A key side effect of the FGFR inhibitor erdafitinib is central serous retinopathy, presenting as blurred vision. Standard of care involves a baseline ophthalmologic exam before starting treatment. If blurred vision occurs, treatment should be held immediately, but the condition is typically reversible and manageable with dose reduction.

Broad-spectrum RAS-on inhibitors like daraxonrasib present skin toxicity as a dose-limiting side effect. However, this rash is clinically distinct from that caused by EGFR inhibitors. It is often manageable with brief treatment interruptions, frequently without requiring dose reductions, and patients tend to acclimate to it over time.

Real-world data for pemigatinib in cholangiocarcinoma showed a higher response rate (59%) than the pivotal FITE-202 trial (36%). This discrepancy likely stems from the lack of standardized, centrally reviewed imaging in real-world settings, which can inflate perceived response. Comparable progression-free survival across both settings supports this interpretation.

New targeted therapies like Zanidatamab and Zolbetuximab show great promise but cause significant side effects like diarrhea and nausea. Their successful clinical adoption hinges on proactive management using detailed guidelines and prophylactic medications, as toxicity can be severe enough to force treatment discontinuation despite the drug's efficacy.

The side effect profile of capivasertib is front-loaded. Key toxicities like diarrhea and rash appear quickly, leading to the majority (63%) of drug discontinuations occurring within the first three months. This highlights a critical window for proactive management and patient education to improve adherence.

Real-world data shows higher rates of cytokine release syndrome (CRS) with tarlatumab than trials reported, especially in sicker patients. Despite this, the drug's risk-benefit profile is often better than chemotherapy for poor-performance patients, sometimes leading to durable, life-changing outcomes where no other options exist.

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.

Despite being advanced targeted therapies, TROP2-directed ADCs present complex safety profiles. Oncologists must manage classic chemotherapy side effects like nausea and cytopenias alongside unique, serious toxicities including stomatitis, ocular issues, and potentially fatal interstitial lung disease, requiring specialized patient monitoring and counseling.

Newer TKI formulations ensure consistent drug absorption, correcting for under-dosing caused by food or other medications. While improving efficacy, this means more patients may experience the drug's known side effects. What seems like new toxicity could be the drug’s true profile, no longer masked by poor absorption.