Modeling Combined Chemotherapy and Particle Therapy for Locally Advanced Pancreatic Cancer

Analysis of the cost-effectiveness of proton beam therapy for unresectable pancreatic cancer in Japan

BACKGROUND

Proton beam therapy (PBT) has recently been included in Japan's social health insurance benefits package. This study aimed to determine the cost-effectiveness of PBT for unresectable, locally advanced pancreatic cancer (LAPC) as a replacement for conventional photon radiotherapy (RT).

METHODS

We estimated the incremental cost-effectiveness ratio (ICER) of PBT as a replacement for three-dimensional conformal RT (3DCRT), a conventional photon RT, using clinical evidence in the literature and expense complemented by expert opinions. We used a decision tree and an economic and Markov model to illustrate the disease courses followed by LAPC patients. Effectiveness was estimated as quality-adjusted life years (QALY) using utility weights for the health state. Social insurance fees were calculated as the costs. The stability of the ICER against the assumptions made was appraised using sensitivity analyses.

RESULTS

The effectiveness of PBT and 3DCRT was 1.67610615 and 0.97181271 QALY, respectively. The ICER was estimated to be ¥5,376,915 (US$46,756) per QALY. According to the suggested threshold for anti-cancer therapy from the Japanese authority of ¥7,500,000 (US$65,217) per QALY gain, such a replacement would be considered cost-effective. The one-way and probabilistic sensitivity analyses demonstrated stability of the base-case ICER.

CONCLUSION

PBT, as a replacement for conventional photon radiotherapy, is cost-effective and justifiable as an efficient use of finite healthcare resources. Making it a standard treatment option and available to every patient in Japan is socially acceptable from the perspective of health economics.

Carbon Ions for Hypoxic Tumors: Are We Making the Most of Them?

Hypoxia, which is associated with abnormal vessel growth, is a characteristic feature of many solid tumors that increases their metastatic potential and resistance to radiotherapy. Carbon-ion radiation therapy, either alone or in combination with other treatments, is one of the most promising treatments for hypoxic tumors because the oxygen enhancement ratio decreases with increasing particle LET. Nevertheless, current clinical practice does not yet fully benefit from the use of carbon ions to tackle hypoxia. Here, we provide an overview of the existing experimental and clinical evidence supporting the efficacy of C-ion radiotherapy in overcoming hypoxia-induced radioresistance, followed by a discussion of the strategies proposed to enhance it, including different approaches to maximize LET in the tumors.

Radiosensitization of NSCLC cells to X-rays and carbon ions by the CHK1/CHK2 inhibitor AZD7762, Honokiol and Tunicamycin

Although radiotherapy, especially carbon-ion radiotherapy, is an effective treatment modality against non-small-cell lung cancer (NSCLC), studies using radiation combined with sensitizer for improving the efficacy of radiotherapy are still needed. In this work, we aimed to investigate in NSCLC A549 and H1299 cell lines the effects of different linear energy transfer (LET) radiations combined with diverse sensitizing compounds. Cells pretreated with the CHK1/CHK2 inhibitor AZD7762, Honokiol or Tunicamycin were irradiated with low-LET X-rays and high-LET carbon ions. Cell survival was assessed using the clonogenic cell survival assay. Cell cycle distribution and apoptosis were measured with flow cytometry, and DNA double strand break (DSB) and repair were detected using γ-H2AX immunofluorescence staining. Our results revealed that AZD7762, Honokiol and Tunicamycin demonstrated low cytotoxicity to NSCLC cells and a pronounced radiosensitizing effect on NSCLC cells exposed to carbon ions than X-rays. Unrepaired DNA DSB damages, the abrogation of G2/M arrest induced by irradiation, and finally apoptotic cell death were the main causes of the radiosensitizing effect. Thus, our data suggest that high-LET carbon ion combined with these compounds may be a potentially effective therapeutic strategy for locally advanced NSCLC.

Carbon Ion Radiobiology

Simple Summary

Radiotherapy with carbon ions has been used for over 20 years in Asia and Europe and is now planned in the USA. The physics advantages of carbon ions compared to X-rays are similar to those of protons, but their radiobiological features are quite distinct and may lead to a breakthrough in the treatment of some cancers characterized by high mortality.

Abstract

Radiotherapy using accelerated charged particles is rapidly growing worldwide. About 85% of the cancer patients receiving particle therapy are irradiated with protons, which have physical advantages compared to X-rays but a similar biological response. In addition to the ballistic advantages, heavy ions present specific radiobiological features that can make them attractive for treating radioresistant, hypoxic tumors. An ideal heavy ion should have lower toxicity in the entrance channel (normal tissue) and be exquisitely effective in the target region (tumor). Carbon ions have been chosen because they represent the best combination in this direction. Normal tissue toxicities and second cancer risk are similar to those observed in conventional radiotherapy. In the target region, they have increased relative biological effectiveness and a reduced oxygen enhancement ratio compared to X-rays. Some radiobiological properties of densely ionizing carbon ions are so distinct from X-rays and protons that they can be considered as a different “drug” in oncology, and may elicit favorable responses such as an increased immune response and reduced angiogenesis and metastatic potential. The radiobiological properties of carbon ions should guide patient selection and treatment protocols to achieve optimal clinical results.

Novel strategies using modern radiotherapy to improve pancreatic cancer outcomes: toward a new standard?

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most aggressive solid tumours with an estimated 5-year overall survival rate of 7% for all stages combined. In this highly resistant disease that is located in the vicinity of many radiosensitive organs, the role of radiotherapy (RT) and indications for its use in this setting have been debated for a long time and are still under investigation. Although a survival benefit has yet to be clearly demonstrated for RT, it is the only technique, other than surgery, that has been demonstrated to lead to local control improvement. The adjuvant approach is now strongly challenged by neoadjuvant treatments that could spare patients with rapidly progressive systemic disease from unnecessary surgery and may increase free margin (R0) resection rates for those eligible for surgery. Recently developed dose-escalated RT treatments, designed either to maintain full-dose chemotherapy or to deliver a high biologically effective dose, particularly to areas of contact between the tumour and blood vessels, such as hypofractionated ablative RT (HFA-RT) or stereotactic body RT (SBRT), are progressively changing the treatment landscape. These modern strategies are currently being tested in prospective clinical trials with encouraging preliminary results, paving the way for more effective treatment combinations using novel targeted therapies. This review summarizes the current literature regarding the use of RT for the treatment of primary PDAC, describes the limitations of conventional RT, and discusses the emerging role of dose-escalated RT and heavy-particle RT.

Evaluating dosimetric constraints for carbon ion radiotherapy in the treatment of locally advanced pancreatic cancer

OBJECTIVE

To identify a safe carbon ion radiotherapy (CIRT) regimen for patients with locally advanced pancreatic cancer (LAPC).

METHODS

We generated treatment plans for 13 consecutive, unselected patients who were treated for LAPC with CIRT at our center using three dose and fractionation schedules: 4.6 GyRBE × 12, 4.0 GyRBE × 14, and 3.0 GyRBE × 17. We tested the ability to meet published dose constraints for the duodenum, stomach, and small bowel as a function of dose schedule and distance between the tumor and organs at risk.

RESULTS

Using 4.6 GyRBE × 12 and 4.0 GyRBE × 14, critical (high-dose) constraints could only reliably be achieved when target volumes were not immediately adjacent to organs at risk. Critical constraints could be met in all cases using 3.0 GyRBE × 17. Low-dose constraints could not uniformly be achieved using any dose schedule.

CONCLUSION

While selected patients with LAPC may be treated safely with a CIRT regimen of 4.6 GyRBE × 12, our dosimetric analyses indicate that a more conservative schedule of 3.0 GyRBE × 17 may be required to safely treat a broader population of LAPC patients, including those with large tumors and tumors that approach gastrointestinal organs at risk. The result of this work was used to guide an ongoing clinical trial.

Beam direction arrangement using a superconducting rotating gantry in carbon ion treatment for pancreatic cancer

OBJECTIVES

Carbon ion radiotherapy provides a concentrated dose distribution to the target and has several advantages over photon radiotherapy. This study aimed to evaluate the optimal beam direction in carbon ion pencil beam scanning and compare dose distributions between the rotating gantry system (RGS) and fixed-beam port system (FBPS).

METHODS

Patients with locally advanced pancreatic cancer were randomly selected. First, dose-volume parameters of 7-beam directions in the prone position were evaluated. Second, a composite plan developed using 4-beam directions in RGS was compared with that developed using FBPS, with a total prescribed dose of 55.2 Gy (relative biological effectiveness, RBE) in 12 fractions.

RESULTS

Target coverages in the composite plan did not widely differ. For the first and second segments of the duodenum, the mean dose of D2cc was not significantly changed (23.80 ± 11.90 Gy [RBE] and 25.63 ± 10.41 Gy [RBE] for RGS and FBPS, respectively). However, the dose-volume histogram curve in RGS showed a prominent dose reduction in the low-dose region. No significant differences were observed in the stomach, third and fourth segments of the duodenum, and spinal cord. The mean dose of the total kidney was similar between RGS and FBPS.

CONCLUSIONS

Compared with that of FBPS, the 4-beam arrangement in the prone position using RGS provides comparable or superior dose distribution in the surrounding normal organ while achieving the same target coverage. In addition, RGS allows for single-patient positioning.

ADVANCES IN KNOWLEDGE

RGS is beneficial in delivering radiotherapy doses to the duodenum and allows for single-patient positioning and a simple planning process.

4DMRI-based investigation on the interplay effect for pencil beam scanning proton therapy of pancreatic cancer patients

BACKGROUND

Time-resolved volumetric magnetic resonance imaging (4DMRI) offers the potential to analyze 3D motion with high soft-tissue contrast without additional imaging dose. We use 4DMRI to investigate the interplay effect for pencil beam scanning (PBS) proton therapy of pancreatic cancer and to quantify the dependency of residual interplay effects on the number of treatment fractions.

METHODS

Based on repeated 4DMRI datasets for nine pancreatic cancer patients, synthetic 4DCTs were generated by warping static 3DCTs with 4DMRI deformation vector fields. 4D dose calculations for scanned proton therapy were performed to quantify the interplay effect by CTV coverage (v95) and dose homogeneity (d5/d95) for incrementally up to 28 fractions. The interplay effect was further correlated to CTV motion characteristics. For quality assurance, volume and mass conservation were evaluated by Jacobian determinants and volume-density comparisons.

RESULTS

For the underlying patient cohort with CTV motion amplitudes < 15 mm, we observed significant correlations between CTV motion amplitudes and both the length of breathing cycles and the interplay effect. For individual fractions, tumor underdosage down to v95 = 70% was observed with pronounced dose heterogeneity (d5/d95 = 1.3). For full × 28 fractionated treatments, we observed a mitigation of the interplay effect with increasing fraction numbers. On average, after seven fractions, a CTV coverage with 95-107% of the prescribed dose was reached with sufficient dose homogeneity. For organs at risk, no significant differences were found between the static and accumulated dose plans for 28 fractions.

CONCLUSION

Intrafractional organ motion exhibits a large interplay effect for PBS proton therapy of pancreatic cancer. The interplay effect correlates with CTV motion, but can be mitigated efficiently by fractionation, mainly due to different breathing starting phases in fractionated treatments. For hypofractionated treatments, a further restriction of motion may be required. Repeated 4DMRI measurements are a viable tool for pre- and post-treatment evaluations of the interplay effect.

4D dose calculation for pencil beam scanning proton therapy of pancreatic cancer using repeated 4DMRI datasets

4D magnetic resonance imaging (4DMRI) has a high potential for pancreatic cancer treatments using proton therapy, by providing time-resolved volumetric images with a high soft-tissue contrast without exposing the patient to any additional imaging dose. In this study, we aim to show the feasibility of 4D treatment planning for pencil beam scanning (PBS) proton therapy of pancreatic cancer, based on five repeated 4DMRI datasets and 4D dose calculations (4DDC) for one pancreatic cancer patient. To investigate the dosimetric impacts of organ motion, deformation vector fields were extracted from 4DMRI, which were then used to warp a static CT of the patient, so as to generate synthetic 4DCT (4DCT-MRI). CTV motion amplitudes  <15 mm were observed for this patient. The results from 4DDC show pronounced interplay effects in the CTV with dose homogeneity d5/d95 and dose coverage v95 being 1.14 and 91%, respectively, after a single fraction of the treatment. An averaging effect was further observed when increasing the number of fractions. Motion effects can become less dominant and dose homogeneity d5/d95  =  1.03 and dose coverage v95  =  [Formula: see text] within the CTV can be achieved after 28 fractions. The observed inter-fractional organ and tumor motion variations underline the importance of 4D imaging before and during PBS proton therapy.

Improved Survival in Patients with Resected Pancreatic Carcinoma Using Postoperative Intensity-Modulated Radiotherapy and Regional Intra-Arterial Infusion Chemotherapy

BACKGROUND We assessed the role of adjuvant intensity-modulated radiotherapy (IMRT) in combination with chemotherapy for pancreatic carcinomas after curative resection and identified prognostic factors related to pancreatic carcinoma after multidisciplinary treatment strategies. MATERIAL AND METHODS Pancreatic carcinoma patients (n=61) who received adjuvant radiotherapy after resection (median dose, 50.4 Gy) between 2010 and 2016 were retrospectively identified. Sixty patients received chemotherapy, including concurrent chemoradiotherapy (CCRT), systemic chemotherapy, and regional intra-arterial infusion chemotherapy (RIAC). The Kaplan-Meier method was used to measure the 3-year overall survival (OS) and disease-free survival (DFS) rates. Log-rank univariate analysis and multivariate Cox regression model analysis were used to identify prognostic factors. RESULTS Median follow-up time was 25.5 (range, 4.9-59.7) months. The 3-year OS and DFS rates were 31.0% and 16.1%, respectively. The median OS and DFS were 27.4 and 16.7 months, respectively. Multivariate analysis indicated that independent favorable predictors for OS were CCRT (p=0.039) and postoperative RIAC (p=0.044). Moreover, postoperative RIAC (p=0.027), and pre-radiotherapy CA19-9 ≤37 U/mL (p=0.0080) were independent favorable predictors for DFS. The combination of radiotherapy and chemotherapy was tolerated well by the patients, and no treatment-related death occurred. CONCLUSIONS Combined IMRT and adjuvant chemotherapy appeared safe and effective for pancreatic carcinoma. CCRT was associated with improved survival with acceptable toxicity. We propose that radiotherapy could be a part of postoperative treatment, but it should be administered concurrently with chemotherapy. Adding RIAC was associated with improved OS and DFS and it could be integrated into the postoperative treatment regimen.

Integration of Stereotactic Body Radiation Therapy into the Multidisciplinary Management of Pancreatic Cancer

Although most patients with pancreatic cancer die of metastatic disease, an autopsy study showed that up to one-third of patients die of predominantly local disease. This patient population stands to benefit the most from radiation, surgery, or both. Unfortunately, however, single-agent chemotherapy has had minimal benefit in pancreatic cancer, and most patients progress distantly before receiving radiation therapy (RT). With the addition of multiagent chemotherapy, patients are living longer, and RT has emerged as an important modality in preventing local progression. Standard chemoradiation delivered over 5-6 weeks has been shown to improve local control, but this approach delays full-dose systemic therapy and increases toxicity when compared to chemotherapy alone. Stereotactic body RT (SBRT) delivered in 3-5 fractions can be used to accurately target the pancreatic tumor with small margins and limited acute treatment-related toxicity. Given the favorable toxicity profile, SBRT can easily be integrated with other therapies in all stages of pancreatic cancer. However, future studies are necessary to determine optimal dose or fractionation regimens and sequencing with targeted therapies and immunotherapy. The purpose of this review is to discuss our current understanding of SBRT in the multidisciplinary management of patients with pancreatic cancer and future implications.

Nuclear physics in particle therapy: a review

Charged particle therapy has been largely driven and influenced by nuclear physics. The increase in energy deposition density along the ion path in the body allows reducing the dose to normal tissues during radiotherapy compared to photons. Clinical results of particle therapy support the physical rationale for this treatment, but the method remains controversial because of the high cost and of the lack of comparative clinical trials proving the benefit compared to x-rays. Research in applied nuclear physics, including nuclear interactions, dosimetry, image guidance, range verification, novel accelerators and beam delivery technologies, can significantly improve the clinical outcome in particle therapy. Measurements of fragmentation cross-sections, including those for the production of positron-emitting fragments, and attenuation curves are needed for tuning Monte Carlo codes, whose use in clinical environments is rapidly increasing thanks to fast calculation methods. Existing cross sections and codes are indeed not very accurate in the energy and target regions of interest for particle therapy. These measurements are especially urgent for new ions to be used in therapy, such as helium. Furthermore, nuclear physics hardware developments are frequently finding applications in ion therapy due to similar requirements concerning sensors and real-time data processing. In this review we will briefly describe the physics bases, and concentrate on the open issues.