What are the required Forced Expiratory Volume in 1 second (FEV1) and Diffusing Capacity of the Lung for Carbon Monoxide (DLCO) values for patients undergoing radical radiotherapy for lung cancer?

From the Guidelines

For patients undergoing radical radiotherapy for lung cancer, the generally accepted minimum pulmonary function values are an FEV1 of at least 1.0 liter (or >40% of predicted value) and a DLCO of at least 40% of predicted value. These thresholds help ensure patients have adequate respiratory reserve to tolerate the potential pulmonary toxicity from radiation therapy. However, these values should not be used as absolute cutoffs, as treatment decisions should be individualized. Patients with borderline pulmonary function may still be candidates for radical radiotherapy if using advanced techniques like stereotactic body radiation therapy (SBRT) or intensity-modulated radiation therapy (IMRT), which can minimize radiation exposure to healthy lung tissue. Additional considerations include the patient's performance status, comorbidities, extent of disease, and the volume of lung that will receive radiation. Pulmonary function testing should be complemented by a thorough clinical assessment, and in some cases, split lung function tests or exercise testing may provide additional valuable information for borderline cases 1.

Some studies have suggested that the predicted tolerance for high-dose RT is less well defined and it is, in general, impossible to accurately determine the related acute and long-term risks 1. However, the dose to the heart should be minimized during RT planning to reduce the risk of cardiac toxicity 1. The European Organisation for Research and Treatment of Cancer recommends that patients with a WHO performance score of 2 or worse, or those older than 70 years, should be carefully evaluated before undergoing radical radiotherapy 1.

In terms of specific values, a study published in the Annals of Oncology in 2017 recommended that patients with a predicted postoperative FEV1 and DLCO > 40% are generally considered acceptable for surgical resection, but this may not directly apply to radical radiotherapy 1. Another study published in Chest in 2013 suggested that patients with a PPO FEV1 and PPO DLCO < 30% predicted may still undergo surgery with an acceptable clinical outcome, provided they demonstrate an acceptable exercise capacity 1.

It's worth noting that the evidence is not very strong or equivocal and mixed, and more prospective data are warranted on the toxicity and outcome of chemoradiotherapy in patients with lung cancer 1. Therefore, treatment decisions should be made on a case-by-case basis, taking into account the individual patient's characteristics and the potential benefits and risks of radical radiotherapy.

Key considerations for radical radiotherapy include:

• Patient's performance status
• Comorbidities
• Extent of disease
• Volume of lung that will receive radiation
• Pulmonary function testing, including FEV1 and DLCO
• Split lung function tests or exercise testing for borderline cases
• Minimizing radiation exposure to healthy lung tissue using advanced techniques like SBRT or IMRT.

From the Research

Required FEV1 and DLCO Values for Radical Radiotherapy

• The required Forced Expiratory Volume in 1 second (FEV1) and Diffusing Capacity of the Lung for Carbon Monoxide (DLCO) values for patients undergoing radical radiotherapy for lung cancer are not explicitly stated in the provided studies.
• However, the studies suggest that patients with FEV1 or DLCO < 60% before radiotherapy did not show significant changes after radiotherapy 2.
• A study found that patients with a V20total lung < 21% are at a low risk for pulmonary function decrease after high-dose irradiation treatment, with a median FEV1 relative to baseline of 0.95 and a relative median DLCO of 0.98 at six months 3.
• Another study found that the correlation between V20total lung and FEV1 decline was statistically significant, and that small differences in lung function may be clinically important for patients with chronic obstructive pulmonary disease (COPD) 3.
• The dynamics of DLCO were found to correlate with CT morphology changes in the mid-dose range, especially for the volume of the lungs receiving between 65% and 45% of the dose prescribed (V65−45%) 4.

Factors Affecting FEV1 and DLCO Values

• The studies suggest that the dose-volume effects of accelerated high-dose radiation on pulmonary function are significant, with a correlation between V20total lung and FEV1 decline 3.
• The use of intensity-modulated radiotherapy (IMRT) and dose-differentiated accelerated radiotherapy (DART) may help to minimize the decrease in pulmonary function after radiotherapy 3.
• Simultaneous pulmonary rehabilitation (PR) during thoracic radiotherapy may improve pulmonary function, particularly in measures of FEV1, and exercise capacity for patients with lung or esophageal cancer 5.
• The sum of predicted radiation therapy-induced changes in regional perfusion is related to radiation-induced changes in pulmonary function, although the correlation coefficients are small 6.