Caution: DXd ADC + agents with pneumonitis risk

This caution pairing concerns combining Trastuzumab deruxtecan or Datopotamab deruxtecan with agents that carry their own pneumonitis risk. These DXd ADCs can inflame the lungs, and adding immunotherapy, radiation or mTOR inhibitors stacks that risk through overlapping mechanisms that make the cause hard to attribute, as the Interstitial lung disease (ILD) / pneumonitis entry explains. ILD affects a notable minority of patients on T-DXd, checkpoint inhibitors such as Durvalumab and Pembrolizumab add a further small risk, and trials such as DESTINY-Breast07/08 and TROPION-Breast05 use careful monitoring. The evidence is toxicity data from those trials, and the pairing informs the idea of finding the lowest effective doses in a combination.