Defining limited stage small cell lung cancer: a radiation oncologist’s perspective

Small cell lung cancer (SCLC) comprises 13%–15% of all diagnosed lung carcinomas and approximately 30% of those will be defined as limited stage-SCLC (LS-SCLC).1 The definition of LS-SCLC has undergone many modifications and there is no universally accepted definition till date (figure 1).2 It was first defined by the Veteran Affairs Lung cancer study Group (VALG) in 1973 and further redefined by the International Association for the Study of Lung Cancer (IASLC) and American Joint Committee on Cancer (AJCC) in 1989 and 2010, respectively.1 2 Considerable heterogeneity exists pertaining to which definition is used for treating patients in routine practice. As a direct consequence of this, discussions often arise in multidisciplinary tumour board meetings in which different oncologists classify the same patient differently. The subsequent images demonstrate the heterogeneity in subjective classification of patients with SCLC and the role of radiotherapy (RT) in appropriate classification of SCLC. Figure 1 Diagrammatic representation of various anatomical definitions used in defining LS-SCLC. (A) Simplified line diagram depicting the areas of interest within and outside the thoracic cavity. (B) Veteran Affairs Lung cancer study Group, 1973. According to this classification system, LS-SCLC is defined as disease confined to one hemithorax (although local extension may be present) when primary tumour and regional nodes can be encompassed in a radiation port without extrathoracic metastases (except for ipsilateral SCF nodes). The anatomical regions that satisfy this criteria are shown in blue multipronged stars (T, primary tumour; N, nodes) and the encompassing radiation portal is shown in blue dashed line. The anatomical regions that are excluded are shown in red numbered circles (1, contralateral SCF nodes; 2, contralateral hilar nodes; 3, contralateral hilar nodes; 4, contralateral lung nodule; 5, malignant pleural effusion; 6, malignant pericardial effusion). (C) International Association for the Study of Lung Cancer, 1989. According to this classification system, LS-SCLC is defined …