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Mechanistic Deep Dive
SCLC Pathogenesis
- TP53 + RB1 loss universal
- MYC family amplification (~ 20%)
- Neuroendocrine differentiation
- ASCL1 vs NEUROD1 transcription factor subtypes
LEMS Mechanism
- Antibodies against voltage-gated calcium channels (P/Q type)
- Reduced calcium influx â reduced acetylcholine release
- Presynaptic disorder (vs MG postsynaptic)
- Repetitive stimulation â calcium accumulates â improved transmission (âfacilitationâ)
Tarlatamab BiTE Mechanism
- Bispecific T-cell engager
- Engages DLL3 on tumor + CD3 on T-cell
- Activates T-cell killing
- Cytokine release syndrome possible
Recent Trials & Updates
DeLLphi-301 (2024) â Tarlatamab
- Phase 2 in relapsed/refractory SCLC
- 40% response rate
- Median OS 14.3 months
- FDA accelerated approval 2024
- Game-changing for SCLC
Lurbinectedin (PM01183) â 2020 FDA
- Alkylating agent
- Pretreated SCLC
- 35% response rate
IMpower133 (2018) + CASPIAN (2019)
- IO + chemo for ES-SCLC
- Modest survival benefit (12-13 months vs ~ 10 months)
- Standard of care
CONVERT (2017) â Once vs Twice Daily Radiation
- Concurrent chemoradiation in LS-SCLC
- BID 45 Gy (Turrisi trial) and 60-70 Gy daily comparable
- BID earlier completion advantage
ADRIATIC (2024) â Durvalumab Consolidation in LS-SCLC
- Stage III LS-SCLC after chemoradiation
- Durvalumab consolidation
- â Survival
Multiple PARP Inhibitor Trials
- Olaparib + durvalumab + others
- DDR pathway in SCLC
- Mixed results
MYSTIC + POSEIDON
- Combination IO in lung cancers
- Variable outcomes
Tarlatamab + PARP inhibitor + LSDinh combinations
- Earlier phase trials
- Combinatorial strategies
High-Yield Specialist Points
Cisplatin vs Carboplatin
- Cisplatin more nephrotoxic + emetogenic
- Carboplatin renal dose adjusted
- Both effective in SCLC
Etoposide
- Topoisomerase II inhibitor
- Standard SCLC chemotherapy
- Oral + IV
- Side effects: cytopenias, alopecia
Atezolizumab + Durvalumab in SCLC
- PD-L1 inhibitors
- Modest benefit
- Continue maintenance
- Watch irAEs
Tarlatamab Administration
- IV infusion every 2 weeks
- Cytokine release syndrome (CRS) risk (~ 50%)
- Step-up dosing
- Pre-medication, in-patient first doses
- Neurotoxicity (ICANS) possible
- Monitor closely
Spinal Cord Compression
- Emergent: high-dose dexamethasone (10 mg IV)
- Radiation within 24-48 hours
- Surgery for paraparesis < 48 hours
Hyponatremia in SCLC (SIADH)
- Differential: SIADH vs adrenal insufficiency, hypothyroidism, hypovolemia
- Tolvaptan for chronic
- Hypertonic saline for severe acute
- Treatment of cancer addresses
- Demeclocycline alternative
Carcinoid Syndrome
- 5-HT secretion from tumor (often hepatic mets needed for systemic)
- Flushing, diarrhea, bronchospasm, right-sided heart valve disease
- Treatment: octreotide, lanreotide
- Long-acting formulations
Carcinoid Heart Disease
- Right-sided valves (tricuspid, pulmonic)
- 5-HT metabolized in lung; spares left valves
- Mesh-like fibrotic changes
- Echo + surgery if severe
Neuroendocrine Tumor Workup
- Chromogranin A, urinary 5-HIAA
- Somatostatin receptor PET (Ga-68 DOTATATE)
- Imaging
- Biopsy
Future Directions
- Subtype-specific therapy (ASCL1, NEUROD1, POU2F3, YAP1)
- Combinations with tarlatamab
- PARP inhibitor combinations
- New DLL3 + other targets
Pearls
- SCLC: 15%, smokers, aggressive, central, neuroendocrine, TP53 + RB1 universal
- LS-SCLC: chemoradiation + PCI
- ES-SCLC: chemo + atezolizumab or durvalumab (IMpower133, CASPIAN)
- Refractory SCLC: tarlatamab (DLL3 BiTE, DeLLphi-301, FDA 2024) â game-changing
- Lurbinectedin for pretreated SCLC
- Paraneoplastic in SCLC: SIADH, Cushing (ACTH), LEMS, limbic encephalitis
- Squamous â PTHrP (hypercalcemia)
- Adenocarcinoma â HPOA + clubbing
- LEMS vs MG: LEMS improves with effort + anti-VGCC; MG worsens + anti-AChR
- Carcinoid: surgical curative; octreotide for syndrome