Surveillance imaging following definitive radiotherapy for non–small cell lung cancer: What is the clinical impact?

abstract

Lung cancer is the leading cause of cancer death worldwide. Recurrence rates at all stages are high, but evidence-based post-treatment surveillance imaging strategies to detect recurrence are poorly defined, and salvage options are frequently limited. A number of national and international oncology guidelines address post-treatment imaging, but are largely based on low-level, retrospective evidence because of a paucity of high-quality data, particularly in regard to cost-effectiveness and quality-of-life endpoints. Given the lack of randomized data addressing appropriate surveillance imaging modality and interval following definitive treatment of lung cancer, there remains an unmet clinical need. Meaningful surveillance endpoints should include the financial impact, patient quality-of-life outcomes, and access-to-care issues associated with intensive follow-up to ensure that guidelines reflect quality and sustainability. A need for prospective randomized data on the subject of imaging surveillance after definitive local therapy remains an unmet need, and an opportunity for collaboration and further research.

Introduction

Worldwide, with an estimated 1.6 million deaths in 2012, lung cancer is the leading cause of cancer death in men and the second leading cause in women [1], and is the leading cause of cancer death in the United States for both men and women [2]. Non–small cell lung cancers (NSCLC) represent the vast majority of lung cancer cases, accounting for 85% of new lung cancer diagnoses [3]. Surgery is the preferred definitive treatment approach for medically fit, early stage NSCLC patients, and for select locally advanced patients with low-volume disease and good performance status. Definitive radiation or chemoradiation is used for medically inoperable, early stage NSCLC and for locally advanced disease not amenable to resection. At all stages of disease, recurrence rates are high, with a predominantly distant pattern of failure (Figure 1). Limited data address the optimal post-treatment surveillance approach, and most existing studies address post-operative, rather than post-radiation follow-up.

Surveillance imaging with computed tomography (CT) following thoracic radiation is often a challenge to interpret because high doses of radiation often cause extensive local fibrosis that may obscure or mimic local tumor recurrence [4], potentially resulting in additional and potentially unnecessary or dangerous medical procedures. Positron emission tomography (PET) can clarify equivocal CT findings for some patients [5], but post-radiation inflammation can cause increased fludeoxyglucose (FDG) avidity, particularly in the first 6 months post-treatment [6], and the appropriate integration of PET into surveillance algorithms is poorly defined. Salvage options for recurrent lung cancer are often limited because the predominant failure pattern for NSCLC remains distant [7], [8], [9] (Figure 1). However, rates of second primary lung cancers (SPLC) may be as high as 1% to 2% per year [10], and may be amenable to stereotactic body radiotherapy radiation (SBRT) or other local therapies. Herein we review the available data pertaining to surveillance imaging after definitive treatment of NSCLC, with a focus on the post-radiation setting, and discuss the clinical impact on survival, subsequent interventions, cost, and quality of life.