What Is Cancer-Associated Interstitial Lung Disease?

Why Does It Matter?

Cancer-Associated Interstitial Lung Disease (CA-ILD)is a high-risk diagnostic and treatment scenario involving coexisting interstitial lung disease (ILD) and lung cancer (LC). ILD increases the risks of acute exacerbation (AE-ILD) and drug-induced pneumonitis during surgery, radiotherapy, and systemic treatment, directly affecting survival and treatment decisions. The clinical goal is simultaneous tumor control and protection of the fibrotic lung.

 Definition and Classification of Interstitial Lung Diseases (ILDs)

Interstitial Lung Diseases (ILDs) are a highly heterogeneous group of diffuse pulmonary parenchymal diseases with high morbidity and mortality. Respiratory failure during Acute Exacerbations (AEs) often requires advanced support in Intensive Care Units (ICUs), complicating clinical management.

An important ILD subgroup, Idiopathic Interstitial Pneumonias (IIPs), is divided in updated classifications into three main categories: major, rare, and unclassifiable. This facilitates treatment strategies based on disease behavior , such as fibrotic progression or inflammatory activity. Idiopathic Pulmonary Fibrosis (IPF) is the deadliest subtype and often follows an unpredictably progressive course.

For IIP diagnosis, Multidisciplinary Discussion (MDT)is the ‘gold standard,’ achieving clinician–radiologist–pathologist consensus. In CA-ILD, early diagnosis and accurate stratification are critical for access to suitable trials and individualized management.

Development and Importance of the Cancer-Associated ILD (CA-ILD) Concept

CA-ILD is simultaneous or sequential coexistence of ILD and LC, representing more than comorbidity: it is a distinct phenotype determining toxicity and prognosis. Shared environmental risks (smoking, dust/chemicals) and overlapping molecular pathwaysbetween fibrogenesis and carcinogenesis form its biological basis. Integrated radiological and clinical assessment is essential for diagnosis.

Epidemiology, Risk Factors, and Prognosis

The risk of LC in ILD is approximately 3.5–7.3 times higher than in the general population; 10–20%of people with ILD may develop LC during their lifetime. The most common shared factors are smoking, environmental dust/chemical exposure, and genetic susceptibility. ILD worsens LC prognosis; AE-ILD risk after surgery/immunotherapy is considerable.

Molecular and Cellular Foundations

Epithelial–mesenchymal transition (EMT), reactive oxygen species (ROS), growth factors, and inflammatory and angiogenic mediators are shared mechanismsdriving both fibrogenesis and cancer progression. The wound-like microenvironmentin fibrotic tissue may facilitate tumor development. In chemotherapy-associated AE-ILD, ROS/cytokine-mediated inflammation contributes alongside cytotoxicity.

Cancer Location and Microenvironment

Primary lung cancers frequently arise within or adjacent to existing fibrotic regions, most often in peripheral–basal locations. This supports biological interaction between the fibrotic background and tumor behavior. Eligibility for certain targeted therapies may be limited in CA-ILD; biological differences influence clinical strategies.

Clinical Findings and Diagnostic Approach

Signs and Symptoms

Progressive dyspnea and chronic cough are common; early LC symptoms may be attributed to fibrosis, delaying diagnosis.

High-Resolution CT (HRCT) and Pattern Identification

HRCT is central to diagnosis and risk stratification. Patterns predict AE-ILD risk. Interstitial Lung Abnormalities (ILA) are a strong pretreatment radiological marker of pneumonitis/AE risk.

The Role and Risks of Invasive Methods

BAL may help in differential diagnosis; however, transbronchial/surgical biopsies may increase AE-ILD riskand should be performed only following an MDT decision if they will change management.

Treatment-Related Toxicities and Management Challenges

The lack of large Phase III RCTs complicates CA-ILD management; a delicate risk–benefit balance between anticancer benefit and life-threatening pulmonary toxicity is required.

Management of Acute Exacerbations (AE-ILD) and Supportive Therapies

An acute exacerbation (AE-ILD)can develop in IPF or other non-IPF ILDs, often causing critical hypoxemia requiring advanced ICU respiratory support. High mortality calls for an aggressive, protocol-based approach.

Pharmacological and Nonpharmacological Management

• Corticosteroids: The pharmacological cornerstone of AE-ILD. They are essential in IPF; high-dose steroids may also help non-IPF ILD with evidence of inflammation. Immunosuppressants may be added if inflammation is pronounced.
• Supportive care: High-flow nasal cannula (HFNC) oxygen for severe hypoxemia; noninvasive ventilation (NIV) may be considered with worsening hypoxemia/hypercapnia.

Critical Care Strategies in the ICU

• Ventilation: A low-tidal-volume ‘lung-protective’ strategy; careful PEEP titration; prone positioning in selected cases.
• ECMO & Transplantation: Extracorporeal membrane oxygenation (ECMO) is a rescue option only in refractory cases. Under appropriate conditions, lung transplantation may be considered in end-stage ILD, even in ICU patients.

Future Perspectives and New Treatment Strategies

The Potential of Antifibrotic Therapies in CA-ILD

The potential of antifibrotic therapiesthat slow ILD progression to prevent cancer treatment-related pulmonary toxicity is attracting attention. Nintedanib (a triple kinase inhibitor) is licensed for pulmonary fibrosis and certain LC subtypes (particularly adenocarcinoma). By targeting shared molecular pathways (e.g., EMT), it may reduce fibrotic progression and AE risk while offering antitumor activity in CA-ILD. However, its effects on toxicity prevention and survival require clarification in prospective studies.

Biomarkers and Personalized Medicine Approaches

For early diagnosis, response prediction, and treatment selection, new diagnostic modalities/biomarkers must be developed. Biomarkers matter for predicting disease course and improving trial designs through grouping patients with similar clinical features.

Research Needs

In a complex condition such as CA-ILD, current evidence largely comes from retrospective studies. The role of antifibrotics and the safety of different oncology regimens require large Phase III randomized controlled trials providing prospective evaluation . These trials should include not only overall survival but also AE-ILD incidence as a primary endpoint.

Conclusion and Clinical Practice Recommendations

CA-ILD is a critical clinical challenge characterized by high mortality risk, complex diagnostic requirements, and oncology treatment-related toxicity. Optimal management must go beyond tumor control to stabilize the underlying fibrotic disease and ensure aggressive prevention of treatment-induced pulmonary injury.

Clinical Practice Recommendations

• Multidisciplinary Management: Diagnostic and treatment decisions for every CA-ILD case should be made by an MDT including pulmonology, oncology, radiology, and, when needed, pathology specialists.
• Pretreatment Risk Stratification: Before oncology treatment begins, especially those with a smoking history among high-risk patients should undergo High-Resolution CT (HRCT) screening to detect Interstitial Lung Abnormalities (ILA) or ILD if present.
• Individualized Treatment Selection: All oncology interventions, including surgery, radiotherapy, chemotherapy, and particularly immunotherapy, should be selected based on individualized analysis of high AE-ILD and pneumonitis risk and a safety-focused risk–benefit assessment. Prioritizing limited surgical resection reflects the critical importance of lung preservation in these patients.
• Standard Acute Exacerbation Protocol: AE-ILD treatment should begin with corticosteroids ; ICU care should use low tidal volumes, careful PEEP titration and appropriate support (HFNC, etc.).
• Future Research Priority: The role of antifibrotic agents, particularly Nintedanib, in preventing cancer treatment-related pulmonary toxicity and improving survival in CA-ILD must be clarified through prospective Phase III trials. This would enable safe, effective standard guidelines to be developed.

📚 Sources

• ERS — Interstitial Lung Disease 
• MDPI — The Management of ILD in the ICU 
• PMC — Lung cancer and interstitial lung disease: literature review 
• MDPI — Lung Cancer and Interstitial Lung Diseases 
• AnnalsATS — ILD epidemiology 
• Frontiers Oncology