A 58-year-old man with stage IV NSCLC and a ROS1 fusion who develops dyspnea on crizotinib
A 58-year-old man with a 30-pack-year smoking history presents with stage IV lung adenocarcinoma, with a malignant pleural effusion and a 2.5-cm right lower lobe mass. Molecular testing shows a ROS1 fusion and no EGFR, ALK, BRAF, KRAS, or MET alterations; PD-L1 tumor proportion score is 0%. He is started on crizotinib. After 6 weeks he reports worsening dyspnea, and imaging shows stable tumor size but new bilateral ground-glass opacities. His oxygen saturation is 88% on room air, and he is admitted. He is afebrile with a normal white count. He asks whether the drug is working and what should be done.
1. What is the most likely diagnosis, and how would you manage it?
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The most likely diagnosis is crizotinib-induced pneumonitis (drug-induced interstitial lung disease).
Reasoning:
- Crizotinib can cause severe, sometimes fatal, interstitial lung disease, typically within the first few months of therapy.
- The presentation-new bilateral ground-glass opacities, hypoxemia, and dyspnea without fever or leukocytosis-favors drug-induced pneumonitis over infection or progression (tumor size is stable).
- Management: hold crizotinib immediately, give supplemental oxygen, and start corticosteroids (e.g., prednisone 1 mg/kg/day or equivalent) for moderate-to-severe cases. Obtain cultures and consider empiric antibiotics until infection is excluded. Avoid rechallenge with crizotinib; if the patient recovers and needs ROS1-directed therapy, switch to an alternative ROS1 inhibitor such as entrectinib or repotrectinib, with close monitoring.
- The patient should be told the drug may still be effective against the tumor, but the pneumonitis is a separate, potentially life-threatening toxicity.
2. If he recovers and needs to resume ROS1-directed therapy, what would you choose and why?
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Options include entrectinib or repotrectinib, both potent ROS1 inhibitors with CNS activity.
Reasoning:
- Crizotinib rechallenge is generally avoided after severe pneumonitis.
- Entrectinib is approved for ROS1-positive NSCLC and has good intracranial activity; common toxicities include fatigue, dysgeusia, edema, diarrhea, and weight gain, and it can cause QT prolongation and cognitive effects.
- Repotrectinib is a next-generation ROS1/TRK inhibitor with activity against resistance mutations and CNS disease; it can cause dizziness, dysgeusia, and paresthesias.
- Choice depends on CNS disease burden, tolerability, and formulary availability. Baseline and periodic ECG, liver function, and CNS imaging are appropriate.
- If he had developed progressive disease rather than toxicity, repeat molecular testing (tissue or liquid biopsy) would guide selection of a next-generation inhibitor.
3. What is the role of immunotherapy in this patient, and why?
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Immunotherapy is not first-line here.
Reasoning:
- He has a ROS1 fusion, which is an actionable driver alteration. Guidelines recommend a targeted ROS1 inhibitor as first-line therapy for ROS1-positive advanced NSCLC, regardless of PD-L1 status.
- PD-L1 is 0%, further reducing the likelihood of benefit from single-agent immunotherapy.
- Immunotherapy can be considered later after progression on targeted therapy and platinum chemotherapy, but responses in ROS1-positive tumors are generally lower than in EGFR/ALK-negative disease, and immune-related toxicity must be weighed.
- The key teaching point is that driver mutation status trumps PD-L1 for first-line decision-making in oncogene-addicted NSCLC.