Biologic mesh spacer placement facilitates safe delivery of dose-intense radiation therapy: A novel treatment option for unresectable liver tumors

Utilization of a stabilized hyaluronic acid spacer in SBRT for retroperitoneal cancers: A case series and dosimetric analysis

Objectives

To evaluate the clinical indications, post-operative complications, and dosimetric impact of stabilized hyaluronic acid (sHA) spacer insertion in the retroperitoneum for stereotactic body radiation therapy (SBRT) of retroperitoneal cancers.

Patients and methods

This retrospective study analyzed two cases of SBRT for retroperitoneal lesions: a primary left renal cell carcinoma and an oligometastatic renal cell carcinoma (RCC) lesion in the right adrenal gland. In both cases, a sHA spacer was percutaneously inserted between the bowel and the lesion. The spacer was placed under laparoscopic and ultrasound guidance for the renal tumor, and under CT guidance for the adrenal lesion. The prescribed dose was 42 Gy in three fractions for the primary renal lesion and 40 Gy in five fractions for the adrenal lesion. Dosimetric parameters were evaluated in two planning scenarios: (1) without the spacer, adhering to OAR constraints, and (2) with the spacer.

Results

Spacer insertion for the primary left renal cancer significantly improved PTV D95% from 67.9 % to 99.5 % of the prescribed dose, a 46.5 % increase. PTV D99% increased from 54.5 % to 86.7 %, reflecting a 59.1 % improvement. The large bowel's maximum dose was reduced from 28.2 Gy to 24.4 Gy, and the volume receiving 24 Gy was minimal with the spacer (0.06 cc). For the right oligometastatic adrenal lesion, despite a fourfold increase in tumor volume, post-spacer dosimetry showed improved PTV coverage without exceeding OAR constraints. No post-operative complications were observed in either case.

Conclusion

This is the first report on sHA spacer use in the retroperitoneum for SBRT. Spacer insertion near the large bowel significantly improves dosimetry, enabling higher doses to targets while keeping OAR doses within safe limits. Further research with a larger patient population is required to assess safety and for optimization of the technique for spacer placement in order to enhance clinical outcomes.

Laparoscopic spacer placement for bulky lymph node metastasis of cervical cancer: A case report

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Spacers focus high-dose radiotherapy towards the target lesion.

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Laparoscopic insertion of spacers allows for rapid initiation of radiotherapy.

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Spacers may be applied to patients requiring multidisciplinary treatment beyond standard therapy.

Intracranial Autograft Fat Placement to Separate the Optic Chiasm from Tumor to Improve Stereotactic Radiotherapy Dosimetry

BACKGROUND

Radiation therapy for intracranial lesions is constrained by dose to neurologic organs at risk.

CASE DESCRIPTION

We report 2 cases, a newly diagnosed chondrosarcoma and a previously irradiated meningioma, with tumors that abutted the optic chiasm following subtotal resection. Definitive radiotherapy would have required either undercoverage of the tumor or treatment of the chiasm with doses posing an unacceptable risk of blindness. Therefore, the patients underwent open surgery with placement of an abdominal fat autograft to provide space between the tumor and the optic structures at risk. Patients received definitive fractionated stereotactic radiotherapy. For each patient, we retrospectively compared the treated plan (with fat autograft) to a second plan generated using the pre-autograft imaging, maintaining similar tumor coverage. For the chondrosarcoma, the fat autograft reduced the optic chiasm maximum dose by 21% (70.4 Gy to 55.3 Gy). For the reirradiated peri-optic meningioma, the optic chiasm maximum dose was reduced by 10% (50.8 Gy to 45.9 Gy), the left optic nerve by 17% (48.9 Gy to 40.4 Gy), and the right optic nerve by 30% (32.3 Gy to 22.6 Gy).

CONCLUSIONS

We demonstrate the utility of abdominal fat autograft placement to maximize coverage of tumor while minimizing dose to intracranial organs at risk.

Adrenal SBRT: a multi-institutional review of treatment outcomes and toxicity

The adrenal glands are a common site of metastatic disease. Definitive treatment for oligometastatic disease using ablative radiotherapy is becoming common in modern radiation oncology practice. However, most data on the treatment of adrenal metastases are limited to single institution reports. Furthermore, delivering ablative radiotherapy doses to intra-abdominal lesions can be challenging due to the proximity of the gastrointestinal tract. We report the outcomes of a multi-institutional cohort of patients treated with definitive radiotherapy for adrenal metastases, primarily using 10 fraction regimens. Retrospective review of institutional databases revealed 29 lesions in 27 patients were treated from 2005 to 2018 at two institutions. Outcome data, including local control, disease-free, and overall survival were abstracted from the medical record system. Toxicity was graded using CTCAE v5.0. Detailed radiotherapy data was abstracted from the treatment planning systems. The median dose was 50 Gy in 10 fractions. Actuarial 1 and 2 year local control was 86% and 76% respectively. The median overall and disease-free survival were 22.8 and 5.6 months respectively. There were no associations identified between local failure and GTV and PTV physical or biologic effective dose. Two patients developed late Grade 3 gastrointestinal toxicity. High dose radiotherapy to adrenal metastases is a feasible treatment with excellent local control and a reasonable safety profile. For lesions in close proximity to gastrointestinal structures, moderately hypofractionated 10 fraction regimens may be a reasonable compromise between local control and toxicity.

In silico comparison of the dosimetric impacts of a greater omentum spacer for abdominal and pelvic tumors in carbon-ion, proton and photon radiotherapy

PURPOSE

The purpose of this study was to compare carbon-ion (C-ion), proton and photon radiotherapy (RT) plans with regard to dose reduction of the gastrointestinal (GI) tract by using a greater omentum spacer (GO spacer).

METHODS

We retrospectively retrieved data for ten patients who received the GO spacer as surgical spacer placement for abdominal and pelvic tumors. Simulation plans were created on pre-spacer Computed Tomography (CT) and post-spacer CT for C-ion RT, proton RT and photon RT to compare the dose of the GI tract. The plans were normalized so that at least 95% of the planning target volume (PTV) received 70 Gy (relative biological effectiveness equivalent) delivered in 35 fractions. All plans were created with the lowest possible dose to the GI tract under conditions that meet the dose constraints for the PTV and spinal cord (maximum dose < 45 Gy). The part of the GI tract to be evaluated was defined as that most adjacent to the PTV. C-ion RT plans and proton RT plans were calculated by a spot scanning technique, and photon RT plans were calculated employing by fixed-field intensity-modulated radiation therapy.

RESULTS

D2 cc and V10-70 of the GI tract were significantly lower on post-spacer plans than on pre-spacer plans for all three RT modalities. Regarding post-spacer plans, D2 cc of the GI tract was significantly lower on C-ion RT plans and proton RT plans than on photon RT plans (C-ion vs photon p = 0.001, proton vs photon p = 0.002). However, there was no significant difference between C-ion RT plans and proton RT plans for D2 cc of the GI tract (C-ion vs proton p = 0.992). In the photon RT plan for one patient, D2 cc of the GI tract did not meet < 50 Gy.

CONCLUSIONS

The GO spacer shows a significant dose reduction effect on the GI tract.

Non-Coding RNAs and Resistance to Anticancer Drugs in Gastrointestinal Tumors

Non-coding RNAs are important regulators of gene expression and transcription. It is well established that impaired non-coding RNA expression especially the one of long non-coding RNAs and microRNAs is involved in a number of pathological conditions including cancer. Non-coding RNAs are responsible for the development of resistance to anticancer treatments as they regulate drug resistance-related genes, affect intracellular drug concentrations, induce alternative signaling pathways, alter drug efficiency via blocking cell cycle regulation, and DNA damage response. Furthermore, they can prevent therapeutic-induced cell death and promote epithelial-mesenchymal transition (EMT) and elicit non-cell autonomous mechanisms of resistance. In this review, we summarize the role of non-coding RNAs for different mechanisms resulting in drug resistance (e.g., drug transport, drug metabolism, cell cycle regulation, regulation of apoptotic pathways, cancer stem cells, and EMT) in the context of gastrointestinal cancers.

The role of radioprotective spacers in clinical practice: a review

The delivery of high dose radiotherapy to tumors is often limited by the proximity of the surrounding radiosensitive normal tissues, even using modern techniques such as intensity modulated radiation therapy (IMRT). Previous studies have reported that placement of a spacer can effectively displace normal tissues. So that they are some distance away from the lesion, thus allowing for the safe delivery of high-dose radiation. The application of radioprotective spacers was first reported 30 years ago regarding radiotherapy of tongue and abdominal cancers; more recently, they are increasingly being used in prostate cancer. This review focuses on the published data concerning the features of different types of spacers and their application in various tumor sites. Placement-related complications and the cost-effectiveness of the spacers are also discussed. With the increasing use of high-precision radiotherapy in clinical practice, especially the paradigm-changing stereotactic body radiotherapy (SBRT), more robust studies are warranted to further establish the role of radioprotective spacers through materials development and novel placement techniques.

A Novel Absorbable Radiopaque Hydrogel Spacer to Separate the Head of the Pancreas and Duodenum in Radiation Therapy for Pancreatic Cancer

PURPOSE

We assessed the feasibility and theoretical dosimetric advantages of an injectable hydrogel to increase the space between the head of the pancreas (HOP) and duodenum in a human cadaveric model.

METHODS AND MATERIALS

Using 3 human cadaveric specimens, an absorbable radiopaque hydrogel was injected between the HOP and duodenum by way of open laparotomy in 1 case and endoscopic ultrasound (EUS) guidance in 2 cases. The cadavers were subsequently imaged using computed tomography and dissected for histologic confirmation of hydrogel placement. The duodenal dose reduction and planning target volume (PTV) coverage were characterized using pre- and postspacer injection stereotactic body radiation therapy (SBRT) plans for the 2 cadavers with EUS-guided placement, the delivery method that appeared the most clinically desirable. Modeling studies were performed using 60 SBRT plans consisting of 10 previously treated patients with unresectable pancreatic cancer, each with 6 different HOP-duodenum separation distances. The duodenal volume receiving 15 Gy (V15), 20 Gy (V20), and 33 Gy (V33) was assessed for each iteration.

RESULTS

In the 3 cadaveric studies, an average of 0.9 cm, 1.1 cm, and 0.9 cm HOP-duodenum separation was achieved. In the 2 EUS cases, the V20 decreased from 3.86 cm³ to 0.36 cm³ and 3.75 cm³ to 1.08 cm³ (treatment constraint <3 cm³), and the V15 decreased from 7.07 cm³ to 2.02 cm³ and 9.12 cm³ to 3.91 cm³ (treatment constraint <9 cm³). The PTV coverage improved or was comparable between the pre- and postinjection studies. Modeling studies demonstrated that a separation of 8 mm was sufficient to consistently reduce the V15, V20, and V33 to acceptable clinical constraints.

CONCLUSIONS

Currently, dose escalation has been limited owing to radiosensitive structures adjacent to the pancreas. We demonstrated the feasibility of hydrogel separation of the HOP and duodenum. Future studies will evaluate the safety and efficacy of this technique with the potential for more effective dose escalation using SBRT or intensity-modulated radiation therapy to improve the outcomes in patients with unresectable pancreatic cancer.