Advances in Treatment Techniques: Stereotactic Body Radiation Therapy and the Spread of Hypofractionation

The evolving role of radiation therapy as treatment for liver metastases

Liver metastases occur commonly in many solid malignancies. With advances in systemic therapies and increased life expectancy, the role of using local therapies in oligo-metastases is rapidly increasing. Stereotactic body radiotherapy (SBRT) is an emerging precision therapy that is being used more frequently in the treatment for unresectable liver metastases. This review focuses on the role of SBRT for liver metastases, principles of treatment, clinical outcomes, toxicity, and optimal patient selection.

Locoregional Therapies for Colorectal Cancer Liver Metastases: Options Beyond Resection

Colorectal cancer was the third most common malignancy worldwide in 2018, and most patients present with or develop distant metastases. Colorectal liver metastases are most commonly observed because of the vascular drainage of the colon and superior rectum. Current guidelines recommend surgical resection as first-line treatment; however, 80% to 90% of patients with colorectal liver metastases are ineligible for primary resection. For patients with unresectable disease, a multidisciplinary treatment approach is favored, incorporating systemic therapy and a toolbox of local ablative therapies. These treatments either aim at cytoreduction to enable a conversion to surgical resectability or control of disease progression and spread. Each of these treatments carries unique outcomes and risk profiles, thereby contributing to an individualized treatment strategy for patients with colorectal liver metastases. This review summarizes evidence on hepatic artery infusion, stereotactic body radiation therapy, thermal ablation, transarterial chemoembolization with drug-eluding beads, and transarterial radioembolization for treatment of colorectal liver metastases. Results of large-scale prospective and retrospective studies and international guidelines are discussed to provide detailed background on the current and prospective use of local ablative techniques in management of colorectal liver metastases.

Hypo-fractionation radiotherapy normalizes tumor vasculature in non-small cell lung cancer xenografts through the p-STAT3/HIF-1 alpha signaling pathway

Background:

Hypo-fractionation radiotherapy (HFRT) was considered to be an important treatment for non-small cell lung cancer (NSCLC), but the radiobiological effects of HFRT on NSCLC remain unclear. The aim of this study was to investigate specific biological effect of HFRT on tumor angiogenesis, compared with conventional radiotherapy (CRT).

Methods:

The subcutaneous xenograft models and the dorsal skinfold window chamber (DSWC) models of nude mice bearing H460 and HCC827 NSCLC cells were irradiated with doses of 0 Gy (sham group), 22 Gy delivered into 11 fractions (CRT group) or 12 Gy delivered into 1 fraction (HFRT group). At certain time-points after irradiation, the volumes, hypoxic area, coverage rate of pericyte and micro-vessel density (MVD) of the subcutaneous xenograft models were detected, and the tumor vasculature was visualized in the DSMC model. The expressions of phosphorylated signal transducer and activator of transcription (p-STAT3), hypoxia-inducible factor 1-α (HIF-1α), CXCL12 and VEGFA were detected.

Results:

Compared with the CRT groups, HFRT showed more-efficient tumor growth-suppression, accompanied by a HFRT-induced window-period, during which vasculature was normalized, tumor hypoxia was improved and MVD was decreased. Moreover, during the window-period, the signal levels of p-STAT3/HIF-1α pathway and the expressions of its downstream angiogenic factors (VEGFA and CXCL12) were inhibited by HFRT.

Conclusion:

Compared with CRT, HFRT induced tumor vasculature normalization by rendering the remaining vessels less tortuous and increasing pericyte coverage of tumor blood vessels, thereby ameliorating tumor hypoxia and enhancing the tumor-killing effect. Moreover, HFRT might exert the aforementioned effects through p-STAT3/HIF-1α signaling pathway.

A Noninvasive Method to Reduce Radiotherapy Positioning Error Caused by Respiration for Patients With Abdominal or Pelvic Cancers

Purpose:

To develop an infrared optical method of reducing surface-based registration error caused by respiration to improve radiotherapy setup accuracy for patients with abdominal or pelvic tumors.

Materials and Methods:

Fifteen patients with abdominal or pelvic tumors who received radiation therapy were prospectively included in our study. All patients were immobilized with vacuum cushion and underwent cone-beam computed tomography to validate positioning error before treatment. For each patient, after his or her setup based on markers fixed on immobilization device, initial positioning errors in patient left-right, anterior-posterior, and superior-inferior directions were validated by cone-beam computed tomography. Then, our method calculated mismatch between patient and immobilization device based on surface registration by interpolating between expiratory- and inspiratory-phase surface to find the specific phase to best match the surface in planning computed tomography scans. After adjusting the position of treatment couch by the shift proposed by our method, a second cone-beam computed tomography was performed to determine the final positioning error. A comparison between initial and final setup error will be made to validate the effectiveness of our method.

Results:

Final positioning error confirmed by cone-beam computed tomography is 1.59 (1.82), 1.61 (1.84), and 1.31 (1.38) mm, reducing initial setup error by 24.52%, 51.04%, and 53.63% in patient left-right, anterior-posterior, and superior-inferior directions, respectively. Wilcoxon test showed that our method significantly reduced the 3-dimensional distance of positioning error (P < .001).

Conclusion:

Our method can significantly improve the setup precision for patients with abdominal or pelvic tumors in a noninvasive way by reducing the surface-based registration error caused by respiration.

Radiation Dose-Volume Effects for Liver SBRT

Stereotactic body radiation therapy (SBRT) has emerged as an effective, noninvasive treatment option for primary liver cancer and metastatic disease occurring in the liver. Although SBRT can be highly effective for establishing local control in hepatic malignancies, a tradeoff exists between tumor control and normal tissue complications. The objective of the present study was to review the normal tissue dose-volume effects for SBRT-induced liver and gastrointestinal toxicities and derive normal tissue complication probability models.

Patterns of Fractionation and Boost Usage in Adjuvant External Beam Radiotherapy for Ductal Carcinoma in Situ in the United States

BACKGROUND

While the roles of hypofractionated (HFxn) radiotherapy and lumpectomy boost in the adjuvant management of invasive breast cancer are supported by the results of clinical trials, randomized data supporting their use for ductal carcinoma in situ (DCIS) are forthcoming. We sought to evaluate current national trends and identify factors associated with HFxn and boost usage using the National Cancer Database.

PATIENTS AND METHODS

We queried the National Cancer Database for women diagnosed with DCIS from 2004 to 2014 undergoing external beam radiotherapy after breast conservation surgery. Patients were categorized as receiving either conventional fractionation (CFxn) or HFxn and as either receiving or not receiving a boost. Multiple logistic regression was performed to identify demographic, clinical, and treatment factor associations.

RESULTS

A total of 101,615 women were identified, with 87,641 (86.2%) receiving CFxn, 13,974 (13.8%) receiving HFxn, and most patients in each group (84.9% and 57.7%, respectively) receiving a boost. Implementation of HFxn increased from 4.3% in 2004 to 33.0% in 2014, and the use of a boost declined from 83.3% to 74.6%. HFxn receipt was independently associated with later year of diagnosis, older age, higher income, greater distance from treatment facility, greater facility volume, academic facility type, Western residence, smaller lesions, and nonreceipt of a boost. Factors associated with boost receipt included earlier year of diagnosis, younger age, higher income, community facility type, adverse pathologic features, and nonreceipt of HFxn.

CONCLUSION

Although CFxn with a boost remains the most common external beam radiotherapy strategy for DCIS, implementation of HFxn without a boost appears to be increasing. Practice patterns at present seem to be driven by guidelines for invasive breast cancer and nonclinical factors.

Hypofractionated Intensity-Modulated Radiotherapy for Patients With Non-Small-Cell Lung Cancer

BACKGROUND

Alternative treatment regimens are needed for patients with non-small cell lung cancer (NSCLC) who cannot receive definitive treatment with concurrent chemoradiotherapy, surgery, or stereotactic ablative radiotherapy (SABR).

PATIENTS AND METHODS

We report survival, patterns of failure and toxicity outcomes for patients with NSCLC who were not eligible for surgical resection, concurrent chemoradiotherapy, or SABR and underwent hypofractionated intensity-modulated radiotherapy (IMRT). Kaplan-Meier survival analysis was used to evaluate the progression-free and overall survival. Competing risk analysis was used to evaluate in-field, locoregional, and distant failure.

RESULTS

A total of 42 patients treated to 52.5 to 60 Gy in 15 fractions were included. Most of the patients had metastatic or recurrent disease (64%) and a relatively large, centrally located tumor burden (74%). The median follow-up period was 13 months (interquartile range, 6-18 months). All patients received the total prescribed dose. The median survival was 15.1 months. The overall and progression-free survival rates at 1 year were 63% and 22.5%, respectively. The pattern of failure was predominantly distant, with only 2% of patients experiencing isolated in-field recurrence. The cumulative incidence of in-field failure at 6 and 12 months was 2.5% (95% confidence interval, 0.4%-15.6%) and 16.1% (95% confidence interval, 7.5%-34.7%), respectively. The risk of esophageal toxicity was associated with the esophageal mean dose, maximal point dose, and dose to the 5 cm³ volume. The risk of pneumonitis was associated with the lung mean dose and volume receiving 18 Gy.

CONCLUSION

Hypofractionated IMRT without concurrent chemotherapy provides favorable rates of local control and survival for well-selected patients with NSCLC who cannot tolerate standard definitive therapy.

Plasma ceramide, a real-time predictive marker of pulmonary and hepatic metastases response to stereotactic body radiation therapy combined with irinotecan

BACKGROUND AND PURPOSES

Early biomarkers of tumour response are needed to discriminate between responders and non-responders to radiotherapy. We evaluated the ability of ceramide, a bioactive sphingolipid, to predict tumour sensitivity in patients treated by hypofractionated stereotactic body radiation therapy (SBRT) combined with irinotecan chemotherapy.

MATERIALS AND METHODS

Plasma levels of total ceramide and of its subspecies were measured before and during treatment in 35 patients with liver and lung oligometastases of colorectal cancer included in a phase II trial. Cer levels were quantified by LC-ESI-MS/MS and compared to tumour volume response evaluated one year later by CT-scan.

RESULTS

Pretreatment plasma ceramide levels were not indicative of tumour response. Nevertheless, the levels of total ceramide and of its 4 main subspecies were significantly higher at days 3 and 10 of treatment in objective responders than in non-responders. According to Kaplan-Meier curves, almost complete tumour control was achieved at 1year in patients with increased total ceramide levels whereas 50% of patients with decreased levels experienced an increase in tumour volume.

CONCLUSIONS

Total plasma ceramide is a promising biomarker of tumour response to SBRT combined with irinotecan that should enable to segregate patients with high risk of tumour escape.

Three-dimensional conformal radiation therapy in the liver: MRI findings along a time continuum

Recent development of 3-dimensional conformal radiation therapies provides a concentrated radiation dose to the tumor. To achieve this goal, a complex design of multiple narrow beamlets is used to shape the radiation exposure to conform to the shape of the tumor. Imaging findings after novel radiation therapy techniques differ from those of conventional radiation therapy. This article discusses changes in the liver parenchyma and tumor after conformal radiation therapy focusing on magnetic resonance imaging.

Cancer-associated fibroblasts from lung tumors maintain their immunosuppressive abilities after high-dose irradiation

Accumulating evidence supports the notion that high-dose (>5 Gy) radiotherapy (RT) regimens are triggering stronger pro-immunogenic effects than standard low-dose (2 Gy) regimens. However, the effects of RT on certain immunoregulatory elements in tumors remain unexplored. In this study, we have investigated the effects of high-dose radiotherapy (HD-RT) on the immunomodulating functions of cancer-associated fibroblasts (CAFs). Primary CAF cultures were established from lung cancer specimens derived from patients diagnosed for non-small cell lung cancer. Irradiated and non-irradiated CAFs were examined for immunomodulation in experiments with peripheral blood mononuclear cells from random, healthy donors. Regulation of lymphocytes behavior was checked by lymphocyte proliferation assays, lymphocyte migration assays, and T-cell cytokine production. Additionally, CAF-secreted immunoregulatory factors were studied by multiplex protein arrays, ELISAs, and by LC-MS/MS proteomics. In all functional assays, we observed a powerful immunosuppressive effect exerted by CAF-conditioned medium on activated T-cells (p > 0.001), and this effect was sustained after a single radiation dose of 18 Gy. Relevant immunosuppressive molecules such as prostaglandin E2, interleukin-6, and -10, or transforming growth factor-β were found in CAF-conditioned medium, but their secretion was unchanged after irradiation. Finally, immunogenic cell death responses in CAFs were studied by exploring the release of high motility group box-1 and ATP. Both alarmins remained undetectable before and after irradiation. In conclusion, CAFs play a powerful immunosuppressive effect over activated T-cells, and this effect remains unchanged after HD-RT. Importantly, CAFs do not switch on immunogenic cell death responses after exposure to HD-RT.

Adaptive motion mapping in pancreatic SBRT patients using Fourier transforms

BACKGROUND AND PURPOSE

Recent studies suggest that 4DCT is unable to accurately measure respiratory-induced pancreatic tumor motion. In this work, we assessed the daily motion of pancreatic tumors treated with SBRT, and developed adaptive strategies to predict and account for this motion.

MATERIALS AND METHODS

The daily motion trajectory of pancreatic tumors during CBCT acquisition was calculated using a model which reconstructs the instantaneous 3D position in each 2D CBCT projection image. We developed a metric (termed "Spectral Coherence," SC) based on the Fourier frequency spectrum of motion in the SI direction, and analyzed the ability of SC to predict motion-based errors and classify patients according to motion characteristics.

RESULTS

The amplitude of daily motion exceeded the predictions of pre-treatment 4DCT imaging by an average of 3.0mm, 2.3mm, and 3.5mm in the AP/LR/SI directions. SC was correlated with daily motion differences and tumor dose coverage. In a simulated adaptive protocol, target margins were adjusted based on SC, resulting in significant increases in mean target D95, D99, and minimum dose.

CONCLUSION

Our Fourier-based approach differentiates between consistent and inconsistent motion characteristics of respiration and correlates with daily motion deviations from pre-treatment 4DCT. The feasibility of an SC-based adaptive protocol was demonstrated, and this patient-specific respiratory information was used to improve target dosimetry by expanding coverage in inconsistent breathers while shrinking treatment volumes in consistent breathers.

Frontiers in radiotherapy for early-stage invasive breast cancer

The development of breast-conserving treatment for early-stage breast cancer is one of the most important success stories in radiation oncology in the latter half of the twentieth century. Lumpectomy followed by radiotherapy provides an appealing alternative to mastectomy for many women. In recent years, there has been a shift in clinical investigational focus toward refinements in the methods of delivering adjuvant radiotherapy that provide shorter, more convenient schedules of external-beam radiotherapy and interstitial treatment. Expedited courses of whole-breast treatment have been demonstrated to be equivalent to traditional lengthier courses in terms of tumor control and cosmetic outcome and to provide an opportunity for cost efficiencies.

Radiotherapy and the tumor stroma: the importance of dose and fractionation

Ionizing radiation is a non-specific but highly effective way to kill malignant cells. However, tumor recurrence sustained by a minor fraction of surviving tumor cells is a commonplace phenomenon caused by the activation of both cancer cell intrinsic resistance mechanisms, and also extrinsic intermediaries of therapy resistance, represented by non-malignant cells and structural components of the tumor stroma. The improved accuracy offered by advanced radiotherapy (RT)-technology permits reduced volume of healthy tissue in the irradiated field, and has been triggering an increase in the prescription of high-dose oligo-fractionated regimens in the clinics. Given the remarkable clinical success of high-dose RT and the current therapeutic shift occurring in the field, in this review we revise the existing knowledge on the effects that different radiation regimens exert on the different compartments of the tumor microenvironment, and highlight the importance of anti-tumor immunity and other tumor cell extrinsic mechanisms influencing therapeutic responses to high-dose radiation.

Molecular imaging to identify tumor recurrence following chemoradiation in a hostile surgical environment

Surgical biopsy of potential tumor recurrence is a common challenge facing oncologists, surgeons, and cancer patients. Imaging modalities have limited ability to accurately detect recurrent cancer in fields affected by previous surgery, chemotherapy, or radiation. However, definitive tissue diagnosis is often needed to initiate treatment and to direct therapy. We sought to determine if a targeted fluorescent intraoperative molecular imaging technique could be applied in a clinical setting to assist a surgical biopsy in a "hostile" field. We describe the use of a folate-fluorescein conjugate to direct the biopsy of a suspected recurrent lung adenocarcinoma invading the mediastinum that had been previously treated with chemoradiation. We found that intraoperative imaging allowed the identification of small viable tumor deposits that were otherwise indistinguishable from scar and necrosis. Our operative observations were confirmed by histology, fluorescence microscopy, and immunohistochemistry. Our results demonstrate one possible application and clinical value of intraoperative molecular imaging.

Effect of endorectal balloon positioning errors on target deformation and dosimetric quality during prostate SBRT

An inflatable endorectal balloon (ERB) is often used during stereotactic body radiation therapy (SBRT) for treatment of prostate cancer in order to reduce both intrafraction motion of the target and risk of rectal toxicity. However, the ERB can exert significant force on the prostate, and this work assessed the impact of ERB position errors on deformation of the prostate and treatment dose metrics. Seventy-one cone-beam computed tomography (CBCT) image datasets of nine patients with clinical stage T1cN0M0 prostate cancer were studied. An ERB (Flexi-Cuff, EZ-EM, Westbury, NY) inflated with 60 cm(3) of air was used during simulation and treatment, and daily kilovoltage (kV) CBCT imaging was performed to localize the prostate. The shape of the ERB in each CBCT was analyzed to determine errors in position, size, and shape. A deformable registration algorithm was used to track the dose received by (and deformation of) the prostate, and dosimetric values such as D95, PTV coverage, and Dice coefficient for the prostate were calculated. The average balloon position error was 0.5 cm in the inferior direction, with errors ranging from 2 cm inferiorly to 1 cm superiorly. The prostate was deformed primarily in the AP direction, and tilted primarily in the anterior-posterior/superior-inferior plane. A significant correlation was seen between errors in depth of ERB insertion (DOI) and mean voxel-wise deformation, prostate tilt, Dice coefficient, and planning-to-treatment prostate inter-surface distance (p < 0.001). Dosimetrically, DOI is negatively correlated with prostate D95 and PTV coverage (p < 0.001). For the model of ERB studied, error in ERB position can cause deformations in the prostate that negatively affect treatment, and this additional aspect of setup error should be considered when ERBs are used for prostate SBRT. Before treatment, the ERB position should be verified, and the ERB should be adjusted if the error is observed to exceed tolerable values.

Present and future innovations in radiation oncology

The purpose of this article is to provide a review of innovations in radiation oncology that have been recently adopted as well as those that are likely to be adopted in the near future. Physics and engineering innovations, including image-guidance technologies and charged particle therapy, are discussed. Biologic innovations, including novel radiation sensitizers, functional imaging for use in treatment planning, and altered fractionation, are also discussed.

Ablative hypofractionated radiotherapy normalizes tumor vasculature in lewis lung carcinoma mice model

Ablative hypofractionated radiotherapy (HFRT) significantly improves the overall survival of inoperable non-small cell lung cancer (NSCLC) patients compared with conventional radiation therapy. However, the radiobiological mechanisms of ablative HFRT remain largely unknown. The purpose of this study was to investigate the dynamic changes of tumor vessels and perfusion during and after ablative hypofractionated radiotherapy. Lewis lung carcinoma-bearing mice were treated with sham (control) and ablative hypofractionated radiotherapy of 12 Gy in 1 fraction (12 Gy/1F) and 36 Gy in 3 fractions (36 Gy/3F). Tumor microvessel density (MVD), morphology and function were examined at different times after irradiation. The results showed that, compared to the controls the MVD and hypoxia in ablative HFRT groups decreased, which were accompanied by an increase in the number of pericytes and their coverage of vessels. Functional tests revealed that tumor hypoxia and perfusion were improved, especially in the 36 Gy/3F group. Our results revealed that ablative hypofractionated radiotherapy not only repressed MVD and hypoxia, but also increased the vascular perfusion and the number of pericyte-covered vessels, suggesting that ablative HFRT normalized the tumor vasculature.

Changes in the Secretory Profile of NSCLC-Associated Fibroblasts after Ablative Radiotherapy: Potential Impact on Angiogenesis and Tumor Growth

In the context of radiotherapy, collateral effects of ablative doses of ionizing radiation (AIR) on stromal components of tumors remains understudied. In this work, cancer-associated fibroblasts (CAFs) isolated from freshly resected human lung tumors were exposed to AIR (1x 18 Gy) and analyzed for their release of paracrine factors. Inflammatory mediators and regulators of angiogenesis and tumor growth were analyzed by multiplex protein assays in conditioned medium (CM) from irradiated and non-irradiated CAFs. Additionally, the profile of secreted proteins was examined by proteomics. In functional assays, effects of CAF-CM on proliferative and migratory capacity of lung tumor cells (H-520/H-522) and human umbilical vein endothelial cells (HUVECs) and their tube-forming capacity were assessed. Our data show that exposure of CAFs to AIR results in 1) downregulated release of angiogenic molecules such as stromal cell-derived factor-1, angiopoietin, and thrombospondin-2 (TSP-2); 2) upregulated release of basic fibroblast growth factor from most donors; and 3) unaffected expression levels of hepatocyte growth factor, interleukin-6 (IL-6), IL-8, IL-1β, and tumor necrosis factor-α. CM from irradiated and control CAFs did not affect differently the proliferative or migratory capacity of tumor cells (H-520/H-522), whereas migratory capacity of HUVECs was partially reduced in the presence of irradiated CAF-CM. Overall, we conclude that AIR mediates a transformation on the secretory profile of CAFs that could influence the behavior of other cells in the tumor tissue and hence guide therapeutic outcomes. Downstream consequences of the changes observed in this study merits further investigations.

Cancer-associated fibroblasts from human NSCLC survive ablative doses of radiation but their invasive capacity is reduced

Background

Cancer-Associated Fibroblasts (CAFs) are significant components of solid malignancies and play central roles in cancer sustainability, invasion and metastasis. In this study we have investigated the invasive capacity and matrix remodelling properties of human lung CAFs after exposure to ablative doses of ionizing radiation (AIR), equivalent to single fractions delivered by stereotactic ablative radiotherapy (SART) for medically inoperable stage-I/II non-small-cell lung cancers.

Methods

CAFs were isolated from lung tumour specimens from 16 donors. Initially, intrinsic radiosensitivity was evaluated by checking viability and extent of DNA-damage response (DDR) at different radiation doses. The migrative and invasive capacities of CAFs were thereafter determined after a sub-lethal single radiation dose of 18 Gy. To ascertain the mechanisms behind the altered invasive capacity of cells, expression of matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) were measured in the conditioned media several days post-irradiation, along with expression of cell surface integrins and dynamics of focal contacts by vinculin-staining.

Results

Exposing CAFs to 1 × 18 Gy resulted in a potent induction of multiple nuclear DDR foci (> 9/cell) with little resolution after 120 h, induced premature cellular senescence and inhibition of the proliferative, migrative and invasive capacity. AIR promoted MMP-3 and inhibited MMP-1 appearance to some extent, but did not affect expression of other major MMPs. Furthermore, surface expression of integrins α2, β1 and α5 was consistently enhanced, and a dramatic augmentation and redistribution of focal contacts was observed.

Conclusions

Our data indicate that ablative doses of radiation exert advantageous inhibitory effects on the proliferative, migratory and invasive capacity of lung CAFs. The reduced motility of irradiated CAFs might be a consequence of stabilized focal contacts via integrins.