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CE / CME
Management of a Patient With EGFR-Mutated NSCLC and Progression on First-line Osimertinib
Physician Assistants/Physician Associates: 0.50 AAPA Category 1 CME credit
Pharmacists: 0.50 contact hour (0.05 CEUs)
Physicians: maximum of 0.50 AMA PRA Category 1 Credit™
Nurse Practitioners/Nurses: 0.50 Nursing contact hour
Released: April 17, 2026
Expiration: October 16, 2026
Activity
Case Conclusion
After initiation of Dato-DXd, the patient developed grade 1 stomatitis that improved with intensified topical supportive care, including increased frequency of steroid-containing mouthwash and reinforcement of oral hygiene measures, and did not require treatment interruption. She continues therapy with ongoing disease control on follow-up imaging.
Key Research and Case Summary
Reassessing Disease Biology at Progression on EGFR TKIs
This patient first developed a solitary liver lesion after a durable response to first-line osimertinib, while all other disease sites, including the CNS, remained controlled. In patients like this, tissue rebiopsy is important when feasible to confirm recurrent disease, assess for histologic transformation, and evaluate for acquired resistance mechanisms that may alter treatment planning. When progression is limited to a small number of sites, local therapy can be used to control resistant disease while preserving benefit from osimertinib.1
Despite guideline recommendations, rebiopsy rates at TKI progression remain suboptimal in real-world practice.1,2 Barriers include procedural accessibility, patient fitness, and healthcare professional unfamiliarity with the range of resistance mechanisms that tissue analysis can reveal. When tissue biopsy is not feasible, plasma ctDNA testing can complement molecular evaluation; however, ctDNA cannot detect histologic transformation and should not replace tissue when transformation is clinically suspected (eg, onset of neuroendocrine features or rapid clinical deterioration).1,3 A comprehensive rebiopsy strategy also informs eligibility for clinical trials and emerging targeted approaches. For example, patients with concurrent MET amplification, RAS alterations, or mutations in other identified resistance drivers may be candidates for combination strategies rather than empiric chemotherapy or an antibody–drug conjugate alone.1,4
Limited‑Site Progression: Preserve Benefit From Osimertinib When Appropriate
For patients like ours receiving osimertinib with otherwise controlled disease and a single progressing lesion, expert consensus pathways include a local approach (eg, surgery, stereotactic body radiation therapy, ablation) with continuation of osimertinib, provided the patient is clinically stable and there is no widespread systemic progression. This strategy is commonly used to prolong the period of benefit from a well‑tolerated, CNS‑active TKI.1
First Systemic Progression Without a New Actionable Target: Platinum Chemotherapy and the Role of Continuing Osimertinib
When progression becomes systemic and no new targetable resistance alteration is identified, platinum‑based chemotherapy remains a key standard option. This was the situation for the patient in this case after local therapy to her isolated liver lesion: She later developed multifocal extracranial progression with new bilateral pulmonary nodules and enlarging mediastinal lymph nodes, while her brain MRI remained stable. Historically, continuing the prior EGFR TKI with chemotherapy at progression was controversial, but more recent prospective data support a role for maintaining osimertinib as a backbone in selected patients, particularly those with CNS considerations.
In the randomized, double‑blind COMPEL trial (NCT04765059) that enrolled patients with non‑CNS progression on first‑line osimertinib, continuing osimertinib with platinum/pemetrexed improved median progression-free survival compared with placebo plus chemotherapy (8.4 vs 4.4 months; HR: 0.43; 95% CI: 0.27-0.70), with a numerically longer overall survival (15.9 vs 9.8 months; HR: 0.71; 95% CI: 0.42-1.23).5
TROP2 Antibody–Drug Conjugate Integration in EGFR‑Mutated NSCLC: Dato-DXd
Several months after treatment with carboplatin plus pemetrexed and while receiving maintenance therapy with pemetrexed and osimertinib, the patient experienced renewed systemic progression with stable brain imaging, prompting consideration of next-line therapy.
At this point, the patient and her oncologist decided that Dato-DXd would be her next line of therapy. Dato-DXd is a TROP2-directed antibody–drug conjugate with a topoisomerase I inhibitor payload (DXd). In the United States, Dato-DXd received FDA accelerated approval (June 23, 2025) for adults with locally advanced or metastatic EGFR-mutated NSCLC who have received prior EGFR-directed therapy and platinum-based chemotherapy.6,7
Efficacy for this indication was established based on a pooled subgroup analysis of patients with EGFR-mutated NSCLC enrolled on phase II TROPION-Lung05 and phase III TROPION-Lung01. In this pooled analysis of 114 patients, the confirmed overall response rate was 45%, with a median duration of response of 7.0 months and a median progression-free survival of 5.8 months.6,8
Practical Toxicity Management for Dato-DXd
Our patient experienced grade 1 stomatitis on her treatment, highlighting one of the most common adverse events associated with Dato-DXd. In the pooled safety population (TROPION-Lung05, TROPION-Lung01, and TROPION-PanTumor01), stomatitis occurred in 63% of patients, including grade 3 events in 8% and 1 grade 4 event. The median time to first onset was approximately 0.5 months. Stomatitis led to dose interruption in 6% of patients and dose reduction in 11%. The prescribing information recommends prophylaxis from treatment initiation (steroid-containing mouthwash and oral ice during infusion) and stepwise escalation of supportive care if stomatitis develops. Escalation includes increasing mouthwash frequency, ensuring optimal oral hygiene (soft toothbrush, continued flossing), and adding topical treatments as clinically indicated. For grade 1 stomatitis, treatment may continue at the current dose with intensified supportive care.7
Additional practical considerations (consistent with the prescribing information) include:
- Start a steroid‑containing mouthwash (eg, dexamethasone oral solution 0.1 mg/mL) 4 times daily and as needed, beginning with treatment; hold ice chips/ice water in the mouth throughout infusion.
- Monitor for stomatitis and optimize prophylactic/supportive care. For grade 1 stomatitis, continue Dato-DXd at the current dose while increasing topical measures (eg, steroid-containing mouthwash). For grade 2 stomatitis, withhold Dato-DXd until resolution to grade ≤1 and then restart at the same dose for the first occurrence. For subsequent recurrence at grade 2 or first occurrence at grade 3, restart at a reduced dose (6.0 mg/kg → 4.4 mg/kg → 3.2 mg/kg; a maximum of 2 dose reductions are permitted, and doses may not be re-escalated after reduction). For grade 4 stomatitis, permanently discontinue Dato-DXd.
- Ocular adverse reactions are common with Dato-DXd. Ocular adverse reactions occurred in 36% of patients in the pooled safety population, including grade 3 events in 2.2%. The most common were dry eye (17%), keratitis (14%), and increased lacrimation (7%), with other events including blepharitis, meibomian gland dysfunction, conjunctivitis, and blurred vision. Use preservative-free lubricant eye drops several times daily. Obtain baseline and periodic ophthalmic evaluation. Promptly refer for new/worsening ocular symptoms.
- Monitor for respiratory symptoms suggestive of interstitial lung disease (ILD)/pneumonitis. ILD/pneumonitis is a serious and potentially life-threatening complication of Dato-DXd. In the pooled safety population, ILD/pneumonitis occurred in approximately 7% of patients overall, and in the EGFR-mutated NSCLC population specifically, drug-related ILD was reported in approximately 4% of patients (including 1 grade 3 event). Permanent discontinuation because of ILD occurred in 2.4% of patients across the pooled population, and 79.0% of affected patients required systemic corticosteroids. Median time to onset was approximately 1.4 months. Monitor for respiratory symptoms suggestive of ILD/pneumonitis. If ILD/pneumonitis is suspected, withhold therapy and initiate corticosteroids promptly. Because grade ≥3 ILD/pneumonitis may be life-threatening or fatal, patients with confirmed grade ≥2 ILD/pneumonitis should permanently discontinue Dato-DXd, with urgent evaluation and aggressive supportive management for severe cases.