eContour

76-year-old man with Stage IA (ypT1, pN0, cM0) malignant left parietal pleura epithelioid mesothelioma. He underwent neoadjuvant chemotherapy with carboplatin, pemetrexed, and bevacizumab followed by a left extended pleurectomy and decortication. There was no gross residual disease following surgery.

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Rx:

  • 45-60 Gy in 1.8-2 Gy fractions depending on margins and gross residual disease.
  • Start RT 4-8 weeks following surgery or adjuvant chemotherapy.

Chemotherapy: 

  • Given as either induction prior to surgery or adjuvant following surgery.
  • It is not given concurrent with radiation.
  • Cisplatin/pemetrexed and cisplatin/pemetrexed/bevacizumab are two common first line regimens.

Sim/Planning:

  • Simulation is to be performed supine, in a Vac-Lok, and a wing board (arms abducted bilaterally with hands above the head).
  • CT slice thickness is to be 3 mm.
  • 4D CT scan or motion management technique (breath hold, real-time position management, surface imaging, or abdominal compression) should be used.
  • PET CT should be fused if available.
  • IMRT with 6-10 MV beams is appropriate.
  • CBCT daily for image guided RT.

 

Case contributed by University of Cincinnati Medical Center

 

Per NRG LU-006

GTV

  • Gross tumor based on CT and PET

CTV (combined CTV_Inner and CTV_Outer)

  • CTV_Inner: lung/chest wall interface on slices without GTV; 3 mm internal margin surrounding the GTV on slices with GTV.
  • CTV_Outer: lung/chest wall interface on slices without GTV; 3 mm external margin surrounding the GTV on slices with GTV.
    • Below the level of the diaphragm, CTV_Outer needs to be mannually expanded to cover the pleura towards the sternum, the diaphragm and diaphragmatic crura to midline anteriorly, and the paravertebral space posteriorly.
  • The CTV_Inner and CTV_Outer are not a wall like structure, but function as a guide for the creation of the final PTV that encompasses all the pleura and entire thickness of the chest wall.
  • Where there is no GTV and lung is still present, the CTV_Inner and CTV_Outer should be the same structure.

ITV

  • ITV_Inner: internal expansion of the CTV_Inner to account for respiratory and cardiac motion seen on 4DCT scan.
  • ITV_Outer: external expansion of the CTV_Outer to account for respiratory and cardiac motion seen on 4DCT scan.

PTV

  • PTV_Inner: 6mm internal expansion of the ITV_Inner, this is to expand into lung parenchyma
  • PTV_Outer: 10mm external expansion of the ITV_Outer; where necessary, the PTV_Outer will be further adjusted to cover the entire thickness of the chest wall, including the ribs and intercostal muscles; it will be expanded to the lateral edge of the sternum or midline anteriorly, the costovertebral joint and the lateral edge of the vertebral body, the costodiaphragmatic and costomediastinal recess and the crus of the diaphragm. Volumes extend inferiorly to the L2 vertebral body.
  • Below the level of the diaphragm use only PTV_Outer.
  • The PTV for planning purposes is the PTV_Outer minus the PTV_Inner, which ends up being a wall like structure.

OARS:

  • Lungs-GTV: V20 Gy ≤ 37%
  • Ipsilateral lung: V40 Gy ≤ 67%
  • Contralateral lung: V5 Gy ≤ 50%, Mean ≤ 8 Gy, V20 Gy ≤ 5%
  • Heart:
    • Mean dose ≤ 30 Gy
    • Right-sided disease: V40 Gy ≤ 25%
    • Left-sided disease: V40 Gy ≤ 35%
  • Esophagus: Mean dose ≤ 34Gy
  • Bowel: D5cc ≤ 45 Gy
  • Stomach-PTV: Mean dose ≤ 30Gy
  • Kidneys: V18 Gy ≤ 33%