Pembrolizumab-induced Radiation Recall Pneumonitis After the Resolution of Typical Asymptomatic Radiation Pneumonitis

Imaging Follow-Up of Nonsurgical Therapies for Lung Cancer: AJR Expert Panel Narrative Review

Lung cancer continues to be the most common cause of cancer-related death worldwide. In the past decade, with the implementation of lung cancer screening programs and advances in surgical and nonsurgical therapies, the survival of patients with lung cancer has increased, as has the number of imaging studies that these patients undergo. However, most patients with lung cancer do not undergo surgical re-section, because they have comorbid disease or lung cancer in an advanced stage at diagnosis. Nonsurgical therapies have continued to evolve with a growing range of systemic and targeted therapies, and there has been an associated evolution in the imaging findings encountered at follow-up examinations after such therapies (e.g., with respect to posttreatment changes, treatment complications, and recurrent tumor). This AJR Expert Panel Narrative Review describes the current status of nonsurgical therapies for lung cancer and their expected and unexpected imaging manifestations. The goal is to provide guidance to radiologists regarding imaging assessment after such therapies, focusing mainly on non-small cell lung cancer. Covered therapies include systemic therapy (conventional chemotherapy, targeted therapy, and immunotherapy), radiotherapy, and thermal ablation.

Radiation Recall Pneumonitis: A Rare Syndrome That Should Be Recognized

Simple Summary

A combination of radiotherapy and systemic antineoplastic agents is a common treatment strategy for lung cancer. However, Radiation recall pneumonitis (RRP) is a rare disease which has been mainly detected in the previously irradiated lung of patients with cancer after the application of triggering agents, including, but not limited to, antineoplastic agents. Physicians should be aware of this rare reaction, as the occurrence of RRP could impact the outcome of anti-cancer treatment. Given that current studies on RRP are primarily case reports and retrospectively reviewed data, the aim of our article was to review the current understanding and evidence on RRP and define the characteristics of RRP.

Abstract

Radiation recall pneumonitis (RRP) is a rare but severe condition which has been mainly detected in the previously irradiated lung of patients with cancer after administering inciting agents, most commonly antineoplastic regimens including chemotherapy, targeted therapy, or immunotherapy. More recently, coronavirus disease vaccines were found to induce RRP. In addition to typical radiation pneumonitis (RP) or drug-induced interstitial lung disease, the management of RRP requires withholding inciting agents and steroid therapy. Thus, the occurrence of RRP could significantly impact cancer treatment, given that inciting agents are withheld temporarily and even discontinued permanently. In the present review, we discuss the current understanding and evidence on RRP and provide additional insights into this rare but severe disease.

Radiation recall pneumonitis triggered by an immune checkpoint inhibitor following re-irradiation in a lung cancer patient: a case report

Background

Radiation recall pneumonitis (RRP) is unpredictable but associated with severe radiation damage in previously irradiated fields. Chemotherapy and targeted drugs have been reported to contribute to RRP. Here we report a case of a patient with non-small cell lung cancer (NSCLC) who developed RRP following administration of immune checkpoint inhibitor (ICI) 18 months after the end of re-irradiation.

Case presentation

A 69-year-old man received adjuvant chemoradiotherapy post-operatively. He underwent thoracic re-irradiation for oligometastatic NSCLC. On second recurrence, pembrolizumab combined with nab-paclitaxel were administered. After six months, he developed symptoms of persistent cough and dyspnea, with consistent pneumonitis on CT images. The clinical time frame and significant radiographic evidence raised suspicion for RRP. Symptoms resolved after steroids.

Conclusions

RRP is a rare occurrence. Patients undergoing immunotherapy after prior irradiation may be at increased risk of this rare radiation pneumonitis.

The Research Progress of PD-1/PD-L1 Inhibitors Enhancing Radiotherapy Efficacy

Approximately 60%–70% of patients with malignant tumours require radiotherapy. The clinical application of immune checkpoint inhibitors (ICIs), such as anti-PD-1/PD-L1, has revolutionized cancer treatment and greatly improved the outcome of a variety of cancers by boosting host immunity.However, radiotherapy is a double-edged sword for PD-1/PD-L immunotherapy. Research on how to improve radiotherapy efficacy using PD-1/PD-L1 inhibitor is gaining momentum. Various studies have reported the survival benefits of the combined application of radiotherapy and PD-1/PD-L1 inhibitor. To fully exerts the immune activation effect of radiotherapy, while avoiding the immunosuppressive effect of radiotherapy as much as possible, the dose selection, segmentation mode, treatment timing and the number of treatment sites of radiotherapy play a role. Therefore, we aim to review the effect of radiotherapy combined with anti-PD-1/PD-L1 on the immune system and its optimization.

Risk factors for radiation-induced lung injury in patients with advanced non-small cell lung cancer: implication for treatment strategies

BACKGROUND

The radiation-induced lung injury (RILI) in patients with advanced non-small cell lung cancer (NSCLS) is very common in clinical settings; we aimed to evaluate the risk factors of RILI in NSCLS patients, to provide insights into the treatment of NSCLS.

METHODS

NSCLC patients undergoing three-dimensional conformal radiotherapy (3D-CRT) in our hospital from June 1, 2018, to June 30, 2020, were included. The characteristics and treatments of RILI and non-RILI patients were analyzed. Logistic regression analyses were conducted to assess the risk factors of RILI in patients with NSCLC.

RESULTS

A total of 126 NSCLC patients were included; the incidence of RILI in NSCLC patients was 35.71%. There were significant differences in diabetes, smoke, chronic obstructive pulmonary disease (COPD), concurrent chemotherapy, radiotherapy dose, and planning target volume (PTV) between the RILI group and the non-RILI group (all P < 0.05). Logistic regression analyses indicated that diabetes (OR 3.076, 95%CI 1.442~5.304), smoke (OR 2.745, 95%CI 1.288~4.613), COPD (OR 3.949, 95%CI 1.067~5.733), concurrent chemotherapy (OR 2.072, 95%CI 1.121~3.498), radiotherapy dose ≥ 60 Gy (OR 3.841, 95%CI 1.932~5.362), and PTV ≥ 396 (OR 1.247, 95%CI 1.107~1.746) were the independent risk factors of RILI in patients with NSCLC (all P < 0.05).

CONCLUSIONS

RILI is commonly seen in NSCLS patients; early targeted measures are warranted for patients with those risk factors; future studies with larger sample sizes and different areas are needed to further elucidate the influencing factors of RILI in the treatment of NSCLS.

Imaging of the post-radiation chest in lung cancer

Radiation therapy using conventional fractionated external-beam or high-precision dose techniques including three-dimensional conformal radiotherapy, stereotactic body radiation therapy, intensity-modulated radiation therapy, and proton therapy, is a key component in the treatment of patients with lung cancer. Knowledge of the radiation technique used, radiation treatment plan, expected temporal evolution of radiation-induced lung injury and patient-specific parameters, such as previous radiotherapy, concurrent chemoradiotherapy, and/or immunotherapy, is important in imaging interpretation. This review discusses factors that affect the development and severity of radiation-induced lung injury and its radiological manifestations with emphasis on the differences between conventional radiation and high-precision dose radiotherapy techniques.

Immune Checkpoint Inhibitor-Associated Pneumonitis in Non-Small Cell Lung Cancer: Current Understanding in Characteristics, Diagnosis, and Management

Immunotherapy that includes programmed cell death-1 (PD-1), programmed cell death- ligand 1 (PD-L1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors has revolutionized the therapeutic strategy in multiple malignancies. Although it has achieved significant breakthrough in advanced non-small cell lung cancer patients, immune-related adverse events (irAEs) including checkpoint inhibitor pneumonitis (CIP), are widely reported. As the particularly worrisome and potentially lethal form of irAEs, CIP should be attached more importance. Especially in non-small cell lung cancer (NSCLC) patients, the features of CIP may be more complicated on account of the overlapping respiratory signs compromised by primary tumor following immunotherapy. Herein, we included the previous relevant reports and comprehensively summarized the characteristics, diagnosis, and management of CIP. We also discussed the future direction of optimal steroid therapeutic schedule for patients with CIP in NSCLC based on the current evidence.