Stereotactic body radiotherapy in lung cancer: an update

Review on endobronchial therapies-current status and future

There is a growing demand for lung parenchymal-sparing localized therapies due to the rising incidence of multifocal lung cancers and the growing number of patients who cannot undergo surgery. Lung cancer screening has led to the discovery of more pre-malignant or early-stage lung cancers, and the focus has shifted from treatment to prevention. Transbronchial therapy is an important tool in the local treatment of lung cancers, with microwave ablation showing promise based on early and mid-term results. To improve the precision and efficiency of transbronchial ablation, adjuncts such as mobile C-arm platforms, software to correct for computed tomography (CT)-to-body divergence, metal-containing nanoparticles, and robotic bronchoscopy are useful. Other forms of energy such as steam vapor therapy, pulsed electric field, and photodynamic therapy are being intensively investigated. In addition, the future of transbronchial therapies may involve the intratumoral injection of novel agents such as immunomodulating agents, gene therapies, and chimeric antigen receptor T cells. Extensive pre-clinical and some clinical research has shown the synergistic abscopal effect of combination of these agents with ablation. This article aims to provide the latest updates on these technologies and explore their most likely future applications.

A high-resolution large-area detector for quality assurance in radiotherapy

Hadron therapy is an advanced radiation modality for treating cancer, which currently uses protons and carbon ions. Hadrons allow for a highly conformal dose distribution to the tumour, minimising the detrimental side-effects due to radiation received by healthy tissues. Treatment with hadrons requires sub-millimetre spatial resolution and high dosimetric accuracy. This paper discusses the design, fabrication and performance tests of a detector based on Gas Electron Multipliers (GEM) coupled to a matrix of thin-film transistors (TFT), with an active area of 60 × 80 mm2 and 200 ppi resolution. The experimental results show that this novel detector is able to detect low-energy (40 kVp X-rays), high-energy (6 MeV) photons used in conventional radiation therapy and protons and carbon ions of clinical energies used in hadron therapy. The GEM-TFT is a compact, fully scalable, radiation-hard detector that measures secondary electrons produced by the GEMs with sub-millimetre spatial resolution and a linear response for proton currents from 18 pA to 0.7 nA. Correcting known detector defects may aid in future studies on dose uniformity, LET dependence, and different gas mixture evaluation, improving the accuracy of QA in radiotherapy.

Transbronchial Techniques for Lung Cancer Treatment: Where Are We Now?

The demand for parenchyma-sparing local therapies for lung cancer is rising owing to an increasing incidence of multifocal lung cancers and patients who are unfit for surgery. With the latest evidence of the efficacy of lung cancer screening, more premalignant or early-stage lung cancers are being discovered and the paradigm has shifted from treatment to prevention. Transbronchial therapy is an important armamentarium in the local treatment of lung cancers, with microwave ablation being the most promising based on early to midterm results. Adjuncts to improve transbronchial ablation efficiency and accuracy include mobile C-arm platforms, software to correct for the CT-to-body divergence, metal-containing nanoparticles, and robotic bronchoscopy. Other forms of energy including steam vapor therapy and pulse electric field are under intensive investigation.

Traditional Treatment Approaches and Role of Immunotherapy in Lung Malignancy and Mesothelioma

There is no denying that many revolutions took place in the fight against cancer during the last decades. However, cancers have always managed to find new ways to challenge humankinds. Variable genomic epidemiology, socio-economic differences and limitations of widespread screening are the major concerns in cancer diagnosis and early treatment. A multidisciplinary approach is essentially to manage a cancer patient efficiently. Thoracic malignancies including lung cancers and pleural mesothelioma are accountable for little more than 11.6% of the global cancer burden [4]. Mesothelioma is one of the rare cancers, but concern is the incidences are increasing globally. However, the good news is first-line chemotherapy with the combination of immune checkpoints inhibitors (ICIs) in non-small cell lung cancer (NSCLC) and mesothelioma has showed promising respond and improved overall survival (OS) in pivotal clinical trials [10]. ICIs are commonly referred as immunotherapy are antigens on the cancer cells, and inhibitors are the antibodies produce by the T cell defence system. By inhibiting immune checkpoints, the cancer cells become visible to be identified as abnormal cells and attack by the body's defence system [17]. The programmed death receptor-1 (PD-1) and programmed death receptor ligand-1 (PD-L1) inhibitors are commonly used immune checkpoint blockers for anti-cancer treatment. PD-1/PD-L1 are proteins produced by immune cells and mimic by cancer cells that are implicated in inhibiting T cell response to regulate our immune system, which results tumour cells escaping the defence mechanism to achieve immune surveillance. Therefore, inhibiting immune checkpoints as well as monoclonal antibodies can lead to effective apoptosis of tumour cells [17]. Mesothelioma is an industrial disease caused by significant asbestos exposure. It is the cancer of the mesothelial tissue which presents in the lining of the mediastinum of pleura, pericardium and peritoneum, most commonly affected sites are pleura of the lung or chest wall lining [9] as route of asbestos exposure is inhalation. Calretinin is a calcium binding protein, typically over exposed in malignant mesotheliomas and the most useful marker even while initial changes take place [5]. On the other hand, Wilm's tumour 1 (WT-1) gene expression on the tumour cells can be related to prognosis as it can elicit immune response, thereby inhibit cell apoptosis. A systematic review and meta-analysis study conducted by Qi et al. has suggested that expression of WT-1 in a solid tumour is fatal however, it gives the tumour cell a feature of immune sensitivity which then acts positively towards the treatment with immunotherapy. Clinical significance of WT-1 oncogene in treatment is still hugely debatable and needs further attention [21]. Recently, Japan has reinstated Nivolumab in patients with chemo-refractory mesothelioma. According to NCCN guidelines, the salvage therapies include Pembrolizumab in PD-L1 positive patients and Nivolumab alone or with Ipilimumab in cancers irrespective of PD-L1 expression [9]. The checkpoint blockers have taken over the biomarker-based research and demonstrated impressive treatment options in immune sensitive and asbestos-related cancers. It can be expected that in near future the immune checkpoint inhibitors will be considered as approved first-line cancer treatment universally.

Real-World Evidence of Health Outcomes Related to Lung Stereotactic Body Radiation Therapy in Brazil

PURPOSE

Stereotactic body radiation therapy (SBRT) is an effective option for patients with both early-stage and oligometastatic non-small-cell lung cancer (NSCLC). However, data from Latin America are limited. Therefore, the aim of this study was to investigate the real-world outcomes of applying SBRT for lung lesions in a Brazilian institution.

METHODS

This study investigated a consecutive cohort of patients treated with SBRT for lung lesions (primary and metastasis). The study primary outcome was local control rates per lesion. Secondary outcomes included progression-free survival (PFS), overall survival (OS), and toxicity.

RESULTS

Between 2015 and 2019, a total of 216 patients received SBRT and were included in the study. The median follow-up was 24.5 months (5-70), primary NSCLC corresponded to 70% (n = 151) and nonprimary lung lesions to 30% (n = 65), respectively. Stage I NSCLC represented 56% (85 of 151) of the NSCLC cohort. The average number of fractions and total dose prescribed was 5 (3-10)/59 Gy (50-62 Gy). For stage I NSCLC (all lesions treated with a biologically effective dose [10] > 100 Gy), 2-year local control, OS, and PFS were 93.4%, 81.6%, and 80.7%, respectively. For stage IV lesions, if biologically effective dose (10) > 100 Gy or < 100 Gy, 2-year local control was 95.8/86.4% (P = .03), 2-year-OS was 81.6/60.5% (P = .006), and 2-year PFS was 38.9/17.9% (P = .10). Late toxicity was observed in 16.2% (n = 35) of the total cases.

CONCLUSION

Our results indicate that SBRT is effective (high local control and acceptable toxicity) for treating malignant lung lesions in a real-world scenario in Latin America.

CT patterns and serial CT Changes in lung Cancer patients post stereotactic body radiotherapy (SBRT)

Background

To evaluate computed tomography (CT) patterns of post-SBRT lung injury in lung cancer and identify time points of serial CT changes.

Materials and methods

One hundred eighty-three tumors in 170 patients were evaluated on sequential CTs within 29 months (median). Frequencies of post-SBRT CT patterns and time points of initiation and duration were assessed. Duration of increase of primary lesion or surrounding injury without evidence of local recurrence and time to stabilization or local recurrence were evaluated.

Results

Post-SBRT CT patterns could overlap in the same patient and were nodule-like pattern (69%), consolidation with ground glass opacity (GGO) (41%), modified conventional pattern (39%), peribronchial/patchy consolidation (42%), patchy GGO (24%), diffuse consolidation (16%), “orbit sign” (21%), mass-like pattern (19%), scar-like pattern (15%) and diffuse GGO (3%). Patchy GGO started at 4 months post-SBRT. Peribronchial/patchy consolidation and consolidation with GGO started at 4 and 5 months respectively. Diffuse consolidation, diffuse GGO and orbit sign started at 5, 6 and 8 months respectively. Mass-like, modified conventional and scar-like pattern started at 8, 12 and 12 months respectively. Primary lesion (n = 11) or surrounding injury (n = 85) increased up to 13 months. Primary lesion (n = 119) or surrounding injury (n = 115) started to decrease at 4 and 9 months respectively. Time to stabilization was 20 months. The most common CT pattern at stabilization was modified conventional pattern (49%), scar-like pattern (23%) and mass-like pattern (12%). Local recurrence (n = 15) occurred at a median time of 18 months.

Conclusion

Different CT patterns of lung injury post-SBRT appear in predictable time points and have variable but predictable duration. Familiarity with these patterns and timeframes of appearance helps differentiate them from local recurrence.

Role of Stereotactic Radiation Therapy in Operable and Inoperable Early-Stage Non-small Cell Lung Cancer

OPINION STATEMENT

Radiation therapy is becoming an increasingly important part of non-small cell lung cancer (NSCLC) management. Approximately 60% of all cancer patients require radiation therapy (RT) as part of their treatment. For lung cancer, this number is even higher, reaching approximately 77% of all patients, from radical to palliative modalities of RT. This percentage may even be underestimated, as it may not account for the more recent use of RT in oligometastatic lung cancer patients. Thus, we can estimate that each year there will be approximately 21,890 new lung cancer patients in the USA requiring RT. These numbers are expected to continue to rise, as lung cancer radiation techniques continue to improve. There is growing interest in determining the best treatment options for early-stage NSCLC patients. There is well-established data showing the benefit of RT for inoperable patients, and more recent encouraging data even in operable patients.

Applying PET-CT for predicting the efficacy of SBRT to inoperable early-stage lung adenocarcinoma: A Brazilian case-series

BACKGROUND

Stereotactic body radiotherapy (SBRT) is a treatment option for early-stage inoperable primary lung cancer. Here we report a thorough description of the prognostic value of pre-SBRT SUVmax for predicting the efficacy of SBRT in early-stage lung adenocarcinoma.

METHODS

This is a retrospective study of consecutive cases of early-stage inoperable lung adenocarcinoma, staged with PET-CT, treated with SBRT between 2007 and 17. Kaplan-Meier (KM) curves were used to assess overall survival and compare time to event between those with PET-CT SUVmax values ≤ 5.0 and those > 5. Fisher's Exact tests and the Mann-Whitney U were used to compare the patient and clinical data of those with SUVmax≤5.0 and >5.0, and those with and without any failure.

FINDINGS

Amongst 50 lung carcinoma lesions, from 47 patients (34 (68%)-T1a or <T1b), estimated median overall survival from the KM was 44.9 months (95% confidence interval 35.5-54.3). Five experienced a local failure, which was inadequate for detecting differences between those with PET-CT SUVmax ≤5.0 and those >5 (p = 0.112). In addition, 5 experienced a regional failure and 4 a distant failure. Higher PET-CT SUVmax values before SBRT were associated with an increased risk of any failure (36% versus 0%, p = 0.0040 on Fisher's Exact test) and faster time to event (p = 0.010, log rank test). Both acute and late toxicities profile were acceptable.

INTERPRETATION

Patients with early-stage inoperable lung adenocarcinoma present good clinical outcomes when treated with SBRT. We raised the hypothesis that the value of PET-CT SUVmax before SBRT may be an important predictive factor in disease control.

FUNDING

None.

Does irregular breathing impact on respiratory gated radiation therapy of lung stereotactic body radiation therapy treatments?

The impact of irregular breathing on respiratory gated radiation therapy (RGRT) was evaluated for lung stereotactic body radiation therapy (SBRT) treatments. Measurements in the static mode were performed with different field sizes, depths of the measurements, breathing periods and duty cycles, using the Farmer ion chamber, PinPoint ion chamber, and microDiamond detector. The output constancy (OC) was evaluated between gated and nongated beams. Measurements in the dynamic mode for regular and irregular breathing in phase- and amplitude-gated modes, were performed with the amplitude of target motion from 5 mm to 25 mm, and breathing period from 3 to 6 s, for ion chamber, and film inserts. The dose discrepancy was evaluated for the ion chamber insert. The gamma passing rate was evaluated with film dosimetry. In the static mode, the maximum obtained OC was 0.8% using the Farmer ion chamber, 1% (p < 0.001) using the microDiamond detector, and 1.4% (p < 0.001) using the PinPoint ion chamber. In the dynamic mode, good agreement between planned and measured doses was obtained for regular breathing, 2.08 ± 0.48% (1.57 to 2.74%), which increased to 3.42 ± 1.24% (1.58 to 6.69%) for irregular breathing. The gamma passing rate of 3mm/3%, 3mm/2%, 3mm/1% and 2mm/2% was 99.4% ± 0.3, 98.2 ± 0.8%, 88.2 ± 3.0% and 96.4 ± 1.0% for regular and 97.2% ± 1.6%, 95.1 ± 2.6%, 85.6 ± 3.0% and 92.9 ± 2.9% for irregular breathing patterns (p < 0.01), respectively. For a slightly irregular breathing amplitude, lung SBRT cancer patients can be treated in the phase-gated mode.

Access of Patients With Lung Cancer to High Technology Radiation Therapy in Brazil

PURPOSE

Lung cancer is a global health problem, with more than 220,000 new cases and 150,000 deaths per year in the United States. Likewise, in Brazil, lung cancer is the most lethal cancer with 30,200 new cases expected in 2020. Regarding treatment types, radiation therapy (RT) represents an important approach, since 60%-70% of the patients will receive this modality of treatment during the course of their disease. However, access to RT remains challenging because of the socioeconomic inequalities in the Brazilian population, where approximately 100,000 patients/year die without access to RT. This work provides an overview on the availability of high technology RT in Brazil.

METHODS

A retrospective study was performed using the Brazilian Radiotherapy Census, local public and private databases, and the current literature published in 2019.

RESULTS

The Brazilian radiotherapy network relies on approximately 363 linear accelerators and 20 cobalt machines that remain operational. Most of these machines are installed at public health facilities. Regarding high technology, intensity-modulated RT is available in 53.7% (n = 130) and volumetric modulated arc therapy in 28.5% (n = 69) of the institutions, although only 19.8% (n = 48) of those facilities are capable of performing image-guided RT using cone beam computed tomography. Considering only the public health care system, the scenario is more restricted, with 40.1% (n = 65) of the institutions offering intensity-modulated RT, 21% (n = 34) volumetric modulated arc therapy, and 14.8% (n = 24) using cone beam computed tomography. Because of these scare resources, only 16% of Radiation Departments offer stereotactic body RT.

CONCLUSION

Brazil still needs to improve and provide high and safer RT technologies to patients with lung cancer across all Brazilian regions to attend the population needs and obtain better patient outcomes.

Training and Validation of Deep Learning-Based Auto-Segmentation Models for Lung Stereotactic Ablative Radiotherapy Using Retrospective Radiotherapy Planning Contours

PURPOSE

Deep learning-based auto-segmented contour (DC) models require high quality data for their development, and previous studies have typically used prospectively produced contours, which can be resource intensive and time consuming to obtain. The aim of this study was to investigate the feasibility of using retrospective peer-reviewed radiotherapy planning contours in the training and evaluation of DC models for lung stereotactic ablative radiotherapy (SABR).

METHODS

Using commercial deep learning-based auto-segmentation software, DC models for lung SABR organs at risk (OAR) and gross tumor volume (GTV) were trained using a deep convolutional neural network and a median of 105 contours per structure model obtained from 160 publicly available CT scans and 50 peer-reviewed SABR planning 4D-CT scans from center A. DCs were generated for 50 additional planning CT scans from center A and 50 from center B, and compared with the clinical contours (CC) using the Dice Similarity Coefficient (DSC) and 95% Hausdorff distance (HD).

RESULTS

Comparing DCs to CCs, the mean DSC and 95% HD were 0.93 and 2.85mm for aorta, 0.81 and 3.32mm for esophagus, 0.95 and 5.09mm for heart, 0.98 and 2.99mm for bilateral lung, 0.52 and 7.08mm for bilateral brachial plexus, 0.82 and 4.23mm for proximal bronchial tree, 0.90 and 1.62mm for spinal cord, 0.91 and 2.27mm for trachea, and 0.71 and 5.23mm for GTV. DC to CC comparisons of center A and center B were similar for all OAR structures.

CONCLUSIONS

The DCs developed with retrospective peer-reviewed treatment contours approximated CCs for the majority of OARs, including on an external dataset. DCs for structures with more variability tended to be less accurate and likely require using a larger number of training cases or novel training approaches to improve performance. Developing DC models from existing radiotherapy planning contours appears feasible and warrants further clinical workflow testing.

Contribution of Imaging to Organs at Risk Dose during Lung Stereotactic Body Radiation Therapy

Background:

The use of imaging is indispensable in modern radiation therapy, both for simulation and treatment delivery. For safe and sure utilization, dose delivery from imaging must be evaluated.

Objective:

This study aims to investigate the dose to organ at risk (OAR) delivered by imaging during lung stereotactic body radiation therapy (SBRT) and to evaluate its contribution to the treatment total dose.

Material and Methods:

In this retrospectively study, imaging total dose to organs at risk (OARs) (spinal cord, esophagus, lungs, and heart) and effective dose were retrospectively evaluated from 100 consecutive patients of a single institution who had lung SBRT. For each patient, dose was estimated using Monte-Carlo convolution for helical computed tomography (helical CT), Four-Dimensional CT (4D-CT), and kilovoltage Cone-Beam CT (kV-CBCT). Helical CT and kV-CBCT dose were evaluated for the entire thorax acquisition, while 4D-CT dose was analyzed on upper lobe (UL) or lower lobe (LL) acquisition. Treatment dose was extracted from treatment planning system and compared to imaging total dose.

Results:

Imaging total dose maximum values were 117 mGy to the spinal cord, 127 mGy to the esophagus, 176 mGy to the lungs and 193 mGy to the heart. The maximum effective dose was 19.65 mSv for helical CT, 10.62 mSv for kV-CBCT, 25.95 mSv and 38.45 mSv for 4D-CT in UL and LL regions, respectively. Depending on OAR, treatment total dose was higher from 1.7 to 8.2 times than imaging total dose. Imaging total dose contributed only to 0.3% of treatment total dose.

Conclusion:

Imaging dose delivered with 4D-CT to the OARs is higher than those of others modalities. The heart received the highest imaging dose for both UL and LL. Total imaging dose is negligible since it contributed only to 0.3% of treatment total dose.

Non-surgical Treatments for Lung Metastases in Patients with Soft Tissue Sarcoma: Stereotactic Body Radiation Therapy (SBRT) and Radiofrequency Ablation (RFA)

BACKGROUND

Radio-frequency ablation (RFA) and Stereotactic Body Radiation Therapy (SBRT) are two emerging therapies for lung metastases.

INTRODUCTION

Aliterature review was performed to evaluate the outcomes and complications of these procedures in patients with lung metastases from soft tissue sarcoma (STS).

METHODS

After selection, seven studies were included for each treatment encompassing a total of 424 patients: 218 in the SBRT group and 206 in the RFA group.

RESULTS

The mean age ranged from 47.9 to 64 years in the SBRT group and from 48 to 62.7 years in the RFA group. The most common histologic subtype was, in both groups, leiomyosarcoma. In the SBRT group, median overall survival ranged from 25.2 to 69 months and median disease- free interval was from 8.4 to 45 months. Two out of seven studies reported G3 and one G3 toxicity, respectively. In RFA patients, overall survival ranged from 15 to 50 months. The most frequent complication was pneumothorax. Local control showed a high percentage for both procedures.

CONCLUSION

SBRT is recommended in patients unsuitable to surgery, in synchronous bilateral pulmonary metastases, in case of deep lesions and patients receiving high-risk systemic therapies. RFA is indicated in case of a long disease-free interval, in oligometastatic disease, when only the lung is involved, in small size lesions far from large vessels. Further large randomized studies are necessary to establish whether these treatments may also represent a reliable alternative to surgery.

A Minimal PKPD Interaction Model for Evaluating Synergy Effects of Combined NSCLC Therapies

This paper introduces a mathematical compartmental formulation of dose-effect synergy modelling for multiple therapies in non small cell lung cancer (NSCLC): antiangiogenic, immuno- and radiotherapy. The model formulates the dose-effect relationship in a unified context, with tumor proliferating rates and necrotic tissue volume progression as a function of therapy management profiles. The model accounts for inter- and intra-response variability by using surface model response terms. Slow acting peripheral compartments such as fat and muscle for drug distribution are not modelled. This minimal pharmacokinetic-pharmacodynamic (PKPD) model is evaluated with reported data in mice from literature. A systematic analysis is performed by varying only radiotherapy profiles, while antiangiogenesis and immunotherapy are fixed to their initial profiles. Three radiotherapy protocols are selected from literature: (1) a single dose 5 Gy once weekly; (2) a dose of 5 Gy × 3 days followed by a 2 Gy × 3 days after two weeks and (3) a dose of 5 Gy + 2 × 0.075 Gy followed after two weeks by a 2 Gy + 2 × 0.075 Gy dose. A reduction of 28% in tumor end-volume after 30 days was observed in Protocol 2 when compared to Protocol 1. No changes in end-volume were observed between Protocol 2 and Protocol 3, this in agreement with other literature studies. Additional analysis on drug interaction suggested that higher synergy among drugs affects up to three-fold the tumor volume (increased synergy leads to significantly lower growth ratio and lower total tumor volume). Similarly, changes in patient response indicated that increased drug resistance leads to lower reduction rates of tumor volumes, with end-volume increased up to 25–30%. In conclusion, the proposed minimal PKPD model has physiological value and can be used to study therapy management protocols and is an aiding tool in the clinical decision making process. Although developed with data from mice studies, the model is scalable to NSCLC patients.

Stereotactic Body Radiation Therapy for Biopsy-Proven Primary Non-Small-Cell Lung Cancer: Experience of Patients With Inoperable Cancer at a Single Brazilian Institution

Purpose

Stereotactic body radiation therapy (SBRT) has emerged as a treatment option for patients with non–small-cell lung cancer (NSCLC). We report the clinical outcomes and toxicity for patients with inoperable primary NSCLC treated with SBRT.

Methods

Between 2007 and 2015, 102 consecutive lung lesions were treated with SBRT at our center, of which 59 primary NSCLC lesions (from 54 patients with inoperable disease) were retrospectively reviewed (43 lesions were excluded because of metastases or because there was no biopsy specimen). We report infield local control (LC) per SBRT target, regional or distant failure-free survival, and overall survival (OS) per patient, using Kaplan-Meier estimates. Serious toxicity was retrospectively scored using Common Terminology Criteria for Adverse Events, version 4.

Results

Most of the 54 patients were men (n = 41; 76%), median age was 75 years; stage IA (n = 36; 66%) and adenocarcinoma (n = 43; 80%) were the most common stage and histologic diagnosis, respectively. Five patients had two lung lesions. A median of three fractions (range, 3 to 5 fractions) and a total median dose of 54 Gy (range, 45 to 60 Gy) per lesion were prescribed. The median follow-up was 17.8 months (range, 4 to 56.4 months). The 2-year rates of LC, regional or distant failure-free survival, and OS were 89.1% (95% CI, 72.2% to 96%), 79% (95% CI, 59.8% to 89.8%), and 80% (95% CI, 64% to 89.8%), respectively. Grade 3 to 4 toxicities were observed in two patients (3%): grade 3 pneumonitis (n = 1) and grade 4 skin toxicity (n = 1).

Conclusion

SBRT results in high rates of 2-year LC, regional or distant failure-free survival, and OS with low rates of severe toxicity in patients with inoperable primary NSCLC disease.

Clinical Outcomes of Stereotactic Body Radiotherapy in Oligometastatic Gynecological Cancer

OBJECTIVE

The objective of this study was to assess the role of stereotactic body radiotherapy (SBRT) in the treatment of distantly recurrent, oligometastatic gynecological cancer.

METHODS

The hospital records of 45 patients with F-fluorodeoxyglucose (F-FDG) positron emission tomography positive, distantly recurrent, oligometastatic gynecological cancer were reviewed. All these patients had a number of target lesions less than 5, with largest diameter less than 6 cm. The treatment was delivered with a TrueBeam LINAC and RapidArc technique, using 10 or 6 MV FFF beams. A total of 70 lesions were treated, and lymph nodes represented the most common site of metastases, followed by lung, liver, and soft tissues. Twenty lesions were treated with one single fraction of 24 Gy and 5 lesions received 27 Gy delivered in 3 fractions, depending on the ability to fulfill adequate target coverage and safe dose/volume constraints for the organ at risk with either regimen.

RESULTS

Positron emission tomography scan 3 months after SBRT showed a complete response (CR) in 45 lesions (64.3%), a partial response in 14 (20.0%), a stable disease in 5 (7.1%), and a progressive disease in 6 (8.6%). No lesions in CR after SBRT subsequently progressed. Overall acute toxicity occurred in 13 (28.9%) patients. The most common grade 1 to 2 adverse event was pain (n = 9, 20.0%), followed by nausea and vomiting (n = 5, 11.1%). No grade 3 to 4 acute toxicities occurred, and no late toxicities were observed. Patients who failed to achieve a CR had a 2.37-fold higher risk of progression and a 3.60-fold higher risk of death compared with complete responders (P = 0.04 and P = 0.03, respectively).

CONCLUSIONS

Stereotactic body radiotherapy offers an effective and safe approach for selected cases of oligometastatic gynecological cancer.