Real-world predictors of survival in patients with extensive-stage small-cell lung cancer in Manitoba, Canada: a retrospective cohort study

Background

Extensive-stage small-cell lung cancer (ES-SCLC) is an incurable cancer with poor prognosis in which characteristics predictive of long-term survival are debated. The utility of agents such as immune checkpoint inhibitors highlights the importance of identifying key characteristics and treatment strategies that contribute to long-term survival and could help guide therapeutic decisions.

Objective

This real-world analysis examines the characteristics, treatment patterns, and clinical outcomes of patients receiving chemotherapy without immunotherapy for ES-SCLC in Manitoba, Canada.

Methods

A retrospective cohort study assessed patient characteristics, treatment, and survival duration (short: <6 months; medium: 6-24 months; long: >24 months) using the Manitoba Cancer Registry and CancerCare Manitoba records. Eligible patients were aged >18 years with cytologically confirmed ES-SCLC diagnosed between January 1, 2004, and December 31, 2018, and received cytotoxic chemotherapy (CT). The one-, two-, and five-year probabilities of overall survival (OS) were assessed relative to patient, disease, and treatment characteristics using Kaplan-Meier methods and Cox proportional hazards models.

Results

This analysis included 537 patients. Cisplatin was used in 56.1% of patients, 45.6% received thoracic radiotherapy (RT), and few received prophylactic cranial irradiation (PCI). In the overall cohort, one-, two- and five-year OS rates were 26%, 8%, and 3%, respectively. For patients with Eastern Cooperative Oncology Group Performance Status (ECOG PS) 0, OS rates at one, two, and five years were 43%, 17%, and 10%, respectively, vs. 27%, 8%, and 2% for those with ECOG PS 1-2, and 16%, 3%, and 3% for those with ECOG PS 3-4. In long-term survivors, ECOG PS scores were lower and abnormal laboratory test results were less frequent. Overall, 74.4% of long-term survivors received thoracic RT and 53.5% received PCI. Known poor prognostic factors - including brain/liver metastases, high lactate dehydrogenase (LDH), abnormal sodium, and low hemoglobin levels - were less common but still seen in long-term survivors.

Conclusion

Although rare, patients with ES-SCLC may experience long-term survival with CT ± thoracic RT ± PCI. Factors predicting long-term survival include traditional prognostic factors such as ECOG PS, LDH level, and receipt of thoracic RT or PCI. These findings support current treatment algorithms for ES-SCLC and provide baseline survival estimates to assess the real-world impact of adding immune checkpoint inhibitors in the future.

Chemotherapy or chemo-immunotherapy as first-line treatment for extensive-stage small-cell lung cancer - a meta-analysis

This meta-analysis investigated the clinical benefits of chemo-immunotherapy in extensive-stage small-cell lung cancer (ES-SCLC). Seven randomized controlled trials with a total of 2862 patients were analyzed. Compared with chemotherapy alone, chemo-immunotherapy provided a better progression-free survival (PFS) with a hazard ratio (HR) of 0.81, p < 0.00001, and overall survival (OS) with a HR of 0.82, p < 0.0001; however, the incidence of treatment-related adverse effects (TRAEs) was significantly increased. Subgroup analyses showed that good performance status, cisplatin-based chemotherapy, without brain metastases at baseline and non-Asian populations were associated with greater benefits in OS from chemo-immunotherapy. Chemo-immunotherapy demonstrated better PFS and OS compared with chemotherapy alone as first line treatment in ES-SCLC, but additional TRAEs should be closely monitored.