TDXD is highly emetogenic. Adding low-dose olanzapine to the standard three-drug antiemetic prophylaxis regimen is a transformative strategy that significantly reduces both acute and delayed nausea, making the potent therapy much more tolerable for patients.

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.

Drawing lessons from T-DXD, experts treat newer exatecan-payload ADCs like RDXD as highly emetogenic from the first dose. Instead of a 'wait and see' approach, they recommend aggressive premedication with a triple-drug antiemetic regimen to prevent nausea and maintain quality of life.

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.

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.

The POTOMAC trial's success adding durvalumab to BCG for non-muscle invasive bladder cancer introduces a major logistical hurdle. Urologists, who typically manage these patients, often lack the expertise to handle systemic immunotherapy side effects, creating uncertainty about which specialty will administer this new standard of care.

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.

For managing nausea from ADCs like TDXD, a three-drug prophylactic regimen (steroid, 5-HT3 antagonist, NK1 inhibitor) is recommended. For delayed nausea, continuing the 5-HT3 antagonist on days two and three is often effective before needing to add agents like olanzapine.

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.