Thymus Dosimetric and Morphologic Predictors of Radiation-Induced Lymphopenia in Stage III NSCLC

Condition(s) studied

Investigational drug(s) / intervention(s)

Definitive Thoracic Radiotherapy: Patients with stage III non-small cell lung cancer (NSCLC) receive standard-of-care definitive radiotherapy to the chest, with or without concurrent/sequential chemotherapy. Radiotherapy is delivered using conventional fractionation (typically 1.8-2.0 Gy per fraction, total dose 50-66 Gy) or hypofractionated regimens as per institutional protocols. Treatment planning is performed using intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT) For the purposes of this observational study, the radiation dose-volume parameters of the thymus gland (e.g., Dmean, V5Gy, V10Gy, V20Gy) are extracted from each patient's treatment planning system. Morphologic features of the thymus (volume, density, transverse diameter) are measured from planning CT scans.

Definitive Thoracic Radiotherapy: Patients with stage III non-small cell lung cancer (NSCLC) receive standard-of-care definitive radiotherapy to the chest, with or without concurrent/sequential chemotherapy. Radiotherapy is delivered using conventional fractionation (typically 1.8-2.0 Gy per fraction, total dose 50-66 Gy) or hypofractionated regimens as per institutional protocols. Treatment planning is performed using intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT)

Study summary

This study is being done to find out whether features of the thymus gland can predict a common side effect of radiation therapy for lung cancer called radiation-induced lymphopenia.

We will include adults with stage III non-small cell lung cancer (NSCLC) who are scheduled to receive curative radiation therapy to the chest, with or without chemotherapy.

Before, during, and after radiation therapy, we will measure:

The dose of radiation that reaches the thymus gland (based on each patient's treatment plan)

The size and shape of the thymus gland (using CT scans taken for radiation planning)

The number of lymphocytes (a type of immune cell) in routine blood samples

The main goal is to see if certain radiation doses to the thymus, or a smaller thymus size, can predict severe lymphopenia. We will also check whether lymphopenia affects patient outcomes such as infections or survival.

This is an observational study (no added treatment or drug) - patients will receive their standard radiation therapy as planned by their doctor. The study only collects and analyzes data from standard scans and blood tests.

Potential benefits: Findings may help doctors design "immune-sparing" radiation plans in the future to reduce lymphopenia. Potential risks: There are no additional risks beyond standard radiation therapy, as this study does not change your treatment.

Eligibility

Primary outcome measure(s)

• Severe radiation-induced lymphopenia (grade ≥3) — From baseline (within 7 days before radiotherapy initiation) to 6 weeks after completion of radiotherapy.
  Occurrence and severity of radiation-induced lymphopenia during definitive thoracic radiotherapy for stage III non-small cell lung cancer. Lymphopenia is defined based on absolute lymphocyte count (ALC) measured from peripheral blood samples. Severity is graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE), version 5.0: Grade 1: ALC \< lower limit of normal to 800 cells/μL Grade 2: ALC 500 - \<800 cells/μL Grade 3: ALC 200 - \<500 cells/μL Grade 4: ALC \<200 cells/μL The primary analysis will focus on grade ≥3 lymphopenia as the main endpoint. Absolute lymphocyte count nadir (lowest value during treatment) and relative change from baseline are also captured as continuous secondary measures within this outcome.
• radiation-induced lymphopenia — From baseline (within 7 days before radiotherapy initiation) to 6 weeks after completion of radiotherapy. ALC is measured at least weekly during radiotherapy, at the end of radiotherapy, and at 4-6 weeks post-radiotherapy.
  Occurrence and severity of radiation-induced lymphopenia during definitive thoracic radiotherapy for stage III non-small cell lung cancer. Lymphopenia is defined based on absolute lymphocyte count (ALC) measured from peripheral blood samples. Severity is graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE), version 5.0. Grade 1: ALC \< lower limit of normal to 800 cells/μL Grade 2: ALC 500 - \<800 cells/μL Grade 3: ALC 200 - \<500 cells/μL Grade 4: ALC \<200 cells/μL The primary analysis will focus on grade ≥3 lymphopenia as the main endpoint. Absolute lymphocyte count nadir (lowest value during treatment) and relative change from baseline are also captured as continuous secondary measures within this outcome.

Trial sites (1)