Advances of stereotactic body radiotherapy in pancreatic cancer

An efficient rectangular optimization method for sparse orthogonal collimator based small animal irradiation

Objective.Intensity-modulated radiotherapy (IMRT) is widely used in clinical radiotherapy, treating varying malignancies with conformal doses. As the test field for clinical translation, preclinical small animal experiments need to mimic the human radiotherapy condition, including IMRT. However, small animal IMRT is a systematic challenge due to the lack of corresponding hardware and software for miniaturized targets.Approach.The sparse orthogonal collimators (SOC) based on the direct rectangular aperture optimization (RAO) substantially simplified the hardware for miniaturization. This study investigates and evaluates a significantly improved RAO algorithm for complex mouse irradiation using SOC. Because the Kronecker product representation of the rectangular aperture is the main limitation of the computational performance, we reformulated matrix multiplication in the data fidelity term using multiplication with small matrices instead of the Kronecker product of the dose loading matrices. Solving the optimization problem was further accelerated using the Fast Iterative Shrinkage-Thresholding Algorithm (FISTA).Main results.Four mouse cases, including a liver, a brain tumor, a concave U-target, and a complex total marrow irradiation (TMI) case, were included in this study with manually delineated targets and OARs. Seven coplanar-field SOC IMRT (sIMRT) plans were compared with idealistic fluence map based IMRT (iIMRT) plans. For the first three cases with simpler and smaller targets, the differences between sIMRT plans and iIMRT plans in the planning target volumes (PTV) statistics are within 1%. For the TMI case, the sIMRT plans are superior in reducing hot spots (also termedDmax) of PTV, kidneys, lungs, heart, and bowel by 20.5%, 31.5%, 24.67%, 20.13%, and 17.78%, respectively. On average, in four cases in this study, the sIMRT plan conformity is comparable to that of the iIMRT's with lightly increased R50 and Integral Dose by 2.23% and 2.78%.Significance.The significantly improved sIMRT optimization method allows fast plan creation in under 1 min for smaller targets and makes complex TMI planning feasible while achieving comparable dosimetry to idealistic IMRT with fluence map optimization.

Neuroendocrine Carcinoma of Uterine Cervix: Stereotactic Radiotherapy for Brain Metastasis and Stereotactic Body Radiotherapy for Renal and Pancreatic Metastases

A case of cervical neuroendocrine carcinoma (NEC) of the uterine cervix (NECUC) was presented. After total hysterectomy with bilateral salpingo-oophorectomy and adjuvant chemotherapy, a left renal tumor and a pancreatic lesion developed and were both diagnosed on pathological examination as metastases from NEC. In addition, a brainstem metastasis causing neurologic signs developed. The brain lesion was treated by stereotactic radiotherapy (SRT) and the renal and pancreatic lesions by stereotactic body radiotherapy (SBRT). Despite control of the renal and pancreatic lesions, multiple small lung metastases developed later. Recurrence and newly developed brain metastases were treated by repeat stereotactic radiosurgery (SRS)/SRT successfully. Chemotherapy was continued and controlled the lung metastases until three and a half years after the initial operation of the uterus.

Shear Wave Elastography Can Differentiate between Radiation-Responsive and Non-responsive Pancreatic Tumors: An ex Vivo Study with Murine Models

Neither contrast-enhanced computed tomography nor magnetic resonance imaging can monitor changes in the pancreatic ductal adenocarcinoma microenvironment during therapy. We hypothesized that shear wave elastography could overcome this limitation. To test this hypothesis, we measured the shear modulus of two groups of murine pancreatic tumors (KCKO, n = 30; PAN02, n = 30) treated with stereotactic body radiation therapy (SBRT). The mean shear modulus of KCKO tumors was 7.651 kPa higher than that of PAN02 tumors (p < 0.001). SBRT reduced the shear modulus in KCKO tumors by 8.914 kPa (p < 0.001). No significant difference in the shear modulus of SBRT-treated PAN02 tumors was observed. Additionally, necrotic and collagen densities were reduced only in the SBRT-treated KCKO tumors. Shear modulus was dependent on collagen distribution and histological texture parameters (i.e., entropy and fractional dimension). Shear wave elastography imaging differentiates between SBRT-responsive (KCKO) and non-responsive (PAN02) tumors.

A sparse orthogonal collimator for small animal intensity-modulated radiation therapy. Part II: hardware development and commissioning

PURPOSE

A dose-modulation device for small animal radiotherapy is required to use clinically analogous treatment techniques, which will likely increase the translatability of preclinical research results. Because the clinically used multileaf collimator (MLC) is impractical for miniaturization, we have developed a simpler, better-suited sparse orthogonal collimator (SOC) for delivering small animal intensity-modulated radiation therapy (IMRT) using a rectangular aperture optimization (RAO) treatment planning system.

METHODS

The SOC system was modeled in computer-aided design software and fabricated with machined tungsten leaves and three-dimensional (3D) printed leaf housing. A graphical user interface was developed for controlling and calibrating the SOC leaves, which are driven by Arduino-controlled stepper motors. A Winston-Lutz test was performed to assess mechanical alignment, and abutting field and grid dose patterns were created to analyze intra- and intercalibration leaf positioning error. Leaf transmission and penumbra were measured over the full range of gantry angles and leaf positions, respectively. Three SOC test plans were delivered, and film measurements were compared to the intended dose distributions. The differences in maximum, mean, and minimum, as well as pixelwise absolute dose differences, were compared for each structure, and a gamma analysis was performed for the target structures using criteria of 4% dose difference and 0.3 mm distance to agreement.

RESULTS

The Winston-Lutz test revealed maximum directional offsets between the SOC and primary collimator axes of 0.53 mm at 0° and 0.68 mm over the full 360°. Upper and lower abutting field patterns had maximum dose deviations of 18.8 ± 3.1% and 15.5 ± 2.9%, respectively, and grid patterns showed intra- and intercalibration repeatability of 93% and 91%, respectively. Extremely low midleaf (0.15 ± 0.05%) and interleaf (0.27 ± 0.22%) transmission was measured, with no significant rotational variation. The average penumbra was ~0.8 mm for all leaves at field center, with a range of 0.17 mm for all leaf positions. A highly concave test plan was delivered with a ~ 95% gamma analysis pass rate, and a realistic mouse phantom liver irradiation plan achieved a pass rate of ~98%. A highly complex dose distribution was also created with 551 SOC apertures averaging 2.4 mm in size.

CONCLUSIONS

A sparse orthogonal collimator was developed and commissioned, with promising preliminary dosimetry results. The SOC design, with its limited moving components and high dose-modulation resolution, is ideal for delivering high-quality small animal IMRT with our RAO-based treatment planning system.

The role of imaging in the clinical practice of radiation oncology for pancreatic cancer

Advances in technology have enabled the delivery of high doses of radiation therapy for pancreatic ductal adenocarcinoma (PDAC) with low rates of toxicity. Although the role of radiation for pancreatic cancer continues to evolve, encouraging results with newer techniques indicate that radiation may benefit selected patient populations. Imaging has been central to the modern successes of radiation therapy for PDAC. Here, we review the role of diagnostic imaging, imaging-based planning, and image guidance in radiation oncology practice for PDAC.

The efficacy of a new high intensity focused ultrasound therapy for locally advanced pancreatic cancer

PURPOSE

To compare the survival benefit and safety of the low power cumulative and traditional high intensity focused ultrasound (HIFU) for locally advanced pancreatic cancer.

METHOD

We retrospectively analyzed 38 patients with locally advanced, inoperable, stage III pancreatic patients received HIFU treatment between January 2008 and April 2014 in the Department of Surgery, the Second Affiliated Hospital, Zhejiang University, School of Medicine. 11 of them received the low power cumulative HIFU treatment, while other 27 received the traditional HIFU treatment. The HIFU device used was the FEP-BY02 (Yuande Biomedical Engineering Co. Ltd, Beijing, China). Serum biochemistry and adverse events were assessed before and after treatment. All the patients were followed up until death. The survival rate and adverse events of two groups were compared.

RESULTS

In 38 patients, the baseline characteristics including gender, age, Karnofsky performance status (KPS) score, tumor location of two groups were generally well balanced (P > 0.05). The median overall survival (OS) for low power cumulative HIFU group was 10.3 months (95% CI, 6.3-14.3 months), which is significantly longer than traditional HIFU group with 6.0 months (95% CI, 5.2-6.8 months) (P = 0.018). In low power cumulative HIFU group, the 6-month and 12-month survival rates were higher than traditional group, 100% v.s 44.4%, 11.1% v.s 36.4%, respectively. The adverse events in both groups include abdominal pain, fever, C-reactive protein (CRP) elevated. The incidence was lower in low power cumulative HIFU group, however, without statistical significance.

CONCLUSION

The low power cumulative HIFU treatment showed a statistical significance in survival benefit with better safety profile compared to the traditional HIFU treatment in patients with locally advanced pancreatic cancer.

Stereotactic body radiotherapy for renal cell cancer and pancreatic cancer : Literature review and practice recommendations of the DEGRO Working Group on Stereotactic Radiotherapy

PURPOSE

This report of the Working Group on Stereotactic Radiotherapy of the German Society of Radiation Oncology (DEGRO) aims to provide a literature review and practice recommendations for stereotactic body radiotherapy (SBRT) of primary renal cell cancer and primary pancreatic cancer.

METHODS

A literature search on SBRT for both renal cancer and pancreatic cancer was performed with focus on prospective trials and technical aspects for clinical implementation.

RESULTS

Data on renal and pancreatic SBRT are limited, but show promising rates of local control for both treatment sites. For pancreatic cancer, fractionated SBRT should be preferred to single-dose treatment to reduce the risk of gastrointestinal toxicity. Motion-compensation strategies and image guidance are paramount for safe SBRT delivery in both tumor entities.

CONCLUSION

SBRT for renal cancer and pancreatic cancer have been successfully evaluated in phase I and phase II trials. Pancreatic SBRT should be practiced carefully and only within prospective protocols due to the risk of severe gastrointestinal toxicity. SBRT for primary renal cell cancer appears a viable option for medically inoperable patients but future research needs to better define patient selection criteria and the detailed practice of SBRT.

Stereotactic body radiation therapy for patients with recurrent pancreatic adenocarcinoma at the abdominal lymph nodes or postoperative stump including pancreatic stump and other stump

Background and aim

The aim of this study is to evaluate the efficacy and safety of stereotactic body radiation therapy (SBRT) using CyberKnife in the treatment of patients with recurrent pancreatic adenocarcinoma at the abdominal lymph node or stump after surgery.

Patients and methods

Between October 1, 2006 and May 1, 2015, patients with recurrent pancreatic adenocarcinoma at the abdominal lymph node or stump after surgery were enrolled and treated with SBRT at our hospital. The primary end point was local control rate after SBRT. Secondary end points were overall survival, time to symptom alleviation, and toxicity, assessed using the Common Terminology Criteria for Adverse Events version 4.0.

Results

Twenty-four patients with 24 lesions (17 abdominal lymph nodes and seven stumps) were treated with SBRT, of which five patients presented with abdominal lymph nodes and synchronous metastases in the liver and lung. The 6-, 12-, and 24-month actuarial local control rates were 95.2%, 83.8%, and 62.1%, respectively. For the entire cohort, the median overall survival from diagnosis and SBRT was 28.9 and 12.2 months, respectively. Symptom alleviation was observed in eleven of 14 patients (78.6%) within a median of 8 days (range, 1–14 days) after SBRT. Nine patients (37.5%) experienced Common Terminology Criteria for Adverse Events version 4.0 grade 1–2 acute toxicities; one patient experienced grade 3 acute toxicity due to thrombocytopenia.

Conclusion

SBRT is a safe and effective treatment for patients with recurrent pancreatic adenocarcinoma at the abdominal lymph node or stump after surgery. Further studies are needed before SBRT can be recommended routinely.

Current situation and predicament of multidisciplinary treatment of pancreatic cancer

Pancreatic adenocarcinoma is one of the deadliest solid malignancies. As the anatomy position of the pancreas is deep, most patients are difficult to diagnose in the early stage. Approximately 40% of patients are diagnosed with locally advanced or metastatic disease at the time of diagnosis, which severely limits the number of patients who can undergo surgical resection. There is an urgent need to explore new treatments or comprehensive treatment for pancreatic cancer, in order to improve the long-term survival rate and quality of life. Recent therapeutic advances for advanced pancreatic cancer have improved overall survival, but the prognosis remains grim. This article reviews both the major therapeutic strategies and their predicaments for pancreatic adenocarcinoma, including currently ongoing clinical trials about use of the new agents and technologies.