine PEComa. The tumor harbored a heterozygous deletion of 9q34 that contains the TSC1 gene. Concerning the primary lesion, the resection was complete and the single bone metastasis was treated with radiotherapy. Three months later, the patient presented bone, lung and subcutaneous metastatic progression. An everolimus and denosumab treatment was initiated. After 2 years of treatment, a clinically significant bone, lung and subcutaneous progression was detected. Following a literature review of the possible therapeutic options, we initiated a second line treatment by pazopanib. This treatment resulted in regression of the subcutaneous lesions and stability of lung and bone metastases. In this challenging, rare setting, our report suggests single agent, anti-angiogenic, tyrosine kinase inhibitor to be effective as second line treatment of metastatic uterine PEComa progressing on mTOR inhibitors.

Abscopal effect in a patient with malignant pleural mesothelioma treated with palliative radiotherapy and pembrolizumab

The abscopal effect describes the ability of locally administered radiotherapy to induce systemic antitumor effects. Although mentioned for the first time in the 1950s, records of abscopal effects, considered to be immune-mediated, are scarce with radiotherapy alone. However, with the continued development and use of immunotherapy, reports on the abscopal effect have become increasingly frequent during the last decade. Here, we report a patient with advanced malignant pleural mesothelioma who had progressive disease while on the anti-PDL1 inhibitor pembrolizumab and showed an abscopal response after palliative radiotherapy.

High versus low dose irradiation for tumor immune reprogramming

Local administration of ionizing radiation to tumors can promote anticancer immune responses that lead to the abscopal regression of distant metastases, especially in patients receiving systemic immune-checkpoint inhibitors. Growing preclinical evidence indicates that high-dose irradiation administered locally to destroy malignant lesions, can promote the release of danger-associated molecular patterns that lead to the recruitment of immune cells, thus inducing a systemic response against tumor antigens that protects against local disease relapse and also mediates distant antineoplastic effects. An accumulating body of preclinical evidence supports also the implementation of low-dose irradiation to induce tumor immune reprogramming. Here, we provide the rationale for a clinical research agenda to refine future clinical practice based on innovative combinations of radiation-immunotherapy.

Efficacy of chemotherapy and atezolizumab in patients with non-small-cell lung cancer receiving antibiotics and proton pump inhibitors: pooled post hoc analyses of the OAK and POPLAR trials

BACKGROUND

Preclinical data have shown that proton pump inhibitors (PPI) can modulate the microbiome, and single-arm studies suggested that antibiotics (ATB) may decrease the efficacy of immune checkpoint inhibitors (ICI), but randomized controlled trial data are lacking. This pooled analysis evaluated the effect of ATB and PPI on outcome in patients randomized between ICI and chemotherapy.

PATIENTS AND METHODS

This retrospective analysis used pooled data from the phase II POPLAR (NCT01903993) and phase III OAK (NCT02008227) trials, which included 1512 patients with previously treated non-small-cell lung cancer (NSCLC) randomly assigned to receive atezolizumab (n = 757) or docetaxel (n = 755). The main objective of this analysis was to assess the impact of ATB and PPI use on overall survival (OS) and progression-free survival (PFS).

RESULTS

A total of 169 (22.3%) patients in the atezolizumab group and 202 (26.8%) in the docetaxel group received ATB, and 234 (30.9%) and 260 (34.4%), respectively, received PPI. Multivariate analysis in all patients revealed that ATB were associated with shorter OS [hazard ratio (HR) 1.20, 95% confidence interval (CI) 1.04-1.39], as was PPI (HR 1.26, 95% CI 1.10-1.44). Within the atezolizumab population, OS was significantly shorter in patients who received ATB (8.5 versus 14.1 months, HR 1.32, 95% CI 1.06-1.63, P = 0.01) or PPI (9.6 versus 14.5 months, HR 1.45, 95% CI 1.20-1.75, P = 0.0001). PPI use was associated with shorter PFS in the atezolizumab population (1.9 versus 2.8 months, HR 1.30, 95% CI 1.10-1.53, P = 0.001). There was no association between ATB and PPI use and PFS or OS within the docetaxel population.

CONCLUSION

In this unplanned analysis from two randomized trials, data suggest that ATB or PPI use in patients with metastatic NSCLC is associated with poor outcome and may influence the efficacy of ICI.

50-Gy Stereotactic Body Radiation Therapy to the Dominant Intraprostatic Nodule: Results From a Phase 1a/b Trial

PURPOSE

Although localized prostate cancer (PCa) is multifocal, the dominant intraprostatic nodule (DIN) is responsible for disease progression after radiation therapy. PCa expresses antigens that could be recognized by the immune system. We therefore hypothesized that stereotactic dose escalation to the DIN is safe, may increase local control, and may initiate tumor-specific immune responses.

PATIENTS AND METHODS

Patients with localized PCa were treated with stereotactic extreme hypofractionated doses of 36.25 Gy in 5 fractions to the whole prostate while simultaneously escalating doses to the magnetic resonance image-visible DIN (45 Gy, 47.5 Gy, and 50 Gy in 5 fractions). The phase 1a part was designed to determine the recommended phase 1b dose in a "3 + 3" cohort-based, dose-escalation design. The primary endpoint was dose-limiting toxicities defined as ≥grade 3 gastrointestinal (GI) or genitourinary (GU) toxicity (or both) by National Cancer Institute Common Terminology Criteria for Adverse Events (version 4) up to 90 days after the first radiation fraction. The secondary endpoints were prostate-specific antigen kinetics, quality of life (QoL), and blood immunologic responses.

RESULTS

Nine patients were treated in phase 1a. No dose-limiting toxicities were observed at either level, and therefore the maximum tolerated dose was not reached. Further characterization of tolerability, efficacy, and immunologic outcomes was conducted in the subsequent 11 patients irradiated at the highest dose level (50 Gy) in the phase 1b expansion cohort. Toxicity was 45% and 25% for grades 1 and 2 GU, and 20% and 5% for grades 1 and 2 GI, respectively. No grade 3 or worse toxicity was reported. The average (±standard error of the mean) of the QoL assessments at baseline and at 3-month posttreatment were 0.8 (±0.8) and 3.5 (±1.5) for the bowel (mean difference, 2.7; 95% confidence interval, 0.1-5), and 6.4 (±0.8) and 7.27 (±0.9) for the International Prostate Symptom Score (mean difference, 0.87; 95% confidence interval, 0.3-1.9), respectively. A subset of patients developed antigen-specific immune responses against prostate-specific membrane antigen (n = 2), prostatic acid phosphatase (n = 1), prostate stem cell antigen (n = 4), and prostate-specific antigen (n = 2).

CONCLUSIONS

Irradiation of the whole prostate with 36.25 Gy in 5 fractions and dose escalation to 50 Gy to the DIN was tolerable and determined as the recommended phase 1b dose. This treatment has promising antitumor activity, which will be confirmed by the ongoing phase 2 part. Preliminary QoL analysis showed minimal impact in GU, GI, and sexual domains. Stereotactic irradiation induced antigen-specific immune responses in a subset of patients.

(18F)-FDG PET/CT parameters to predict survival and recurrence in patients with locally advanced cervical cancer treated with chemoradiotherapy

PURPOSE

To identify predictive (¹⁸F)-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT)-based parameters for locoregional control, disease-free survival and overall survival, by testing different thresholds of metabolic tumor volume and total lesion glycolysis in patients with locally-advanced cervical cancer.

PATIENTS AND METHODS

Thirty-seven patients treated with standard chemoirradiation underwent a pretreatment (¹⁸F)-FDG-PET/CT. Using different thresholds of maximum standardized uptake value, the following PET parameters were computed: maximum standardized uptake value, mean standardized uptake value, metabolic tumor volume and total lesion glycolysis for primary tumor and lymph nodes and a new parameter combining the metabolic tumor volume and the distance between lymph nodes and the primary tumor, namely metabolic node distance. Correlation between PET and clinical parameters with clinical outcome (overall survival, disease-free survival, and locoregional control) was assessed using univariate and multivariate analyses (Cox model).

RESULTS

In univariate analyses, PET/CT parameters associated with overall survival and disease-free survival were: metabolic tumor volume and total lesion glycolysis of the primary tumor, total lesion glycolysis of lymph nodes and metabolic node distance. The most predictive threshold segmentation for metabolic tumor volume and total lesion glycolysis was 48% of maximum standardized uptake value for the primary tumor and 30% for the lymph nodes. In multivariate Cox analysis, the total lesion glycolysis of primary tumor 48% and metabolic node distance were the two independent risk factors for overall survival (P<0.01), disease-free survival (P<0.01) and locoregional control (P=0.046).

CONCLUSION

Total lesion glycolysis of primary tumor and distance between the invaded positive lymph node and the primary tumor seem to have the highest predictive value when compared to classical clinical prognostic parameters and may be useful to identify high risk groups at time of diagnosis and to tailor the therapeutic approach in locally-advanced cervical cancer.

Prostate irradiation with focal dose escalation to the intraprostatic dominant nodule: a systematic review

Radiation therapy (RT) is a curative treatment option for localized prostate cancer. Prostate irradiation with focal dose escalation to the intraprostatic dominant nodule (IDN) is an emerging treatment option that involves the prophylactic irradiation of the whole prostate while increasing RT doses to the visible prostatic tumor. Because of the lack of large multicentre trials, a systematic review was performed in an attempt to get an overview on the feasibility and efficacy of focal dose escalation to the IDN.

A bibliographic search for articles in English, which were listed in MEDLINE from 2000 to 2016 to identify publications on RT with focal directed boost to the IDN, was performed. The review was completed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.

Twenty-two articles describing 1,378 patients treated with RT using focal boost were identified and fulfilled the selection criteria. Intensity-modulated radiation therapy (IMRT) was used in 720 patients (52.3%), volumetric modulated arc therapy was used in 45 patients (3.3%), stereotactic body radiation therapy (SBRT) in 113 patients (8.2%), and low–dose rate and high–dose rate brachytherapy (BT) were used in 305 patients (22.1%) and 195 patients (14.1%), respectively. Use of androgen deprivation therapy varied substantially among series. Biochemical disease-free survival at 5 years was reported for a cohort of 812 (58.9%) patients. The combined median biochemical disease-free survival for this group of patients was 85% (range: 78.8–100%; 95% confidence interval: 77.1–82.7%).

The average occurrence of grade III or worse gastrointestinal and genitourinary late toxicity was, respectively, 2.5% and 3.1% for intensity-modulated RT boost, 10% and 6% for stereotactic body RT, 6% and 2% for low–dose rate BT, and 4% and 4.3% for high–dose rate BT.

This review shows encouraging results for focal dose escalation to the IDN with acceptable short- to medium-term side effects and biochemical disease control rates. However, owing to the heterogeneity of patient population and the short follow-up, the results should be interpreted with caution. Considering that the clinical endpoint in the studies was biochemical recurrence, the use and duration of androgen deprivation therapy administration should be carefully considered before driving definitive conclusions. Randomized trials with long-term follow-up are needed before this technique can be generally recommended.

Radiotherapy combination opportunities leveraging immunity for the next oncology practice

Approximately one-half of patients with newly diagnosed cancer and many patients with persistent or recurrent tumors receive radiotherapy (RT), with the explicit goal of eliminating tumors through direct killing. The current RT dose and schedule regimens have been empirically developed. Although early clinical studies revealed that RT could provoke important responses not only at the site of treatment but also on remote, nonirradiated tumor deposits-the so-called "abscopal effect"- the underlying mechanisms were poorly understood and were not therapeutically exploited. Recent work has elucidated the immune mechanisms underlying these effects and has paved the way for developing combinations of RT with immune therapy. In the wake of recent therapeutic breakthroughs in the field of immunotherapy, rational combinations of immunotherapy with RT could profoundly change the standard of care for many tumor types in the next decade. Thus, a deep understanding of the immunologic effects of RT is urgently needed to design the next generation of therapeutic combinations. Here, the authors review the immune mechanisms of tumor radiation and summarize the preclinical and clinical evidence on immunotherapy-RT combinations. Furthermore, a framework is provided for the practicing clinician and the clinician investigator to guide the development of novel combinations to more rapidly advance this important field. CA Cancer J Clin 2017;67:65-85. © 2016 American Cancer Society.

Short Androgen Suppression and Radiation Dose Escalation for Intermediate- and High-Risk Localized Prostate Cancer: Results of EORTC Trial 22991

Purpose

Up to 30% of patients who undergo radiation for intermediate- or high-risk localized prostate cancer relapse biochemically within 5 years. We assessed if biochemical disease-free survival (DFS) is improved by adding 6 months of androgen suppression (AS; two injections of every-3-months depot of luteinizing hormone–releasing hormone agonist) to primary radiotherapy (RT) for intermediate- or high-risk localized prostate cancer.

Patients and Methods

A total of 819 patients staged: (1) cT1b-c, with prostate-specific antigen (PSA) ≥ 10 ng/mL or Gleason ≥ 7, or (2) cT2a (International Union Against Cancer TNM 1997), with no involvement of pelvic lymph nodes and no clinical evidence of metastatic spread, with PSA ≤ 50 ng/mL, were centrally randomized 1:1 to either RT or RT plus AS started on day 1 of RT. Centers opted for one dose (70, 74, or 78 Gy). Biochemical DFS, the primary end point, was defined from entry until PSA relapse (Phoenix criteria) and clinical relapse by imaging or death of any cause. The trial had 80% power to detect hazard ratio (HR), 0.714 by intent-to-treat analysis stratified by dose of RT at the two-sided α = 5%.

Results

The median patient age was 70 years. Among patients, 74.8% were intermediate risk and 24.8% were high risk. In the RT arm, 407 of 409 patients received RT; in the RT plus AS arm, 403 patients received RT plus AS and three patients received RT only. At 7.2 years median follow-up, RT plus AS significantly improved biochemical DFS (HR, 0.52; 95% CI, 0.41 to 0.66; P < .001, with 319 events), as well as clinical progression-free survival (205 events, HR, 0.63; 95% CI, 0.48 to 0.84; P = .001). In exploratory analysis, no statistically significant interaction between treatment effect and dose of RT could be evidenced (heterogeneity P = .79 and P = .66, for biochemical DFS and progression-free survival, respectively). Overall survival data are not mature yet.

Conclusion

Six months of concomitant and adjuvant AS improves biochemical and clinical DFS of intermediate- and high-risk cT1b-c to cT2a (with no involvement of pelvic lymph nodes and no clinical evidence of metastatic spread) prostatic carcinoma, treated by radiation.

Radiation Therapy after Radical Prostatectomy: Implications for Clinicians

Depending on the pathological findings, up to 60% of prostate cancer patients who undergo radical prostatectomy (RP) will develop biochemical relapse and require further local treatment. Radiotherapy (RT) immediately after RP may potentially eradicate any residual localized microscopic disease in the prostate bed, and it is associated with improved biochemical, clinical progression-free survival, and overall survival in patients with high-risk pathological features according to published randomized trials. Offering immediate adjuvant RT to all men with high-risk pathological factors we are over-treating around 50% of patients who would anyway be cancer-free, exposing them to unnecessary toxicity and adding costs to the health-care system. The current dilemma is, thus, whether to deliver adjuvant immediate RT solely on the basis of high-risk pathology, but in the absence of measurable prostate-specific antigen, or whether early salvage radiotherapy would yield equivalent outcomes. Randomized trials are ongoing to definitely answer this question. Retrospective analyses suggest that there is a dose–response favoring doses >70 Gy to the prostate bed. The evidence regarding the role of androgen deprivation therapy is emerging, and ongoing randomized trials are underway.

[(18)F]FDG-PET/CT metabolic parameters as useful prognostic factors in cervical cancer patients treated with chemo-radiotherapy

Background

To compare the prognostic value of different anatomical and functional metabolic parameters determined using [¹⁸F]FDG-PET/CT with other clinical and pathological prognostic parameters in cervical cancer (CC).

Methods

Thirty-eight patients treated with standard curative doses of chemo-radiotherapy (CRT) underwent pre- and post-therapy [¹⁸F]FDG-PET/CT. [¹⁸F]FDG-PET/CT parameters including mean tumor standardized uptake values (SUV), metabolic tumor volume (MTV) and tumor glycolytic volume (TGV) were measured before the start of CRT. The post-treatment tumor metabolic response was evaluated. These parameters were compared to other clinical prognostic factors. Survival curves were estimated by using the Kaplan-Meier method. Cox regression analysis was performed to determine the independent contribution of each prognostic factor.

Results

After 37 months of median follow-up (range, 12–106), overall survival (OS) was 71 % [95 % confidence interval (CI), 54–88], disease-free survival (DFS) 61 % [95 % CI, 44–78] and loco-regional control (LRC) 76 % [95 % CI, 62–90]. In univariate analyses the [¹⁸F]FDG-PET/CT parameters unfavorably influencing OS, DFS and LRC were pre-treatment TGV-cutoff ≥562 (37 vs. 76 %, p = 0.01; 33 vs. 70 %, p = 0.002; and 55 vs. 83 %, p = 0.005, respectively), mean pre-treatment tumor SUV cutoff ≥5 (57 vs. 86 %, p = 0.03; 36 vs. 88 %, p = 0.004; 65 vs. 88 %, p = 0.04, respectively) and a partial tumor metabolic response after treatment (9 vs. 29 %, p = 0.0008; 0 vs. 83 %, p < 0.0001; 22 vs. 96 %, p < 0.0001, respectively). After multivariate analyses a partial tumor metabolic response after treatment remained as an independent prognostic factor unfavorably influencing DFS and LRC (RR 1:7.7, p < 0.0001, and RR 1:22.6, p = 0.0003, respectively) while the pre-treatment TGV-cutoff ≥562 negatively influenced OS and DFS (RR 1:2, p = 0.03, and RR 1:2.75, p = 0.05).

Conclusions

Parameters capturing the pre-treatment glycolytic volume and metabolic activity of [¹⁸F]FDG–positive disease provide important prognostic information in patients with CC treated with CRT. The post-therapy [¹⁸F]FDG-PET/CT uptake (partial tumor metabolic response) is predictive of disease outcome.

Consensus and differences in primary radiotherapy for localized and locally advanced prostate cancer in Switzerland: A survey on patterns of practice

INTRODUCTION

External beam radiotherapy (EBRT), with or without androgen deprivation therapy (ADT), is an established treatment option for nonmetastatic prostate cancer. Despite high-level evidence from several randomized trials, risk group stratification and treatment recommendations vary due to contradictory or inconclusive data, particularly with regard to EBRT dose prescription and ADT duration. Our aim was to investigate current patterns of practice in primary EBRT for prostate cancer in Switzerland.

MATERIALS AND METHODS

Treatment recommendations on EBRT and ADT for localized and locally advanced prostate cancer were collected from 23 Swiss radiation oncology centers. Written recommendations were converted into center-specific decision trees, and analyzed for consensus and differences using a dedicated software tool. Additionally, specific radiotherapy planning and delivery techniques from the participating centers were assessed.

RESULTS

The most commonly prescribed radiation dose was 78 Gy (range 70-80 Gy) across all risk groups. ADT was recommended for intermediate-risk patients for 6 months in over 80 % of the centers, and for high-risk patients for 2 or 3 years in over 90 % of centers. For recommendations on combined EBRT and ADT treatment, consensus levels did not exceed 39 % in any clinical scenario. Arc-based intensity-modulated radiotherapy (IMRT) is implemented for routine prostate cancer radiotherapy by 96 % of the centers.

CONCLUSION

Among Swiss radiation oncology centers, considerable ranges of radiotherapy dose and ADT duration are routinely offered for localized and locally advanced prostate cancer. In the vast majority of cases, doses and durations are within the range of those described in current evidence-based guidelines.

Long-term outcome and late side effects in endometrial cancer patients treated with surgery and postoperative radiation therapy

BACKGROUND

We retrospectively reviewed the long-term outcome and late side effects of endometrial cancer (EC) patients treated with different techniques of postoperative radiotherapy (PORT).

METHODS

Between 1999 and 2012, 237 patients with EC were treated with PORT. Two-dimensional external beam radiotherapy (2D-EBRT) was used in 69 patients (30 %), three-dimensional EBRT (3D-EBRT) in 51 (21 %), and intensity-modulated RT (IMRT) with helical Tomotherapy in 47 (20 %). All patients received a vaginal brachytherapy (VB) boost. Seventy patients (29 %) received VB alone.

RESULTS

After a median of 68 months (range, 6-154) of follow-up, overall survival was 75 % [95 % confidence interval (CI), 69-81], disease-free survival was 72 % (95% CI, 66-78), cancer-specific survival was 85 % (95 % CI, 80-89), and locoregional control was 86 % (95 % CI, 81-91). The 5-year estimates of grade 3 or more toxicity and second cancer rates were 0 and 7 % (95 % CI, 1-13) for VB alone, 6 % (95 % CI, 1-11) and 0 % for IMRT + VB, 9 % (95 % CI, 1-17) and 5 % (95 % CI, 1-9) for 3D-EBRT + VB, and 22 % (95 % CI, 12-32) and 12 % (95 % CI, 4-20) for 2D-EBRT + VB (P = 0.002 and P = 0.01), respectively.

CONCLUSIONS

Pelvic EBRT should be tailored to patients with high-risk EC because the severe late toxicity observed might outweigh the benefits. When EBRT is prescribed for EC, IMRT should be considered, because it was associated with a significant reduction of severe late side effects.

The role of PET/CT in cervical cancer

In locally advanced cervical cancer, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography – computed tomography (PET/CT) has become important in the initial evaluation of disease extent. It is superior to other imaging modalities for lymph node status and distant metastasis. PET-defined cervical tumor volume predicts progression-free and overall survival. Higher FDG uptake in both primary and regional lymph nodes is strongly predictive of worse outcome. FDG-PET is useful for assessing treatment response 3 months after completing concurrent chemo-radiotherapy (CRT) and predicting long-term survival, and in suspected disease recurrence. In the era of image-guided adaptive radiotherapy, accurately defining disease areas is critical to avoid irradiating normal tissue. Based on additional information provided by FDG-PET, radiation treatment volumes can be modified and higher doses to FDG-positive lymph nodes safely delivered. FDG-PET/CT has been used for image-guided brachytherapy of FDG-avid tumor volume, while respecting low doses to bladder and rectum. Despite survival improvements due to CRT in cervical cancer, disease recurrences continue to be a major problem. Biological rationale exists for combining novel non-cytotoxic agents with CRT, and drugs targeting specific molecular pathways are under clinical development. The integration of these targeted therapies in clinical trials, and the need for accurate predictors of radio-curability is essential. New molecular imaging tracers may help identifying more aggressive tumors. ⁶⁴Cu-labeled diacetyl-di(N(4)-methylthiosemicarbazone) is taken up by hypoxic tissues, which may be valuable for prognostication and radiation treatment planning. PET/CT imaging with novel radiopharmaceuticals could further impact cervical cancer treatment as surrogate markers of drug activity at the tumor microenvironment level. The present article reviews the current and emerging role of PET/CT in the management of cervical cancer.

Retrospective feasibility study of simultaneous integrated boost in cervical cancer using Tomotherapy: the impact of organ motion and tumor regression

Background

Whole pelvis intensity modulated radiotherapy (IMRT) is increasingly being used to treat cervical cancer aiming to reduce side effects. Encouraged by this, some groups have proposed the use of simultaneous integrated boost (SIB) to target the tumor, either to get a higher tumoricidal effect or to replace brachytherapy. Nevertheless, physiological organ movement and rapid tumor regression throughout treatment might substantially reduce any benefit of this approach.

Purpose

To evaluate the clinical target volume - simultaneous integrated boost (CTV-SIB) regression and motion during chemo-radiotherapy (CRT) for cervical cancer, and to monitor treatment progress dosimetrically and volumetrically to ensure treatment goals are met.

Methods and materials

Ten patients treated with standard doses of CRT and brachytherapy were retrospectively re-planned using a helical Tomotherapy - SIB technique for the hypothetical scenario of this feasibility study. Target and organs at risk (OAR) were contoured on deformable fused planning-computed tomography and megavoltage computed tomography images. The CTV-SIB volume regression was determined. The center of mass (CM) was used to evaluate the degree of motion. The Dice’s similarity coefficient (DSC) was used to assess the spatial overlap of CTV-SIBs between scans. A cumulative dose-volume histogram modeled estimated delivered doses.

Results

The CTV-SIB relative reduction was between 31 and 70%. The mean maximum CM change was 12.5, 9, and 3 mm in the superior-inferior, antero-posterior, and right-left dimensions, respectively. The CTV-SIB-DSC approached 1 in the first week of treatment, indicating almost perfect overlap. CTV-SIB-DSC regressed linearly during therapy, and by the end of treatment was 0.5, indicating 50% discordance. Two patients received less than 95% of the prescribed dose. Much higher doses to the OAR were observed. A multiple regression analysis showed a significant interaction between CTV-SIB reduction and OAR dose increase.

Conclusions

The CTV-SIB had important regression and motion during CRT, receiving lower therapeutic doses than expected. The OAR had unpredictable shifts and received higher doses. The use of SIB without frequent adaptation of the treatment plan exposes cervical cancer patients to an unpredictable risk of under-dosing the target and/or overdosing adjacent critical structures. In that scenario, brachytherapy continues to be the gold standard approach.

Molecular targeted agents combined with chemo-radiation in the treatment of locally advanced cervix cancer

Despite improvements in survival after the introduction of chemo-radiotherapy (CRT) in the treatment of patients with cervical cancer, loco-regional control of this disease continues to be a major problem. The present article reviews current and emerging therapeutic strategies combining CRT with novel molecular agents that specifically target the abnormal tumor microenvironment, with the aim of improving local control and survival in patients with locally advanced cervix cancer. The evidence supporting the biological rational to combine novel non-cytotoxic agents with CRT is strong, and drugs targeting different molecular pathways are currently under clinical development (EGFR inhibitors, COX-2 inhibitors, hypoxia targeted agents, etc). Early pre-clinical and clinical strategies also favor the use of vascular-targeted agents with the aim to normalize the abnormal tumor vasculature, increase tumor oxygenation, and reduce interstitial fluid pressure (IFP). The integration of these novel targeted therapies with CRT in clinical trials is discussed, as well as new and promising biomarkers to test drug activity.

A prospective phase I–II trial of the cyclooxygenase-2 inhibitor celecoxib in patients with carcinoma of the cervix with biomarker assessment of the tumor microenvironment

PURPOSE

To evaluate the toxicity and effectiveness of celecoxib in combination with definitive chemoradiotherapy (CRT) in women with locally advanced cervical cancer.

METHODS AND MATERIALS

Thirty-one patients were accrued to a phase I-II trial of celecoxib 400 mg by mouth twice per day for 2 weeks before and during CRT. Tumor oxygenation (HP(5)) and interstitial fluid pressure (IFP) were measured before and 2 weeks after celecoxib administration alone. The median follow-up time was 2.7 years (range, 1.1-4.4 years).

RESULTS

The most common acute G3/4 toxicities were hematologic (4/31, 12.9%) and gastrointestinal (5/31, 16.1%) largely attributed to chemotherapy. Late G3/4 toxicity was seen in 4 of 31 patients (13.7% actuarial risk at 2 yr), including fistulas in 3 patients (9.7%). Within the first year of follow-up, 25 of 31 patients (81%) achieved complete response (CR), of whom 20 remained in CR at last follow-up. After 2 weeks of celecoxib administration before CRT, the median IFP decreased slightly (median absolute, -4.6 mm Hg; p = 0.09; relative, -21%; p = 0.07), whereas HP(5) did not change significantly (absolute increase, 3.6%; p = 0.51; median relative increase, 11%; p = 0.27). No significant associations were seen between changes in HP(5) or IFP and response to treatment (p = 0.2, relative HP(5) change and p = 0.14, relative IFP change).

CONCLUSIONS

Celecoxib in combination with definitive CRT is associated with acceptable acute toxicity, but higher than expected late complications. Celecoxib is associated with a modest reduction in the angiogenic biomarker IFP, but this does not correspond with tumor response.