eContour

65 year-old man with extensive-stage small cell lung carcinoma due to multiple pleural nodules now s/p carboplatin/etoposide/atezoliumab x 4 cycles with complete mediastinal and pleural response and residual lung mass.

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Technique: IMRT or 3d-conformal RT following systemic chemotherapy.

Dose: 30 Gy in 10 fractions to post-chemotherapy tumor volume as well as hilar and mediastinal nodal stations that were involved pre-chemotherapy (per CREST trial).

Simulation: Supine, alphacradle with arms up. 4D-CT recommended to assess for tumor motion during breathing cycle. The simulation is fused with a pre-chemotherapy PET scan which can be seen using the "select overlay" button. 

 

Case contributed by Fox Chase Cancer Center, Temple University.

Contours per ESTRO ACROP

  • Post-chemo GTV: gross tumor volume including primary tumor and involved nodes, delineated per CT, PET/CT.
  • Post-chemo iGTV: GTV plus margin for tumor motion (contoured directly from maximum intensity projection or from union of GTVs from each phase of the respiratory cycle) - not shown in this case. 
  • Post-chemo ITV: iGTV + 5 mm to account for microscopic disease (crop volume so that ITV does not extend into uninvolved organs such as esophagus, heart, aorta, bone; some practicioners will crop out of lung as shown here).
  • Pre-chemo CTV: includes initially involved hilar and mediastinal nodal stations delineated per CT, PET/CT (crop volume so that CTV does not extend into uninvolved organs such as esophagus, heart, aorta, bone).
  • PTV: ITV + CTV + 5 mm.

  • Per CREST trial, patients with any response after 4-6 cycles of standard chemotherapy (platinum etoposide) should receive thoracic consolidation.
  • Higher doses of thoracic RT (ex 45 Gy in 15 fractions) could be considered for patients with good performance status and excellent response to systemic therapy (RTOG 0937, Jeremic JCO 1999).
  • Immunotherapy during and after chemotherapy can be a first-line approach based on two randomized trials (IMpower133-atezolizumab; CASPIAN-durvalumab).
  • Per the 2020 ASTRO clinical practice guideline, palliative doses of thoracic RT are expected to have limited toxicity and thus can be considered in patients with residual thoracic disease after chemotherapy + immunotherapy.

PCI for extensive stage SCLC:

  • PCI for patients with any response to upfront chemotherapy resulted in reduced symptomatic brain mets and improved OS in a randomized trial (Slotman NEJM 2007).
  • A more recent randomized study showed no difference in overall survival for patients who received PCI compared with MRI surveillance. Thus, MRI surveillance is an acceptable alternative for PCI (Takahashi Lancet Oncol 2017).
  • For patients who do receive PCI, 25 Gy in 10 fractions is standard.