SUMMARY: Lung cancer is the second most common cancer in both men and women and accounts for about 13% of all new cancers and 21% of all cancer deaths. The American Cancer Society estimates that for 2023, about 238,340 new cases of lung cancer will be diagnosed and 127,070 patients will die of the disease. Lung cancer is the leading cause of cancer-related mortality in the United States. Non-Small Cell Lung Cancer (NSCLC) accounts for approximately 85% of all lung cancers. Of the three main subtypes of NSCLC, 30% are Squamous Cell Carcinomas (SCC), 40% are Adenocarcinomas and 10% are Large Cell Carcinomas. With changes in the cigarette composition and decline in tobacco consumption over the past several decades, Adenocarcinoma now is the most frequent histologic subtype of lung cancer.
Immunotherapy with Immune Checkpoint Inhibitors (ICIs) has revolutionized cancer care and has become one of the most effective treatment options, by improving Overall Response Rate and prolongation of survival, across multiple tumor types. These agents target Programmed cell Death protein-1 (PD-1), Programmed cell Death Ligand-1 (PD-L1), Cytotoxic T-Lymphocyte-Associated protein-4 (CTLA-4), and many other important regulators of the immune system. Checkpoint inhibitors unleash the T cells resulting in T cell proliferation, activation, and a therapeutic response. Biomarkers predicting responses to ICIs include Tumor Mutational Burden (TMB), Mismatch Repair (MMR) status, and Programmed cell Death Ligand 1 (PD‐L1) expression. Other biomarkers such as Tumor Infiltrating Lymphocytes (TILs), TIL‐derived Interferon‐γ, Neutrophil‐to‐Lymphocyte ratio, and peripheral cytokines, have also been proposed as predictors of response.
The optimal duration of treatment with ICIs across tumor types is currently unknown and finding the balance between efficacy, toxicity and cost of therapy remains an ongoing challenge. There are presently no adequately powered, prospective, ICI trials, comparing different treatment durations. Even though patients were treated with first line ICI therapy for up to 2 years in key pivotal trials, a significant number of clinicians are hesitant to discontinue ICI therapy and many patients continue therapy beyond 2 years.
The present study was conducted to assess practice patterns surrounding ICI treatment discontinuation at 2 years and to evaluate the association of duration of therapy with Overall Survival, in patients who received Fixed-Duration ICI therapy for 2 years versus those who continued therapy beyond 2 years.
The researchers in this retrospective, population-based cohort study used the longitudinal Flatiron Health database derived from the Electronic Health Record, which included deidentified data of patients originating from approximately 280 cancer clinics (approximately 800 sites of care) throughout the US. The present study cohort included 1091 adult patients (aged at least 18 years) with a new diagnosis of advanced or metastatic NSCLC between 2016 and 2021, who received frontline treatment with Immune Checkpoint Inhibitor (ICI) either alone or in combination with chemotherapy, who were still on ICI treatment at 2 years, and whose cancer had not progressed. Patients with driver mutations in EGFR, ALK, or ROS1 were excluded. Of these patients who initiated treatment with first-line immunotherapy, the researchers focused on 706 patients who completed 2 years of therapy with ICI, of whom 113 patients stopped ICI therapy at 2 years (Fixed-Duration Therapy group) and 593 patients continued ICI therapy beyond 2 years (Indefinite-Duration Therapy group). The median age was 69 years in both treatment groups Patients in the Fixed-Duration group versus the Indefinite-Duration group were more likely to have a history of smoking, respectively and be treated in an academic center. Approximately 50% of patients in both groups were treated initially with immunotherapy alone versus chemoimmunotherapy. The researchers compared the survival between long-term ICI responders whose therapy was discontinued at 2 years in the absence of death or progression (Fixed-Duration group) and those who continued ICI beyond 2 years (Indefinite-Duration group).
With a median follow up of 14.0 months starting 760 days after treatment initiation, there was no statistically significant difference in Overall Survival between patients treated with Fixed-Duration and Indefinite-Duration ICI therapy on either unadjusted or adjusted analysis, and was 79% and 81% respectively. The researchers noted that among patients still on ICI treatment at 2 years, 4 out of 5 patients continued to receive immunotherapy rather than discontinuing it, suggesting that there was a strong bias toward potential overtreatment versus possible undertreatment.
A small cohort of patients in the Fixed-Duration therapy group had disease progression, and was rechallenged with ICI after at least 30 days without treatment. The median time from cessation of frontline treatment to initiation of second-line therapy was 7.4 months. After ICI rechallenge, median Progression Free Survival 2 (PFS2) was 8.1 months.
The authors from this study findings concluded that for patients who are progression-free on Immune Checkpoint Inhibitor therapy for NSCLC, it is a reasonable strategy to stop ICI therapy at 2 years, rather than continuing therapy indefinitely, as there was no statistically significant difference in Overall Survival by Fixed-Duration (2 years) versus Indefinite-Duration (more than 2 years) of ICI therapy.
Association Between Duration of Immunotherapy and Overall Survival in Advanced Non–Small Cell Lung Cancer. Sun L, Bleiberg B, Hwang W-T, et al. JAMA Oncol. Published online June 4, 2023. doi:10.1001/jamaoncol.2023.1891
