Trastuzumab deruxtecan (TDXD) and datopotamab deruxtecan (Dato-DXd) share the same cytotoxic payload, yet Dato-DXd has a much lower rate of interstitial lung disease (ILD). This indicates the toxicity is driven by the antibody-antigen interaction, not the payload itself.

Due to cumulative toxicity concerns with TDXD, particularly ILD, clinicians express more comfort with the shorter 4-cycle neoadjuvant course from DESTINY-Breast11 than the prolonged 14-cycle adjuvant therapy in DESTINY-Breast05, favoring front-loading the treatment.

Contrary to the belief that any interstitial lung disease (ILD) requires permanent discontinuation of TDXD, data shows patients with asymptomatic, radiographically-identified Grade 1 ILD can be safely rechallenged. Treatment is paused and the patient is treated, but therapy can resume once resolved. Symptomatic ILD, however, requires permanent discontinuation.

For urothelial cancer patients treated with trastuzumab deruxtecan (TDXD), developing symptomatic (Grade 2) interstitial lung disease or pneumonitis is a critical event. Following protocols from other cancers, this requires permanent discontinuation of the therapy. Re-challenging the patient with TDXD after a Grade 2 event is not recommended without more disease-specific safety data.

To manage the risk of interstitial lung disease (ILD) with TDXD, experts now recommend routine screening with high-resolution chest CT scans every 6-12 weeks. This practice aims to catch asymptomatic, grade 1 ILD early, allowing for treatment holds and steroid intervention, which may preserve the option to rechallenge.

Unlike some immunotherapy guidelines, experts recommend immediate steroid treatment for even Grade 1 (asymptomatic) ADC-induced pneumonitis or interstitial lung disease (ILD) found on scans. This aggressive, proactive approach is considered necessary due to the risk of rapid clinical deterioration, prioritizing safety and the ability to resume cancer therapy.

Adopting T-DXd in early-stage breast cancer requires frequent chest CT scans to monitor for potentially fatal interstitial lung disease (ILD), a practice not standard for current therapies. This presents significant new logistical challenges, including securing insurance approvals, managing patient access, and increasing the overall burden of care.

Contrary to initial fears, both clinical trial and real-world data show that patients experiencing asymptomatic, grade 1 interstitial lung disease (ILD) from TDXD can be safely retreated. This allows patients to continue benefiting from a highly effective therapy without undue risk.

While oncologists focus on the low 4% rate of Interstitial Lung Disease (ILD) from neoadjuvant TDXD, surgeons worry this complication could prevent patients from reaching potentially curative surgery, drawing parallels to issues seen with neoadjuvant immunotherapy.