Dose-effect analysis of radiation induced rib fractures after thoracic SBRT

Radiother Oncol. 2017 May;123(2):176-181. doi: 10.1016/j.radonc.2017.01.004. Epub 2017 Jan 19.

Abstract

Background and purpose: To determine a dose-effect relation for radiation induced rib fractures after stereotactic body radiation therapy (SBRT) in early stage non-small cell lung cancer (NSCLC). Automatic rib delineation has enabled the analysis of a large patient group.

Material and methods: Four-hundred and sixty-six patients with stage I/II NSCLC received SBRT with a median of 54Gy in 3 fractions. The optimal EQD2-corrected dose parameter to predict (a)symptomatic fractures was found using Cox regression. Three normal tissue complication probability (NTCP) models based on this optimal parameter were constructed: (1) at a median follow up (FU) of 26months, (2) for all data, with time to toxicity taken into account and (3) at a FU of 26months, excluding low dose ribs.

Results: The median time to fracture was 22 (range 5-51) months. Maximum rib dose best predicted fractures. The TD50 (dose with 50% complication) of the second NTCP model was 375Gy. The TD50 was significantly higher for the other models indicating an under-estimation of the dose effect at the median follow-up time and/or when excluding low dose ribs.

Conclusions: The risk of symptomatic rib fractures after SBRT was significantly correlated to dose, and was <5% at 26months when Dmax<225Gy.

Keywords: Dose–effect; Lung cancer; NTCP; Rib fracture; SBRT.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Carcinoma, Non-Small-Cell Lung / radiotherapy*
  • Dose-Response Relationship, Radiation
  • Female
  • Humans
  • Lung Neoplasms / radiotherapy*
  • Male
  • Middle Aged
  • Radiation Injuries / etiology*
  • Radiosurgery / adverse effects*
  • Rib Fractures / etiology*