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

David E Dawe; Rebekah Rittberg; Iqra Syed; Mary Kate Shanahan; Daniel Moldaver; Oliver Bucher; Katie Galloway; Kayla Reynolds; James T Paul; Craig Harlos; Julian O Kim; Shantanu Banerji

doi:10.3389/fonc.2023.1191855

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

Front Oncol. 2023 Sep 18:13:1191855. doi: 10.3389/fonc.2023.1191855. eCollection 2023.

Authors

David E Dawe^{1

2

3}, Rebekah Rittberg^{1

2}, Iqra Syed⁴, Mary Kate Shanahan⁴, Daniel Moldaver⁴, Oliver Bucher⁵, Katie Galloway⁵, Kayla Reynolds⁶, James T Paul^{1

2}, Craig Harlos^{1

2}, Julian O Kim^{7

8}, Shantanu Banerji^{1

2

3}

Affiliations

¹ Department of Internal Medicine, University of Manitoba, Winnipeg, MB, Canada.
² Department of Hematology and Medical Oncology, CancerCare Manitoba, Winnipeg, MB, Canada.
³ CancerCare Manitoba Research Institute, CancerCare Manitoba, Winnipeg, MB, Canada.
⁴ AstraZeneca Canada, Mississauga, ON, Canada.
⁵ Department of Epidemiology and Cancer Registry, CancerCare Manitoba, Winnipeg, MB, Canada.
⁶ Department of Cellular & Physiological Sciences, University of British Columbia, Vancouver, BC, Canada.
⁷ Department of Radiology, University of Manitoba, Winnipeg, MB, Canada.
⁸ Department of Radiation Oncology, CancerCare Manitoba, Winnipeg, MB, Canada.

Abstract

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.

Keywords: extensive stage (ES); long-term survival; overall survival (OS); performance status (ECOG-PS); radiotherapy (RT); real world; small cell lung cancer (SCLC).