In a patient with long-term breathlessness and a history of radiotherapy, what is the most likely diagnosis?

In a patient with long-term breathlessness and a history of radiotherapy, the most likely diagnosis is radiation fibrosis. This condition occurs as a result of damage to the lung tissue from radiation exposure during cancer treatment. Radiotherapy can lead to scarring (fibrosis) of the lung parenchyma, which can manifest as progressive breathlessness over time, even years after the treatment. The fibrotic changes can impair lung function and contribute to symptoms similar to those seen in interstitial lung disease.

Radiation fibrosis typically presents with a history consistent with prior radiation therapy, followed by a gradual onset of respiratory symptoms. On imaging, one may observe changes such as reticular opacities and architectural distortion, which are characteristic features of lung fibrosis.

In contrast, other conditions listed have different etiologies and clinical presentations. For instance, bronchiectasis is often associated with chronic infections or inflammatory processes that damage the airways, while chronic aspiration typically presents with recurrent respiratory infections or aspiration pneumonia. Sarcoidosis is a systemic granulomatous disease that, although it can affect the lungs, would typically present with more systemic symptoms or specific imaging findings that may not align with solely a history of radiotherapy. Thus, considering the context of the patient’s background