When CLL patients temporarily stop their BTK inhibitor for a procedure, they can experience a "disease flare" mimicking relapse. It is critical for clinicians to recognize this phenomenon and not misinterpret it as true disease progression, as symptoms typically resolve upon restarting the medication.

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.

A Phase 3 trial revealed that the RET inhibitor pralsetinib causes a higher rate of severe and opportunistic infections than chemotherapy. This suggests significant immunomodulatory effects beyond neutropenia. This surprising safety finding makes selpercatinib the more favorable RET inhibitor for treating NSCLC.

The RET inhibitor selpercatinib can cause a rare side effect of chylous (milky) ascites or pleural effusion. This can be misread on scans as cancer progression, leading to premature discontinuation of an effective drug. Clinicians must tap the fluid before assuming treatment failure, as switching to pralsetinib may resolve the issue.

Combining KRAS G12C inhibitors with checkpoint inhibitors increases the risk of transaminitis. Differentiating the causative agent is clinically challenging. A rapid recovery after stopping both drugs suggests the KRAS inhibitor is the cause and can be restarted at a lower dose; slower recovery points to the immunotherapy.

While both Talatrectinib and Repotrectinib show impressive efficacy in ROS1-positive NSCLC, the choice between them can hinge on their side effect profiles. Talatrectinib demonstrates lower rates of TRK-related adverse events like dizziness, offering a key advantage in clinical practice.

Loncastuximab Tesirine (Lanka-T) can cause a unique "third spacing" side effect, leading to significant edema and fluid retention that is resistant to common diuretics like furosemide (Lasix). Spironolactone has proven more effective for managing this specific toxicity, representing a key clinical pearl for nurses and prescribers.

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.