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.

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.

Interstitial Lung Disease (ILD) is a significant risk with TDXD. However, a history of a completely resolved grade 1 event does not automatically preclude a patient from receiving the drug again. Clinicians may consider a re-challenge, balancing the risk against the lack of other viable therapies.

High rates of interstitial lung disease (ILD) in TDXD trials for brain metastases might be partly attributable to opportunistic infections like PJP, not direct drug toxicity. This occurs in patients receiving steroids for brain edema, underscoring the need for PJP prophylaxis.

While a small risk of fatal toxicity like interstitial lung disease (ILD) from T-DXd is often accepted in metastatic disease, it's a major concern in the early-stage, curative setting. The ethical bar for safety is much higher when the goal is to cure, making oncologists more cautious about adoption despite efficacy.

To mitigate long-term toxicity from TDXD, oncologists are proposing an "induction/maintenance" approach. Patients receive TDXD for an initial period to achieve maximal response, then switch to a less toxic maintenance regimen for a "chemotherapy holiday," improving quality of life.

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.