Purpose Identifying patient characteristics that define a worse disease prognosis or “high tumor burden” (HTB) status is essential for clinical decision-making and treatment selection in metastatic non-small cell lung cancer (mNSCLC). We aimed to define this concept based on the experience of oncologists in clinical practice. Patients and Methods A representative sample of Spanish experts was selected and asked to complete an online survey regarding the definition of HTB according to their personal experience. Results HTB was identified by the oncologists (N = 81) as one of the principle factors influencing first-line treatment decision-making. According to the experts, HTB is mainly defined by the number of metastatic lesions (n = 45, 56%), location (n = 34, 42%), tumor size (sum of diameters of target lesions; n = 26, 32%) and liver involvement (n = 24, 30). High lactate dehydrogenase (LDH) levels were also associated with HTB. Almost half of respondents (n = 33, 41%) believed that one metastatic lesion was sufficient to consider a patient as presenting HTB, 72% (n = 58) considered that two were necessary and 99% (n = 80) three. Liver (n = 76, 100%) followed by brain (n = 65, 86%) were the main metastatic sites associated with HTB. Tumor size ranging from 6 cm to 10 cm as well as high LDH levels (three times the upper limit) defined the concept for 82% (n = 62) and 100% (n = 76) of oncologists, respectively. Conclusion In the real-world setting, according to experts, HTB is defined by the number of metastatic lesions, location of metastases, tumor size and by high LDH levels. Given the relevance of this concept, efforts should be made to unify its definition and to further explore its potential as a prognostic factor for mNSCLC patients.

However, their impact on survival and clinical response in patients with advanced NSCLC undergoing immune checkpoint inhibitor (ICI) treatment has been scarcely investigated. Methods: We retrospectively reviewed 294 patients who underwent ICI therapy for advanced or recurrent non-small-cell lung cancer (NSCLC) between January 2016 and July 2019. Results: Of these 294 patients, 284 (96.6%) had at least one measurable lesion. Of these, 263 patients treated with ICI monotherapy were included in the analysis. The median total and maximum target lesion diameters were 96.5 mm and 49.1 mm, respectively. Median progression-free survival (PFS) with massive lesions (max BTS > 50 mm, group A) and without massive lesions (max BTS 50 mm, group B) was 2.5 months (95% CI 1.8e3.7) and 6.7 months (95% CI 5.1e9.7), respectively. Median overall survival (OS) for groups A and B was 9.5 months (95% CI 5.5e12.3) and 20.0 months (95% CI 13.3e32.0), respectively. The multivariate analysis revealed marked associations between the presence of massive lesions and both PFS and OS. Conclusion: The presence of massive lesions (max diameters > 50 mm) is an independent prognostic factor in advanced NSCLC treated with ICI monotherapy. Although overall response rates were similar between groups A and B, the disease control rate was significantly poorer for group A. Max BTS might be useful for predicting clinical outcomes for patients undergoing immunotherapy as a parameter reflecting their tumor burden.

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