New Tumor Type May Help Identify High-Risk Small Cell Lung Cancer

Researchers have identified a new tumor state in small cell lung cancer (SCLC) that may help explain why some patients have poorer outcomes following treatment with chemotherapy and immunotherapy, according to a study published in Cell Reports Medicine.

The newly identified state, called SCLC-SL, was associated with shorter survival among patients with extensive-stage small cell lung cancer, meaning the disease has spread beyond one side of the chest.

In an analysis of patients treated with chemotherapy and immunotherapy, those whose tumors showed the stem-like state had a median overall survival of 7.41 months, compared with 15.9 months for patients with an immune-active tumor state and 12.6 months for those with a neuroendocrine tumor state.

Median overall survival refers to the length of time at which half of the patients in a group were still alive.

The findings could eventually help doctors identify patients who may be less likely to benefit from current treatments and who might need alternative approaches. However, more research is needed before the tumor classification can be used to guide treatment decisions.

How Does the Newly Identified Tumor State Affect Survival?

Small cell lung cancer is an aggressive form of lung cancer that often grows and spreads quickly. Although combining chemotherapy with immunotherapy has improved treatment options, the disease frequently returns or progresses after treatment.

Researchers have struggled to identify which patients are most likely to experience poor outcomes.

In the study, investigators examined data from 132 patients who participated in the phase 3 IMpower133 trial and received Tecentriq (atezolizumab), an immunotherapy drug, alongside the chemotherapy drugs carboplatin and etoposide.

The analysis identified three major tumor states:

• Stem-like (SCLC-SL): Cancer cells that are less specialized and appear better able to adapt to stress and changing conditions.
• Immune-active: Tumors that show greater activity in genes involved in immune responses.
• Neuroendocrine: Tumors that show characteristics associated with nerve cells and hormone-producing cells.

Patients whose tumors showed the stem-like state had the shortest median overall survival of the three groups.

The researchers also found that the association between SCLC-SL and shorter survival remained significant after accounting for other factors linked to poor outcomes, including cancer that had spread to the liver or brain and elevated levels of lactate dehydrogenase (LDH), a substance measured in the blood that can be associated with disease activity.

"To our knowledge, this is one of the first studies to show that a SCLC molecular feature has independent prognostic significance after accounting for established clinical risk factors, including liver and brain metastases and serum levels of LDH," Dr. Anish Thomas, senior author of the study and professor of hematology and oncology at Northwestern University Feinberg School of Medicine, said in a news release.

This suggests that the tumor state may provide information about a patient's prognosis beyond the factors doctors already use to assess their disease.

Why Might Some Small Cell Lung Cancers Stop Responding to Treatment?

Researchers found that the SCLC-SL state had characteristics that may help explain why some tumors become resistant to treatment.

Unlike other tumor states, SCLC-SL showed lower levels of immune-related activity and greater activity in processes that help cancer cells produce energy, survive stress and adapt to changing conditions.

To better understand these differences, researchers examined how DNA is packaged inside cancer cells, which affects which genes the cells can turn on or off. They then compared their findings with gene activity data from more than 800 tumors across multiple groups of patients.

The researchers also studied tumor samples collected from the same patients at different points during treatment.

Among 31 paired samples, the proportion classified as SCLC-SL increased from approximately 33% before or earlier in treatment to 58% in later samples.

This suggests that some tumors may shift toward the stem-like state following treatment, potentially allowing cancer cells to survive and continue growing.

"This shifts the way we think about SCLC subtypes," Thomas said. "Rather than viewing tumors as belonging to fixed categories, our data suggest that SCLC can occupy different regulatory states and potentially transition between them."

The findings suggest that small cell lung cancer may change over time rather than remaining biologically the same throughout treatment.

However, researchers have not established whether these changes directly cause treatment resistance.

Could the New Tumor State Lead to Better Treatments?

Identifying the stem-like tumor state could help researchers develop treatments for patients whose cancers are less responsive to current therapies.

Because SCLC-SL tumors showed greater activity in pathways involved in energy production and stress responses, researchers believe these processes could offer potential targets for future treatments.

The study also found that SCLC-SL tumors had lower levels of certain proteins targeted by some emerging cancer therapies, suggesting that treatments designed for other small cell lung cancer tumor types may not work equally well against this group.

However, the study did not test new treatments against SCLC-SL tumors or demonstrate that targeting these biological pathways would improve survival.

The findings are based on laboratory research and analyses of existing patient data. Further studies are needed to confirm whether the tumor state can reliably predict treatment outcomes and whether it can be targeted with new therapies.

What Do These Findings Mean for Patients With Small Cell Lung Cancer?

For patients with small cell lung cancer, the research could eventually lead to more personalized treatment decisions.

If a test can reliably identify the SCLC-SL state before treatment begins, doctors may be better able to recognize patients who face a greater risk of poor outcomes with existing therapies.

Those patients could potentially be considered for clinical trials evaluating alternative treatment strategies.

"If validated prospectively, a chromatin-informed signature could help identify patients whose tumors have this high-risk stem-like biology and who may be less likely to benefit from current approaches alone," Thomas said. "It could also help direct these patients toward clinical trials testing alternative strategies."

For now, the findings do not change standard treatment recommendations. There is not yet a validated clinical test for SCLC-SL that doctors can routinely use to select treatments, and the study does not establish that patients with this tumor state should receive different therapy.

The survival figures also describe outcomes across groups of patients rather than predicting how long any individual patient will live.

Researchers plan to investigate what causes small cell lung cancer cells to develop the stem-like characteristics and whether those changes can be prevented or reversed.

Their next steps also include confirming whether the tumor state can reliably identify patients at higher risk of poor outcomes before treatment begins.

References

1. Kumar R, et al. A stem-like chromatin program in small-cell lung cancer is associated with poor outcomes after chemoimmunotherapy. Cell Reports Medicine. Published online September 10, 2026. doi:10.1016/j.xcrm.2026.103027. https://doi.org/10.1016/j.xcrm.2026.103027
2. Northwestern University Feinberg School of Medicine. New Tumor State Helps Identify High-Risk Small-Cell Lung Cancer. Published October 12, 2026.

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