Oligometastasis is a state in which cancer patients have a limited number of metastatic tumors; patients with oligometastases survive longer than those with polymetastases. Extensive disease (ED)-small cell lung cancer (SCLC) is considered a systemic disease and a poor survival. This study investigated whether the concept of oligometastases is prognostic factor also applicable to patients with ED-SCLC. We performed a retrospective study of 141 consecutive patients with ED-SCLC between 2008 and 2016. The patients were divided into four subgroups: group 1; patients with solitary metastatic site in one organ (n = 31), group 2; patients with 2–5 metastatic sites in one organ (n = 18), group 3; patients with over 6 metastases in one organ (n = 15), and group 4; patients with 2 or more metastatic organs (n = 77). It was identified that 49 patients with ED-SCLC had oligometastases (groups 1 + 2) and 92 had polymetastases (groups 3 + 4). The prognoses of patients with ED-SCLC and oligometastases, defined as ≤5 metastases in a single organ, were significantly superior to those of patients with polymetastases [16.0 (95% CI, 11.0–21.0) months vs. 6.9 (95% CI, 6.0–7.8) months; p<0.001]. 43 of 49 patients with ED-SCLC and oligometastases were relapsed after initial chemotherapy, and 38 (88%) experienced local recurrence. Patients with ED-SCLC and oligometastases may have improved survival than those with polymetastases. As oligometastatic ED-SCLC tends to recur locally, local therapy combined with systemic chemotherapy may be a treatment option.

Background: Small cell lung cancer (SCLC) is typically categorized according to disease extent as limited or extensive, and utility of the 8th TNM classification, recommended for lung cancer staging, which demonstrates a strong association with non-small-cell lung cancer (NSCLC) management, remains unclear. Methods: This retrospective study included 277 consecutive SCLC patients treated at a single institution between 2008 and 2016. Results: According to the currently used two-stage system, 186 (65.7%) of the patients were classified as having extensive disease (ED)-SCLC. Among the ED-SCLC patients, ten (5.3%), 38 (20.4%), 32 (17.2%), and 106 (57.0%) were categorized into stages M0, M1a, M1b, and M1c, respectively, according to the 8th TNM classification. There was a significant difference in overall survival based on the M descriptors: 15.8 (95% CI 9.4–22.2) months in the M1b group vs 7.3 (95% CI 5.7–8.9) months in the M1c group (P<0.001). Multivariate analysis showed that in addition to the known prognostic factors such as performance status, serum albumin, and lactate dehydrogenase, M descriptor was a prognostic factor (HR 1.95, 95% CI 1.38–2.77; P<0.001). Conclusion: The 8th TNM classification has a prognostic value in SCLC. Similarly to NSCLC, treatment approaches should be considered on the basis of the 8th TNM classification, especially stage IVA separate from stage IVB in ED-SCLC patients.

The efficacy of combined modality therapy is evaluated for patients with extensive-stage (ES) small cell lung cancer (SCLC). This study evaluated prognostic factors affecting the risk of thoracic progression in ES-SCLC patients likely to undergo thoracic radiotherapy combined chemotherapy. A retrospective review of ES-SCLC patients who had received systemic chemotherapy at our hospital was performed. Tumor size, metastatic sites, and laboratory data at diagnosis were evaluated as potential prognostic factors. In ES-SCLC patients without pleural dissemination, the rate of thoracic progression after initial chemotherapy was assessed. Eighty-three of 96 consecutive ES-SCLC patients were analyzed. The overall response rate was 55 %, median progression free survival was 5.0 months (mo), and overall survival (OS) was 9.2 mo. Tumor size (19.4 mo for ≤3 cm vs. 8.5 mo for >3 cm, p = 0.017) and the number of metastatic sites (12.9 mo for single sites vs. 7.1 mo for multiple sites, p = 0.015) were prognostic factors, in addition to known prognostic factors such as performance status and the levels of LDH and sodium. Cox proportional hazard model showed that the OS was significantly worse in patients with large (>3 cm) primary tumor size {HR 2.44 [95 % confidential interval (CI) 1.05–5.68], p = 0.038} and multiple metastatic sites [HR 1.81 (95 % CI 1.08–3.04), p = 0.026]. In 51 cases without pleural dissemination, the number of metastatic sites was associated with thoracic progression after initial chemotherapy (65 % for single sites vs. 36 % for multiple sites, p = 0.036). Large tumor size and multiple metastatic sites at diagnosis significantly predicted poor survival in ES-SCLC patients. Based on the high rate of thoracic progression in ES-SCLC patients with single site of distant metastasis, we should consider thoracic radiotherapy combined with chemotherapy for this population.