Low-Dose Radiotherapy as a Chemopotentiator of Gemcitabine in Tumors of the Pancreas or Small Bowel: A Phase I Study Exploring a New Treatment Paradigm

Whole-body CT scanning radiation improves the immune microenvironment of tumor tissues to enhance the antitumor effect of ICI

OBJECTIVE

The effect of frequent whole-body CT scans during immune checkpoint inhibitor (ICI) therapy on patients' anti-tumor immunity.

METHODS

We conducted a retrospective clinical study aimed to investigate the correlation between the frequency of CT scans during immune checkpoint inhibitor (ICI) therapy and the duration of remission (DOR) of ICI therapy in patients with stage IV non-small cell lung cancer (NSCLC). We constructed a hormonal mouse model and administered immune checkpoint inhibitor (ICI) therapy to mice, and radiated five whole-body CT scans to mice during ICI therapy to observe whether frequent whole-body CT scans had an effect on the antitumor effect of immunotherapy in mice.

RESULTS

The more frequent CT scans during patients' immune checkpoint inhibitor (ICI) treatment the longer the duration of remission (DOR) of ICI treatment. In a mouse model we observed that the addition of whole-body CT scanning radiation had a tendency to inhibit tumor growth in mice compared with the anti-PD-1 group alone.Frequent CT scanning radiation during the application of immune checkpoint inhibitor PD-1 increased the proportion of infiltrating CD8 + T cells in tumor tissues and significantly increased the proportion of IFNγ-secreting CD8 + T cells, and single-cell sequencing of the results also revealed that IFNγ and killing-related genes were significantly upregulated in tumor-infiltrating CD8T cells.

CONCLUSION

To our knowledge this is the first study on the effect of CT scan radiation on ICI.Our findings suggest that multiple CT scans during immune checkpoint inhibitor (ICI) treatment did not promote tumor progression, but instead a trend toward delayed tumor progression was observed.

Combined treatment of small cell lung cancer using radiotherapy and immunotherapy: Challenges and updates

Currently, chemotherapy remains the standard first- and second-line treatment for small cell lung cancer (SCLC). Research concerning immunotherapy has brought about a remarkable development in the treatment pattern of SCLC. Atirizumab, duvalizumab, atezolizumab, and serplulimab can significantly improve the clinical outcomes of SCLC. Given the rapidly evolving concept that combining immunotherapy with radiotherapy can increase therapeutic effectiveness, clinicians are devoted to further improving local tumor control by integrating immunotherapy with radiotherapy. This paper reviews the research progress in this field to date and explores ways to further enhance the efficacy of this combination therapy. We first discussed that immunotherapy combined with radiotherapy can improve the abscopal effect, progression-free survival, and overall survival rates of SCLC patients. Then, the biomarkers related to the radiation immune microenvironment, such as programmed death ligand-1 (PD-L1), tumor mutational burden (TMB), and the immune function of patients were discussed. Next, we explored the occurrence and underlying mechanisms of immune resistance during radiotherapy implementation. Finally, we clarified that the emerging trend of low-dose radiotherapy help overcome the inhibitory signals that limit T-cell infiltration in the tumor matrix. In summary, considering the rapid development of this field, these combined therapy strategies may have unlimited potential to further improve the efficacy of radiotherapy combined with immunotherapy for patients.

Strategies for overcoming tumour resistance to immunotherapy: harnessing the power of radiation therapy

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment; yet their efficacy remains variable across patients. This review delves into the intricate interplay of tumour characteristics contributing to resistance against ICI therapy and suggests that combining with radiotherapy holds promise. Radiation, known for its ability to trigger immunogenic cell death and foster an in situ vaccination effect, may counteract these resistance mechanisms, enhancing ICI response and patient outcomes. However, particularly when delivered at high-dose, it may trigger immunosuppressive mechanism and consequent side-effects. Notably, low-dose radiotherapy (LDRT), with its capacity for tumour reprogramming and reduced side effects, offers the potential for widespread application. Preclinical and clinical studies have shown encouraging results in this regard.

Low-dose radiation therapy mobilizes antitumor immunity: New findings and future perspectives

Radiotherapy has unique immunostimulatory and immunosuppressive effects. Although high-dose radiotherapy has been found to have systemic antitumor effects, clinically significant abscopal effects were uncommon on the basis of irradiating single lesion. Low-dose radiation therapy (LDRT) emerges as a novel approach to enhance the antitumor immune response due to its role as a leverage to reshape the tumor immune microenvironment (TIME). In this article, from bench to bedside, we reviewed the possible immunomodulatory role of LDRT on TIME and systemic tumor immune environment, and outlined preclinical evidence and clinical application. We also discussed the current challenges when LDRT is used as a combination therapy, including the optimal dose, fraction, frequency, and combination of drugs. The advantage of low toxicity makes LDRT potential to be applied in multiple lesions to amplify antitumor immune response in polymetastatic disease, and its intersection with other disciplines might also make it a direction for radiotherapy-combined modalities.

Opportunities and challenges in combining immunotherapy and radiotherapy in esophageal cancer

BACKGROUND

Immunotherapy has shown promise in the treatment of esophageal cancer, but using it alone only benefits a small number of patients. Most patients either do not have a significant response or develop secondary drug resistance. The combination of radiotherapy and immunotherapy appears to be a promising approach to treating esophageal cancer.

PURPOSE

We reviewed milestone clinical trials of radiotherapy combined with immunotherapy for esophageal cancer. We then discussed potential biomarkers for radiotherapy combined with immunotherapy, including programmed cell death-ligand 1 (PD-L1) status, tumor mutation burden (TMB), tumor-infiltrating lymphocytes, ct-DNA, imaging biomarkers, and clinical factors. Furthermore, we emphasize the key mechanisms of radiation therapy-induced immune stimulation and immune suppression in order to propose strategies for overcoming immune resistance in radiation therapy (RT). Lastly, we discussed the emerging role of low-dose radiotherapy (LDRT) , which has become a promising approach to overcome the limitations of high-dose radiotherapy.

CONCLUSION

Radiotherapy can be considered a triggering factor for systemic anti-tumor immune response and, with the assistance of immunotherapy, can serve as a systemic treatment option and potentially become the standard treatment for cancer patients.

Exploring low-dose radiotherapy to overcome radio-immunotherapy resistance

Immune checkpoint inhibitors (ICIs) have revolutionized the current treatment landscape for cancer, yet the response rates of ICIs remain unmet. Synergistic with immunotherapy, low-dose radiotherapy (LDRT) has been demonstrated to activate anti-tumor immunity - a transition from traditional radiation therapy geared toward local radical treatment to a type of immunological adjuvant. As such, studies utilizing LDRT to enhance the efficacy of immunotherapy have been increasing preclinically and clinically. This paper reviews the recent strategies of using LDRT to overcome the resistance of ICIs, as well as providing potential opportunities in cancer treatment. Despite the potential of LDRT in immunotherapy is recognized, the mechanisms behind this form of treatment remain largely elusive. Thus, we reviewed history, mechanisms and challenges associated with this form of treatment, as well as different modes of its application, to provide relatively accurate practice standards for LDRT as a sensitizing treatment when combined with immunotherapy or radio-immunotherapy.

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.

Clinical Studies on Ultrafractionated Chemoradiation: A Systematic Review

Aim

The efficacy of low-dose fractionated radiotherapy (LDFRT) and chemotherapy (CHT) combination has large preclinical but little clinical evidence. Therefore, the aim of this review was to collect and analyze the clinical results of LDRT plus concurrent CHT in patients with advanced cancers.

Methods

A systematic literature search was conducted on PubMed using the PRISMA methodology. Only studies based on the combination of LDFRT (< 1 Gy/fraction) and CHT were included. Endpoints of the analysis were tumor response, toxicity, and overall survival, with particular focus on any differences between LDFRT-CHT and CHT alone.

Results

Twelve studies (307 patients) fulfilled the selection criteria and were included in this review. Two studies were retrospective, one was a prospective pilot trial, six were phase II studies, two were phase I trials, and one was a phase I/II open label study. No randomized controlled trials were found. Seven out of eight studies comparing clinical response showed higher rates after LDFRT-CHT compared to CHT alone. Three out of four studies comparing survival reported improved results after combined treatment. Three studies compared toxicity of CHT and LDFRT plus CHT, and all of them reported similar adverse events rates. In most cases, toxicity was manageable with only three likely LDFRT-unrelated fatal events (1%), all recorded in the same series on LDFRT plus temozolomide in glioblastoma multiforme patients.

Conclusion

None of the analyzed studies provided level I evidence on the clinical impact of LDFRT plus CHT. However, it should be noted that, apart from two small series of breast cancers, all studies reported improved therapeutic outcomes and similar tolerability compared to CHT alone.

Systematic Review Registration

www.crd.york.ac.uk/prospero/, identifier CRD42020206639.

Combined treatment of non-small cell lung cancer using radiotherapy and immunotherapy: challenges and updates

The efficacy of immunotherapy for advanced non‐small cell lung cancer (NSCLC) remains unsatisfactory, as the majority of patients either do not experience an objective response or acquire secondary resistance. As a result, several methods to enhance the systemic efficacy of immunotherapy have been investigated, including a large area of active research by combining immunotherapy with radiation therapy (RT). Given the rapidly burgeoning concept of combining immunotherapy and RT for increasing therapeutic benefit, we review the progress in this field thus far and explore further avenues for enhancing this combination. This review commences with a discussion of the only two existing randomized trials (and a pooled analysis) showing that the addition of RT to immunotherapy improves the abscopal response rate, progression‐free survival, and overall survival in metastatic NSCLC patients. We then discussed factors and biomarkers that may be associated with a proportionally greater benefit to additional RT, such as low programmed cell death protein ligand 1 (PD‐L1) status, tumor mutational burden (TMB), and patient's immune function. Next, the implementation of RT to overcome immunotherapy resistance is discussed, including a mechanistic discussion and methods with which these mechanisms could be exploited. Lastly, the emerging role of low‐dose RT is discussed, which may help to overcome inhibitory signals in the tumor stroma that limit T‐cell infiltration. Taken together, given the current state of this rapidly expanding realm, these futuristic strategies may be reflected upon to further enhance the efficacy of immunotherapy for a wider group of patients.

High-dose irradiation in combination with non-ablative low-dose radiation to treat metastatic disease after progression on immunotherapy: Results of a phase II trial

AIM

To report early findings from a phase II trial of high-dose radiotherapy (HD-RT) with or without low-dose RT (LD-RT) for metastatic cancer.

METHODS

Eligible patients had metastatic disease that progressed on immunotherapy within 6 months. Patients were given either HD-RT (20-70 Gy total; 3-12.5 Gy/f), or HD-RT + LD-RT (0.5-2 Gy/f up to 1-10 Gy total) to separate lesions, with continued immunotherapy. Radiographic response was assessed per RECIST 1.1 and Immune-Related Response Criteria (irRC). Primary endpoints: (1) 4-month disease control (DCR, complete/partial response [CR/PR] or stable disease [SD]) or an overall response (ORR, CR/PR) at any point in ≥10% of patients, per RECIST 1.1; (2) dose-limiting toxicity within 3 months not exceeding 30%. Secondary endpoint was lesion-specific response.

RESULTS

Seventy-four patients (NSCLC, n = 38; melanoma n = 21) were analyzed (39 HD-RT and 35 HD-RT + LD-RT). The median follow-up time was 13.6 months. The primary endpoint was met for 72 evaluable patients, with a 4-month DCR of 42% (47% [16/34] vs. 37% [14/38] in HD-RT + LD-RT vs. HD-RT, P = 0.38), and 19% ORR at any time (26% [9/34] vs. 13% [5/38] in HD-RT + LD-RT vs. HD-RT, P = 0.27). Three patients had toxicity ≥grade 3. LD-RT lesion response (53%) was improved compared to nonirradiated lesions in HD-RT + LD-RT (23%, P = 0.002) and HD-RT (11%, P < 0.001). T- and NK cell infiltration was enhanced in lesions treated with LD-RT.

CONCLUSIONS

HD-RT plus LD-RT safely improved lesion-specific response in patients with immune resistant solid tumors by promoting infiltration of effector immune cells into the tumor microenvironment.

DUOX2, a New Biomarker for Disseminated Gastric Cancer's Response to Low Dose Radiation in Mice

Treatment options are rather limited for gastrointestinal cancer patients whose disease has disseminated into the intra-abdominal cavity. Here, we designed pre-clinical studies to evaluate the potential application of chemopotentiation by Low Dose Fractionated Radiation Therapy (LDFRT) for disseminated gastric cancer and evaluate the role of a likely biomarker, Dual Oxidase 2 (DUOX2). Nude mice were injected orthotopically with human gastric cancer cells expressing endogenous or reduced levels of DUOX2 and randomly assigned to four treatment groups: 1; vehicle alone, 2; modified regimen of docetaxel, cisplatin and 5'-fluorouracil (mDCF) for three consecutive days, 3; Low Dose- Whole Abdomen Radiation Therapy (LD-WART) (5 fractions of 0.15 Gy in three days), 4; mDCF and LD-WART. The combined regimen increased the odds of preventing cancer dissemination (mDCF + LD-WART OR = 4.16; 80% CI = 1.0, 17.29) in the DUOX2 positive tumors, while tumors expressing lower DUOX2 levels were more responsive to mDCF alone with no added benefit from LD-WART. The molecular mechanisms underlying DUOX2 effects in response to the combined regimen include NF-κB upregulation. These data are particularly important since our study indicates that about 33% of human stomach adenocarcinoma do not express DUOX2. DUOX2 thus seems a likely biomarker for potential clinical application of chemopotentiation by LD-WART.

Chemopotentiation by Ultrafractionated Radiotherapy in Glioblastoma Resistant to Conventional Therapy

Introduction

Induced radiation resistance (IRR) and hyper-radiosensitivity (HRS) are well-described phenomena in basic literature, yet few reports have been published in which such phenomena are exploited clinically for the benefit of patients. Glioblastoma is a prime example.

Case and methods

The case of an 82-year-old woman is described whose resected frontoparietal glioblastoma progressed through treatment administered according to standard methods. With review board and patient approval, we continued her treatment using radiotherapy and temozolomide, but drastically modified the radiotherapy fractionation, administering 50 cGy twice daily on each of the first 5 days of a 14-day cycle. Temozolomide was administered on the first 4 days of each cycle. We use the term “ultrafractionated radiotherapy” to refer to the extremely low doses of radiation used in this case.

Results

This modified regimen resulted in regression of the contrast-enhancing areas of disease recurrence identified on MRI, and the patient survived approximately 6 months following recurrence of her disease, having received 5 cycles of additional therapy after prior full-dose treatment.

Conclusions

Ultrafractionated radiotherapy and concurrent temozolomide were efficacious and tolerable in this patient whose glioblastoma previously progressed through conventional treatment. Additional studies of this approach are warranted. Free full text available at www.tumorionline.it

Radiation Treatment in Women with Ovarian Cancer: Past, Present, and Future

Ovarian cancer is the most lethal of the gynecologic cancers, with 5-year survival rates less than 50%. Most women present with advanced stage disease as the pattern of spread is typically with dissemination of malignancy throughout the peritoneal cavity prior to development of any symptoms. Prior to the advent of platinum-based chemotherapy, radiotherapy was used as adjuvant therapy to sterilize micrometastatic disease. The evolution of radiotherapy is detailed in this review, which establishes radiotherapy as an effective therapy for women with micrometastatic disease in the peritoneal cavity after surgery, ovarian clear cell carcinoma, focal metastatic disease, and for palliation of advanced disease. However, with older techniques, the toxicity of whole abdominal radiotherapy and the advancement of systemic therapies have limited the use of radiotherapy in this disease. With newer radiotherapy techniques, including intensity-modulated radiotherapy (IMRT), stereotactic body radiotherapy (SBRT), and low-dose hyperfractionation in combination with targeted agents, radiotherapy could be reconsidered as part of the standard management for this deadly disease.

A final report of a phase I study of veliparib (ABT-888) in combination with low-dose fractionated whole abdominal radiation therapy (LDFWAR) in patients with advanced solid malignancies and peritoneal carcinomatosis with a dose escalation in ovarian and fallopian tube cancers

BACKGROUND

The combination of low-dose radiation therapy with PARP inhibition enhances anti-tumor efficacy through potentiating DNA damage. We combined low-dose fractionated whole abdominal radiation (LDFWAR) with ABT-888 in patients with peritoneal carcinomatosis with a dose escalation in ovarian and fallopian cancer patients (OV).

METHODS

Patients were treated with veliparib, 40-400mg orally BID on days 1-21 of 3 28-day cycles on 6 dose levels. Dose levels 5 and 6 included only OV patients. LDFWAR consisted of 21.6Gy in 36 fractions, 0.6Gy twice daily on days 1 and 5 for weeks 1-3 of each cycle. Circulating tumor material and quality of life were serially assessed.

RESULTS

32pts were treated. Median follow-up was 45months (10-50). The most common treatment-related grade 3 and 4 toxicities were lymphopenia (59%), anemia (9%), thrombocytopenia (12%), neutropenia (6%), leukopenia (6%), nausea (6%), diarrhea (6%), anorexia (6%), vomiting (6%) and fatigue (6%). The maximum tolerated dose was determined to be 250mg PO BID. Median PFS was 3.6months and median OS was 9.1months. In OV patients, OS was longer for platinum-sensitive patients (10.9mo) compared to platinum-resistant patients (5.8mo). QoL decreased for all groups during treatment. Germline BRCA status was known for 14/18 patients with OV cancers, 5 of whom were BRCA mutation carriers. One objective response (3%) was observed.

CONCLUSION

ABT-888 plus LDFWAR is tolerable with gastrointestinal symptoms, fatigue and myelosuppression as the most common toxicities. The single observed objective response was in a germline BRCA mutated, platinum-sensitive patient.

Autophagy influences the low-dose hyper-radiosensitivity of human lung adenocarcinoma cells by regulating MLH1

PURPOSE

To investigate the impact of autophagy on the low-dose hyper-radiosensitivity (HRS) of human lung adenocarcinoma cells via MLH1 regulation.

MATERIALS AND METHODS

Immunofluorescent staining, Western blotting, and electron microscopy were utilized to detect autophagy in A549 and H460 cells. shRNA was used to silence MLH1 expression. The levels of MLH1, mTOR, p-mTOR, BNIP3, and Beclin-1 were measured by real-time polymerase chain reaction (PCR) and Western blotting.

RESULTS

A549 cells, which have low levels of MLH1 expression, displayed HRS/induced radioresistance (IRR). Conversely, the radiosensitivity of H460 cells, which express high levels of MLH1, conformed to the linear-quadratic (LQ) model. After down-regulating MLH1 expression, A549 cells showed increased HRS and inhibition of autophagy, whereas H460 cells exhibited HRS/IRR. The levels of mTOR, p-mTOR, and BNIP3 were reduced in cells harboring MLH1 shRNA, and the changes in the mTOR/p-mTOR ratio mirrored those in MLH1 expression.

CONCLUSIONS

Low MLH1-expressing A549 cells may exhibit HRS. Both the mTOR/p-mTOR and BNIP3/Beclin-1 signaling pathways were found to be related to HRS, but only mTOR/p-mTOR is involved in the regulation of HRS via MLH1 and autophagy.

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.

Effect of Irradiation on Tissue Penetration Depth of Doxorubicin after Pressurized Intra-Peritoneal Aerosol Chemotherapy (PIPAC) in a Novel Ex-Vivo Model

Background: This study was performed to assess the impact of irradiation on the tissue penetration depth of doxorubicin delivered during Pressurized Intra-Peritoneal Aerosol Chemotherapy (PIPAC).

Methods: Fresh post mortem swine peritoneum was cut into 10 proportional sections. Except for 2 control samples, all received irradiation with 1, 2, 7 and 14 Gy, respectively. Four samples received PIPAC 15 minutes after irradiation and 4 other after 24 hours. Doxorubicin was aerosolized in an ex-vivo PIPAC model at 12 mmHg/36°C. In-tissue doxorubicin penetration was measured using fluorescence microscopy on frozen thin sections.

Results: Doxorubicin penetration after PIPAC (15 minutes after irradiation) was 476 ± 74 µm for the control sample, 450 ± 45µm after 1 Gy (p > 0.05), 438 ± 29 µm after 2 Gy (p > 0.05), 396 ± 32 µm after 7 Gy (p = 0.005) and 284 ± 57 after 14 Gy irradiation (p < 0.001). The doxorubicin penetration after PIPAC (24 hours after irradiation) was 428 ± 77 µm for the control sample, 393 ± 41 µm after 1 Gy (p > 0.05), 379 ± 56 µm after 2 Gy (p > 0.05), 352 ± 53 µm after 7 Gy (p = 0.008) and 345 ± 53 after 14 Gy irradiation (p = 0.001).

Conclusions: Higher (fractional) radiation dose might reduce the tissue penetration depth of doxorubicin in our ex-vivo model. However, irradiation with lower (fractional) radiation dose does not affect the tissue penetration negatively. Further studies are warranted to investigate if irradiation can be used safely as chemopotenting agent for patients with peritoneal metastases treated with PIPAC.

Low-dose radiotherapy and concurrent FOLFIRI-bevacizumab: a Phase II study

Aims: Low-dose radiation therapy (LDRT) can increase biological efficacy of chemotherapy. This Phase II trial evaluates LDRT plus FOLFIRI-bevacizumab (FOLFIRI-B) in metastatic colorectal cancer. Materials & methods: Primary objective: raising the clinical complete response rate from 5 to 25%. Secondary objectives: toxicity, progression-free survival. Patients underwent 12 FOLFIRI-B cycles plus two daily LDRT fractions (20 cGy/6 h interval) on each cycle. Statistical analysis was planned on 18 patients. Results: Results on 18 patients are reported. Specifically considering irradiated sites: 15/18 patients had a partial (11/18) or complete (4/18) response. Among 11 partial responders, three became a pathological CR after surgery. Grade 3–4 toxicity was recorded in two patients (11.1%). At median follow-up of 30 months (range: 8-50), 7/18 patients progressed in irradiated sites. Conclusion: Seven out of 18 patients (38.9%) had clinical or pathological CR in lesions treated with LDRT. Further studies on this newer treatment modality seem justified.

Chemically enhanced radiotherapy: visions for the future

Radiotherapy (RT) is an important part of cancer management, with more than a third of all cancer cures being attributable to RT. Despite the advances in RT over the past century, the overall outcomes in a majority of malignancies are still unsatisfactory. There has been a constant endeavor to enhance the outcome of RT, and this has been in the form of altered fractionation, oxymimetic radiosensitizers, the use of concurrent chemotherapy, anti-angiogenic therapy and anti-growth factor receptor targeted therapies. This article presents a vision for the future, with emphasis upon emerging prospects which could enhance RT outcomes. Positive speculations regarding the use of immunological aspects, the use of nanoscale technology and the adoption of metronomic concurrent chemotherapy have been presented. Also, the potential with the use of low dose hyperradiosensitivity in enhancing chemotherapy outcomes too has been discussed. In this era of evidence based clinical practise, there exists a strong obsession towards the 'present' with 'contempt towards the future'. Accepting the shortcomings of the existing modalities, there must be a strong zeal towards discovering better methodologies to enhance radiotherapeutic outcomes for the sake of a better future.

A Phase I study of veliparib (ABT-888) in combination with low-dose fractionated whole abdominal radiation therapy in patients with advanced solid malignancies and peritoneal carcinomatosis

PURPOSE

The combination of low-dose radiotherapy with PARP inhibition has been shown to enhance antitumor efficacy through potentiating DNA damage. We combined low-dose fractionated whole abdominal radiation (LDFWAR) with escalating doses of veliparib (ABT-888), a small-molecule PARP inhibitor, in patients with peritoneal carcinomatosis from advanced solid tumor malignancies.

EXPERIMENTAL DESIGN

Patients were treated with veliparib (80-320 mg daily) for a total of 3 cycles. LDFWAR consisted of 21.6 Gy in 36 fractions, 0.6 Gy twice daily on days 1 and 5 for weeks 1-3 of each cycle. Circulating tumor cells (CTC) were collected and evaluated for γ-H2AX. Quality of life (QoL) was assessed using the EORTC-QLQ-C30 questionnaire.

RESULTS

Twenty-two patients were treated. Treatment-related grade 3 and 4 toxicities included lymphopenia (68%), anemia (9%), thrombocytopenia (14%), neutropenia (4%), leukopenia (9%), ascites (4%), vomiting (4%), and dyspnea (4%). No objective responses were observed. Disease stabilization (≥24 weeks) was observed in 7 patients (33%). Median progression-free survival (mPFS) was 4.47 months and median overall survival (mOS) was 13.04 months. In the subset of 8 ovarian and fallopian cancers, mPFS was 6.77 months and mOS was 17.54 months compared with mPFS 2.71 months and mOS 13.01 months in others. Patients with ovarian and fallopian cancers had better QoL over time than those with other cancers. An increased percentage of γ-H2AX-positive CTCs was observed in a subset of patients (3/6 with >2 CTCs at baseline).

CONCLUSIONS

Combined veliparib and LDFWAR is a well-tolerated regimen that resulted in prolonged disease stability for some patients with advanced solid tumors and carcinomatosis, particularly in the ovarian and fallopian cancer subpopulation.

Multi-institutional phase I study of low-dose ultra-fractionated radiotherapy as a chemosensitizer for gemcitabine and erlotinib in patients with locally advanced or limited metastatic pancreatic cancer

PURPOSE

Gemcitabine (G) has been shown to sensitize pancreatic cancer to radiotherapy but requires lower doses of G and thus delays aggressive systemic treatment, potentially leading to distant failure. We initiated a phase I trial combining ultra-fractionated low-dose radiotherapy with full dose G and erlotinib in the treatment of patients with advanced pancreatic cancer.

METHODS

Patients with locally advanced or metastatic pancreatic cancer confined to the abdomen and an ECOG performance status (PS) of 0-1 who had received 0-1 prior regimens (without G or E) and no prior radiotherapy were eligible. Patients were treated in 21 day cycles with G IV days 1 & 8, E once PO QD, and twice daily RT fractions separated by at least 4h on days 1, 2, 8, and 9. Whole abdominal RT fields were used. Primary endpoint was to define dose limiting toxicity (DLT) and the maximum tolerated dose (MTD).

RESULTS

27 patients (median age 64 years and 15 male) were enrolled between 11/24/08 and 4/12/12. 1 patient withdrew consent prior to receiving any protocol therapy. 17 patients had a PS of 1. The majority of patients were stage IV. One DLT was noted out of 7 patients at dose level (DL) 1. Subsequently no DLTs were noted in 3 patients each enrolled at DL2-4 or 11 patients in the expansion cohort. The majority of grade 3 toxicities were hematologic with 1 grade 5 bowel perforation in dose level 1 in cycle 4. Best response in 24 evaluable patients: PR (8), stable (15), PD 1. Median survival for the entire group was 9.1 months.

CONCLUSION

This phase I study combining low-dose ultra-fractionated RT as a sensitizer to full dose G plus E was well tolerated with encouraging efficacy. This represents a novel strategy worthy of further investigation in advanced pancreatic cancer patients.

Exploiting sensitization windows of opportunity in hyper and hypo-fractionated radiation therapy

In contrast to the conventional radiotherapy/chemoradiotherapy paradigms used in the treatment of majority of cancer types, this review will describe two areas of radiobiology, hyperfractionated and hypofractionated radiation therapy, for cancer treatment focusing on application of novel concepts underlying these treatment modalities. The initial part of the review discusses the phenomenon of hyper-radiation sensitivity (HRS) at lower doses (0.1 to 0.6 Gy), describing the underlying mechanisms and how this could enhance the effects of chemotherapy, particularly, in hyperfractionated settings. The second part examines the radiobiological/physiological mechanisms underlying the effects of high-dose hypofractionated radiation therapy that can be exploited for tumor cure. These include abscopal/bystander effects, activation of immune system, endothelial cell death and effect of hypoxia with re-oxygenation. These biological properties along with targeted dose delivery and distribution to reduce normal tissue toxicity may make high-dose hypofractionation more effective than conventional radiation therapy for treatment of advanced cancers. The novel radiation physics based methods that take into consideration the tumor volume to be irradiated and normal tissue avoidance/tolerance can further improve treatment outcome and post-treatment quality of life. In conclusion, there is enough evidence to further explore novel avenues to exploit biological mechanisms from hyper-fractionation by enhancing the efficacy of chemotherapy and hypo-fractionated radiation therapy that could enhance tumor control and use imaging and technological advances to reduce toxicity.

FOLFIRI-bevacizumab and concurrent low-dose radiotherapy in metastatic colorectal cancer: preliminary results of a phase I-II study

BACKGROUND

To evaluate the effectiveness of low-dose radiation therapy (LDRT) and FOLFIRI-bevacizumab (FOLFIRI-B) combination in metastatic colorectal cancer.

METHODS

The primary objective of the study is to raise the clinical complete response (CR) rate from 5% to 25%. Secondary objectives include toxicity and progression-free survival. Patients underwent 12 FOLFIRI-B cycles plus two daily LDRT (20 cGy/6-hour interval) on the first and second days of each cycle.

RESULTS

CR and toxicity of 10 patients are reported. Considering irradiated sites, 10/10 patients had clinical partial response (PR) (7/10) or CR (3/10). Three clinical PR patients subsequently underwent surgery and reported a pathological CR in the irradiated sites. Grade 3-4 toxicities rate was 30%. With a median follow-up of 29 months (range: 12-49 months), 2/10 progression of disease in irradiated sites and 3/5 in non-irradiated sites were observed.

CONCLUSIONS

The very high response rate requires urgent verification in a larger patient series.

Low-dose fractionated radiotherapy and concomitant chemotherapy for recurrent or progressive glioblastoma: final report of a pilot study

BACKGROUND

Evaluated in this study were the feasibility and the efficacy of concurrent low dose fractionated radiotherapy (LD-FRT) and chemotherapy as palliative treatment for recurrent/progressive glioblastoma multiforme (GBM).

PATIENTS AND METHODS

Eligible patients had recurrent or progressive GBM, Karnofsky performance status ≥ 70, prior surgery, and standard radiochemotherapy treatment. Recurrence/progression disease during temozolomide (TMZ) received cisplatin (CDDP; 30 mg/m(2) on days 1, 8, 15), fotemustine (FTM; 40 mg/m(2) on days 2, 9, 16), and concurrent LD-FRT (0.3 Gy twice daily); recurrence/progression after 4 months from the end of adjuvant TMZ were treated by TMZ (150/200 mg/m(2) on days 1-5) concomitant with LD-FRT (0.4 Gy twice daily). Primary endpoints were safety and toxicity.

RESULTS

A total of 32 patients were enrolled. Hematologic toxicity G1-2 was observed in 18.7 % of patients and G3-4 in 9.4 %. One patient (3.1 %) had complete response, 3 (9.4 %) had partial response, 8 (25 %) had stable disease for at least 8 weeks, while 20 patients (62.5 %) experienced progressive disease. The clinical benefit was 37.5 %. Median progression-free survival (PFS) and overall survival (OS) were 5 and 8 months, respectively. Survival rate at 12 months was of 27.8 %.

CONCLUSION

LD-FRT and chemotherapy for recurrent/progressive GBM have a good toxicity profile and clinical outcomes, even though further investigation of this novel palliative treatment approach is warranted.

mRNA Expression Profiles for Prostate Cancer following Fractionated Irradiation Are Influenced by p53 Status

We assessed changes in cell lines of varying p53 status after various fractionation regimens to determine if p53 influences gene expression and if multifractionated (MF) irradiation can induce molecular pathway changes. LNCaP (p53 wild-type), PC3 (p53 null), and DU145 (p53 mutant) prostate carcinoma cells received 5 and 10 Gy as single-dose (SD) or MF (0.5 Gy x 10, 1 Gy x 10, and 2 Gy x 5) irradiation to simulate hypofractionated and conventionally fractionated prostate radiotherapies, respectively. mRNA analysis revealed 978 LNCaP genes differentially expressed (greater than two-fold change, P < .05) after irradiation. Most were altered with SD (69%) and downregulated (75%). Fewer PC3 (343) and DU145 (116) genes were induced, with most upregulated (87%, 89%) and altered with MF irradiation. Gene ontology revealed immune response and interferon genes most prominently expressed after irradiation in PC3 and DU145. Cell cycle regulatory (P = 9.23 x 10(-73), 14.2% of altered genes, nearly universally downregulated) and DNA replication/repair (P = 6.86 x 10(-30)) genes were most prominent in LNCaP. Stress response and proliferation genes were altered in all cell lines. p53-activated genes were only induced in LNCaP. Differences in gene expression exist between cell lines and after varying irradiation regimens that are p53 dependent. As the duration of changes is ≥24 hours, it may be possible to use radiation-inducible targeted therapy to enhance the efficacy of molecular targeted agents.

Low-dose fractionated radiotherapy and concomitant chemotherapy in glioblastoma multiforme with poor prognosis: a feasibility study

We explored the feasibility of concurrent palliative chemotherapy and low-dose fractionated radiotherapy (LD-FRT) in glioblastoma multiforme (GBM). Patients with recurrent/progressive GBM at least 3 months after the end of primary radiotherapy received 0.3 Gy twice daily with cisplatin and fotemustine if progressing on temozolomide, or 0.4 Gy twice daily with temozolomide if recurrent 4-6 months later (retreatment group). Newly diagnosed GBM with gross residual mass received 30 Gy with concomitant and adjuvant temozolomide and 0.4 Gy twice daily from the second adjuvant cycle (naive group) for 2-4 cycles. Twenty-six patients were enrolled. In the retreatment group (n = 17; median LD-FRT total dose 7.2 Gy [range 2.4-11.6]), grade 3 or 4 hematological toxicity was observed in 5.9% of patients. Median follow-up time was 20 months (range 4-35). Median progression-free survival (PFS) and overall survival (OS) from the time of recurrence or progression were 4 and 8 months, respectively (OS at 6 months, 69%; at 12 months, 16.7%). In the naive group (n = 9; median LD-FRT total dose 8 Gy [range 3.2-16]), grade 3 or 4 hematological toxicity was observed in 11.1% of patients. Median follow-up time was 17 months (range 8-20)-median PFS was 9 months, with PFS at 6 months and at 1 year of 66.7% and 26.7%, respectively; and median OS was 12 months, with OS at 6 months and at 1 year of 77.8% and 34.6%, respectively. LD-FRT with concurrent chemotherapy was well tolerated.

A systematic methodology review of phase I radiation dose escalation trials

BACKGROUND AND PURPOSE

The purpose of this review is to evaluate the methodology used in published phase I radiotherapy (RT) dose escalation trials. A specific emphasis was placed on the frequency of reporting late complications as endpoint.

MATERIALS AND METHODS

We performed a systematic literature review using a predefined search strategy to identify all phase I trials reporting on external radiotherapy dose escalation in cancer patients.

RESULTS

Fifty-three trials (phase I: n = 36, phase I-II: n = 17) fulfilled the inclusion criteria. Of these, 20 used a modified Fibonacci design for the RT dose escalation, but 32 did not specify a design. Late toxicity was variously defined as > 3 months (n = 43) or > 6 months (n = 3) after RT, or not defined (n = 7). In only nine studies the maximum tolerated dose (MTD) was related to late toxicity, while only half the studies reported the minimum follow-up period for dose escalation (n = 26).

CONCLUSION

In phase I RT trials, late complications are often not taken into account and there is currently no consensus on the methodology used for radiation dose escalation studies. We therefore propose a decision-tree algorithm which depends on the endpoint selected and whether a validated early surrogate endpoint is available, in order to choose the most appropriate study design.

The effect of docetaxel (taxotere) on human gastric cancer cells exhibiting low-dose radiation hypersensitivity

Low-dose radiation hypersensitivity (HRS) describes a phenomenon of excessive sensitivity to X ray doses <0.5 Gy. Docetaxel is a taxane shown to arrest cells in the G₂/M phase of the cell cycle. Some previous studies suggested that HRS might result from the abrogation of the early G₂ checkpoint arrest. First we tested whether HRS occurs in gastric cancer—derived cells, and whether pre-treatment of cells with low docetaxel concentrations can enhance the magnitude of HRS in gastric cancer cells. The results demonstrated HRS at ~0.3 Gy and the synergy between 0.3 Gy and docetaxel (3 nM for 24 h), and the additivity of other drug/dose combinations. The synergistic effect was associated with a significant docetaxel-induced G₂ accumulation. Next, we evaluated in time-course experiments ATM kinase activity and proteins associated with the induction and maintenance of the early G₂ checkpoint. The results of multi-immunoblot analysis demonstrate that HRS does not correlate with the ATM-dependent early G₂ checkpoint arrest. We speculate that G₂ checkpoint adaptation, a phenomenon associated with a prolonged cell cycle arrest, might be involved in HRS. Our results also suggest a new approach for the improvement the effectiveness of docetaxel-based radiotherapy using low doses per fraction.