Late tumor pseudoprogression followed by complete remission after lung stereotactic ablative radiotherapy

Pseudo-progression with osimertinib after definitive chemoradiation in unresectable epidermal growth factor receptor mutation positive of stage III non-small cell lung cancer: A case report

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) have been widely used in the treatment of locally advanced non-small cell lung cancer (NSCLC). The phenomenon of pseudoprogression in targeted therapy in EGFR-mutation NSCLC patients is rare. Here, we reported an EGFR-mutation-positive lung adenocarcinoma patient who was admitted to a hospital for cough and chest distress accompanied by shortness of breath. He underwent four cycles of chemotherapy with pemetrexed combined with carboplatin and concurrent radiotherapy in the third and fourth cycles. Then, he was treated by osimertinib maintenance therapy. After 11.5 months of osimertinib treatment, he was assessed to progressive disease by computed tomography. He underwent fiber bronchoscopy, and the biopsy pathology showed extensive necrosis without tumor cells. Until now, the patient has continued on osimertinib for 7 months without relapse or metastasis. As far as we know, we are the first to report pseudoprogression in osimertinib maintenance after definitive chemoradiation. This study reminds the clinicians to distinguish pseudoprogression from osimertinib-induced progression and avoid abandoning effective treatments.

Imaging response assessment following stereotactic body radiotherapy for solid tumour metastases of the spine: Current challenges and future directions

Patients with metastatic disease are routinely serially imaged to assess disease burden and response to systemic and local therapies, which places ever-expanding demands on our healthcare resources. Image interpretation following stereotactic body radiotherapy (SBRT) for spine metastases can be challenging; however, appropriate and accurate assessment is critical to ensure patients are managed correctly and resources are optimised. Here, we take a critical review of the merits and pitfalls of various imaging modalities, current response assessment guidelines, and explore novel imaging approaches and the potential for radiomics to add value in imaging assessment.

Incidence and Time of Onset of Osseous Pseudoprogression in Patients With Metastatic Spine Disease From Renal Cell or Prostate Carcinoma After Treatment With Stereotactic Body Radiation Therapy

BACKGROUND

Tumor osseous pseudoprogression (PP), defined as an imaging-based transient increase in tumor size following treatment, was recently described in patients with spinal metastases following stereotactic body radiation therapy. Distinguishing PP from true tumor progression is critical.

OBJECTIVE

To describe the incidence, time of onset, and time range of PP following stereotactic body radiation therapy in patients treated for spinal metastases from either prostate cancer (PC) or renal cell carcinoma (RCC), and associated predictive factors.

METHODS

A retrospective study was conducted on our institution's cancer database from 2009 to 2015. Selection was based on single level, no prior radiation or surgery, ≥2 follow-up spine magnetic resonance imaging (MRI), and metastases arising from either PC or RCC. Gross tumor volume was contoured on pre- and up to 5 posttreatment MRIs. Patients were sorted into groups depending on gross tumor volume response: PP, non-PP, or progressive disease. Clinical and dosimetric variables were compared using either Fisher's exact test or Kruskal-Wallis analyses.

RESULTS

Forty-three spinal segments from 31 patients were analyzed. RCC and PC patients showed similar incidence of PP (∼37%). Whether the primary was lytic or sclerotic was a significant predictive factor with more PP in the lytic group (P = .0208). There was a trend of earlier PP onset in RCC (within 6-18 mo) as compared to PC; however, PC segments showed more time-confined presentation of PP (9-12 mo).

CONCLUSION

There was a higher incidence of PP in lytic compared to sclerotic primary tumor type. PP in spinal metastatic sites may have variable presentations depending on the primary cancer.

Role of noninvasive molecular imaging in determining response

The intersection of immunotherapy and radiation oncology is a rapidly evolving area of preclinical and clinical investigation. The strategy of combining radiation and immunotherapy to enhance local and systemic antitumor immune responses is intriguing yet largely unproven in the clinical setting because the mechanisms of synergy and the determinants of therapeutic response remain undefined. In recent years, several noninvasive molecular imaging approaches have emerged as a platform to interrogate the tumor immune microenvironment. These tools have the potential to serve as robust biomarkers for cancer immunotherapy and may hold several advantages over conventional anatomic imaging modalities and contemporary invasive tissue acquisition techniques. Given the key and expanding role of precision imaging in radiation oncology for patient selection, target delineation, image guided treatment delivery, and response assessment, noninvasive molecular-specific imaging may be uniquely suited to evaluate radiation/immunotherapy combinations. Herein, we describe several experimental imaging-based strategies that are currently being explored to characterize in vivo immune responses, and we review a growing body of preclinical data and nascent clinical experience with immuno-positron emission tomography molecular imaging as a putative biomarker for cancer immunotherapy. Finally, we discuss practical considerations for clinical translation to implement noninvasive molecular imaging of immune checkpoint molecules, immune cells, or associated elements of the antitumor immune response with a specific emphasis on its potential application at the interface of radiation oncology and immuno-oncology.

A Study of Pseudoprogression After Spine Stereotactic Body Radiation Therapy

PURPOSE

To determine the incidence of pseudoprogression (PP) after spine stereotactic body radiation therapy based on a detailed and quantitative assessment of magnetic resonance imaging (MRI) morphologic tumor alterations, and to identify predictive factors distinguishing PP from local recurrence (LR).

METHODS AND MATERIALS

A retrospective analysis of 35 patients with 49 spinal segments treated with spine stereotactic body radiation therapy, from 2009 to 2014, was conducted. The median number of follow-up MRI studies was 4 (range, 2-7). The gross tumor volumes (GTVs) within each of the 49 spinal segments were contoured on the pretreatment and each subsequent follow-up T1- and T2-weighted MRI sagittal sequence. T2 signal intensity was reported as the mean intensity of voxels constituting each volume. LR was defined as persistent GTV enlargement on ≥2 serial MRI studies for ≥6 months or on pathologic confirmation. PP was defined as a GTV enlargement followed by stability or regression on subsequent imaging within 6 months. Kaplan-Meier analysis was used for estimation of actuarial local control, disease-free survival, and overall survival.

RESULTS

The median follow-up was 23 months (range, 1-39 months). PP was identified in 18% of treated segments (9 of 49) and LR in 29% (14 of 49). Earlier volume enlargement (5 months for PP vs 15 months for LR, P=.005), greater GTV to reference nonirradiated vertebral body T2 intensity ratio (+30% for PP vs -10% for LR, P=.005), and growth confined to 80% of the prescription isodose line (80% IDL) (8 of 9 PP cases vs 1 of 14 LR cases, P=.002) were associated with PP on univariate analysis. Multivariate analysis confirmed an earlier time to volume enlargement and growth within the 80% IDL as significant predictors of PP. LR involved the epidural space in all but 1 lesion, whereas PP was confined to the vertebral body in 7 of 9 cases.

CONCLUSIONS

PP was observed in 18% of treated spinal segments. Tumor growth confined to the 80% IDL and earlier time to tumor enlargement were predictive for PP.

Pulmonary imaging after stereotactic radiotherapy-does RECIST still apply?

The use of stereotactic ablative radiotherapy (SABR) for the treatment of primary lung cancer and metastatic disease is rapidly increasing. However, the presence of benign fibrotic changes on CT imaging makes response assessment following SABR a challenge, as these changes develop with an appearance similar to tumour recurrence. Misclassification of benign fibrosis as local recurrence has resulted in unnecessary interventions, including biopsy and surgical resection. Response evaluation criteria in solid tumours (RECIST) are widely used as a universal set of guidelines to assess tumour response following treatment. However, in the context of non-spherical and irregular post-SABR fibrotic changes, the RECIST criteria can have several limitations. Positron emission tomography can also play a role in response assessment following SABR; however, false-positive results in regions of inflammatory lung post-SABR can be a major clinical issue and optimal standardized uptake values to distinguish fibrosis and recurrence have not been determined. Although validated CT high-risk features show a high sensitivity and specificity for predicting recurrence, most recurrences are not detected until more than 1-year post-treatment. Advanced quantitative radiomic analysis on CT imaging has demonstrated promise in distinguishing benign fibrotic changes from local recurrence at earlier time points, and more accurately, than physician assessment. Overall, the use of RECIST alone may prove inferior to novel metrics of assessing response.

Mechanism and non-mechanism based imaging biomarkers for assessing biological response to treatment in non-small cell lung cancer

Therapeutic options in locally advanced non-small cell lung cancer (NSCLC) have expanded in the past decade to include a palate of targeted interventions such as high dose targeted thermal ablations, radiotherapy and growing platform of antibody and small molecule therapies and immunotherapies. Although these therapies have varied mechanisms of action, they often induce changes in tumour architecture and microenvironment such that response is not always accompanied by early reduction in tumour mass, and evaluation by criteria other than size is needed to report more effectively on response. Functional imaging techniques, which probe the tumour and its microenvironment through novel positron emission tomography and magnetic resonance imaging techniques, offer more detailed insights into and quantitation of tumour response than is available on anatomical imaging alone. Use of these biomarkers, or other rational combinations as readouts of pathological response in NSCLC have potential to provide more accurate predictors of treatment outcomes. In this article, the robustness of the more commonly available positron emission tomography and magnetic resonance imaging biomarker indices is examined and the evidence for their application in NSCLC is reviewed.

Follow-up of patients after stereotactic radiation for lung cancer: a primer for the nonradiation oncologist

BACKGROUND

The use of stereotactic ablative radiotherapy (SABR) as primary treatment for early stage non-small-cell lung cancer, or for ablation of metastases, has increased rapidly in the past decade. With local recurrence rates reported at approximately 10%, and a patient population that is becoming increasingly fit and amenable to salvage treatment, appropriate multidisciplinary follow-up care is critical. Appropriate follow-up will allow for detection and management of radiation-related toxicity, early detection of recurrent disease and differentiation of recurrence from radiation-induced lung injury.

METHODS

This narrative review summarizes issues surrounding follow-up of patients treated with SABR in the context of a multidisciplinary perspective. We summarize treatment-related toxicities including radiation pneumonitis, chest wall pain, rib fracture, and fatal toxicity, and highlight the challenges of early and accurate detection of local recurrence, while avoiding unnecessary biopsy or treatment of benign radiation-induced fibrotic lung damage.

RESULTS

Follow-up recommendations based on the current evidence and available guidelines are summarized. Imaging follow-up recommendations include serial computed tomography (CT) imaging at 3-6 months posttreatment for the initial year, then every 6-12 months for an additional 3 years, and annually thereafter. With suspicion of progressive disease, recommendations include a multidisciplinary team discussion, the use of high-risk CT features for accurate detection of local recurrence, and positron emission tomography/CT SUV max cutoffs to prompt further investigation. Biopsy and/or surgical or nonsurgical salvage therapy can be considered if safe and when investigations are nonreassuring.

CONCLUSIONS

The appropriate follow-up of patients after SABR requires collaborative input from nearly all members of the thoracic multidisciplinary team, and evidence is available to guide treatment decisions. Further research is required to develop better predictors of toxicity and recurrence.

New techniques for assessing response after hypofractionated radiotherapy for lung cancer

Hypofractionated radiotherapy (HFRT) is an effective and increasingly-used treatment for early stage non-small cell lung cancer (NSCLC). Stereotactic ablative radiotherapy (SABR) is a form of HFRT and delivers biologically effective doses (BEDs) in excess of 100 Gy10 in 3-8 fractions. Excellent long-term outcomes have been reported; however, response assessment following SABR is complicated as radiation induced lung injury can appear similar to a recurring tumor on CT. Current approaches to scoring treatment responses include Response Evaluation Criteria in Solid Tumors (RECIST) and positron emission tomography (PET), both of which appear to have a limited role in detecting recurrences following SABR. Novel approaches to assess response are required, but new techniques should be easily standardized across centers, cost effective, with sensitivity and specificity that improves on current CT and PET approaches. This review examines potential novel approaches, focusing on the emerging field of quantitative image feature analysis, to distinguish recurrence from fibrosis after SABR.