ESTRO 2019 – Locally advanced NSCLC: safe to reduce PTV-margins and radiation dose to involved lymph nodes

  • Cristina Ferrario — Agenzia Zoe
  • Univadis
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  • In patients with locally advanced non-small cell lung cancer (LA-NSCLC) receiving (chemo)radiotherapy, reduction of planning target volume (PTV)-margins, and inhomogeneous radiotherapy dose prescription to primary tumour and lymph nodes (with lower dose to involved nodes) significantly reduces toxicity, does not cause an increase in regional failure, and improves overall survival (OS).

Why this matters

  • Patients with LA-NSCLC experience oesophageal and pulmonary toxicity, especially when concurrent chemoradiotherapy is applied.

Study design

  • Two cohorts of patients with LA-NSCLC were included in this observational study and treated with hypofractionated radiotherapy (24x2.75 Gy) to the primary tumour.
  • The reference cohort (n=170) received a 24x2.75 Gy (EQD2=70 Gy (α/β=10)) dose scheme to the involved lymph nodes.
  • The reduction cohort (n=138) was treated with a dose of 24x2.42 Gy (EQD2=60 Gy (α/β=10)) to the involved lymph nodes. A reduction of PTV-margins was also applied.
  • The aim of the study was to assess and compare the regional control rate and acute and late toxicity rates after dose and PTV-margins reduction.
  • The influence of patient, tumour, and treatment characteristics on the association between treatment adaptations and outcomes was also assessed.

Key results

  • Patient and tumour characteristics were similar between the two cohorts.
  • The radiation dose to organs at risk (oesophagus, lung, heart, spinal cord) was significantly lower in the reduction cohort.
  • The 2-year regional failure rate was non-significantly lower in the reduction cohort (16.4% vs 9.2%; P=0.415).
  • A significant improvement in OS was observed in the reduction cohort (mean OS: 26 vs 35 months; P=0.006).
  • Grade 2 and 3 acute toxicities were significantly different between the two cohorts and lower in the reduction cohort.
  • Dose reduction also resulted in a non-significantly lower late toxicity (grade ≥3).
  • The association between dose reduction and OS was significantly influenced by the mean lung dose.