Author of

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  P49 - Small Cell Lung Cancer/NET - Radiotherapy (ID 237)

  • Event: WCLC 2020
  • Type: Posters
  • Track: Small Cell Lung Cancer/NET
  • Presentations: 1
  • Moderators:
  • Coordinates: 1/28/2021, 00:00 - 00:00, ePoster Hall

  • 36202

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    P49.01 - Treatment Planning QA of Hippocampal Avoidance Prophylactic Cranial Irradiation in the Multicenter Randomized Phase III Trial (NCT01780675) (ID 1011)

    00:00 - 00:00  |  Presenting Author(s): Oscar Lawrence Candiff
    • Abstract
    • Slides

    Introduction
    

    NCT01780675, a multicenter randomized phase III trial of prophylactic cranial irradiation (PCI) versus PCI with hippocampal sparing (HA-PCI) in Small Cell Lung Cancer (SCLC) investigated neurocognitive decline and safety. As part of quality assurance, we analyzed if the dose distribution met the trial constraints for all patients receiving HA-PCI.

    Methods
    

    Patients with limited or extensive stage SCLC who received PCI were randomized to standard PCI or HA-PCI, using IMRT or VMAT. For the HA-PCI group, dose distribution constraints were as follows: mean dose to the hippocampi ≤ 8.5 Gy (BED ≤6.1 Gy for α/β=2Gy), D1% hippocampi ≤ 10 Gy, V95% planning target volume (PTV) ≥ 95%, V115% PTV ≤ 1%, D98% PTV ≥ 18.75 Gy (75%), D1% PTV ≤ 27.5 Gy (110%) and Dmax PTV ≤ 28.75 Gy (115%). The dose distribution for each patient receiving HA-PCI was retrieved and analyzed to evaluate if the dose constraints were met.

    Results
    

    From April 2013 until March 2018 a total of 168 patients were randomized in the NCT01780675 study in 10 centers in the Netherlands and Belgium. The primary endpoint revealed no significant difference on neurocognition between the two treatment arms at 4 months*. 82 patients receiving HA-PCI without evidence of brain metastases were analyzed. All patients were treated with 25 Gy in 10 fractions. Violations of dose constraints are listed in the Table. The average mean bilateral hippocampal dose was 7.9 Gy, range 5.4 – 11.4 (constraint ≤ 8.5 Gy). In six patients (7.3%) there was a protocol violation of the mean dose in one or both hippocampi. In four of these six patients (4.9%) the mean dose to both hippocampi exceeded the constraint, in 1 patient (1.2%) only the left and in 1 patient (1.2%) only the right hippocampal mean dose was violated (average mean dose left and right 9.2 Gy). All patients met the trial constraint of V115% PTV ≤ 1%, however the Dmax PTV of ≤ 28.75 Gy was violated in 22.0% of the patients.

    *Belderbos et al R&O 2019 S259

    

    Conclusion
    

    This QA on trial constraints for patients receiving HA-PCI in the multicenter randomized phase III trial concludes: treatment plans complied with the trial constraints in the vast majority of cases. For 93% of the patients the trial constraint on the mean dose to the hippocampi was achieved (≤ 8.5 Gy). In all treatment plans the volume of the PTV receiving 115% of the prescribed dose did not exceed 1%.

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