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.

Contrary to initial concerns, long-term safety data for thrombopoietin receptor agonists has allayed fears of malignant transformation and irreversible bone marrow fibrosis. The increased reticulin fibrosis observed is reversible upon drug discontinuation, offering significant reassurance for long-term prescribing.

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.

A patient's time to progression on first-line CDK4/6 inhibitor therapy acts as an informal biomarker. A shorter duration, such as 14 months, is viewed by experts as "not so great" and indicates a degree of underlying endocrine resistance that influences subsequent treatment strategies.

Concerns about bone marrow fibrosis with TPO receptor agonists have been resolved. The effect is a reversible increase in reticulin fibrosis, not the permanent collagen fibrosis seen in myelofibrosis. It resolves upon stopping the drug, so routine bone marrow biopsies for monitoring are unnecessary.

A real-world analysis of pemigatinib reported low rates of dose reduction or discontinuation. This may be misleading, as the toxicities of FGFR inhibitors (e.g., nail, skin, eye issues) are cumulative and worsen over extended periods. The study's shorter follow-up likely didn't capture the full long-term safety profile of the drug.

Using capivasertib in the hormone-sensitive setting is preferred because the cancer is more likely dependent on the AKT pathway for growth. In later, castration-resistant stages, additional genetic alterations can emerge, creating redundant growth signals and potentially diminishing the inhibitor's efficacy.

Clinicians must counsel patients that some drug toxicities are irreversible or create lifelong conditions. Alopecia from hedgehog inhibitors can be permanent, while immunotherapy-induced adrenal insufficiency or Type 1 diabetes require daily management, a significant quality-of-life burden for older patients.

Recurrent non-melanoma skin cancers in patients on ruxolitinib may be attributable to its JAK1 inhibition. In such cases, a viable strategy is to switch the patient to a more JAK2-selective inhibitor, such as pacritinib or fedratinib, to potentially mitigate this specific side effect while maintaining disease control.