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The following is a summary of “Cumulative rib fracture risk after stereotactic body radiotherapy in patients with localized non-small cell lung cancer,” published in the August 2024 issue of Oncology by Bentsen et al.

Rib fractures are a recognized complication following stereotactic body radiotherapy (SBRT) for localized non-small cell lung cancer (NSCLC). While patient-related factors are crucial for tailoring individual risk estimates, their influence on rib fracture incidence has been less thoroughly investigated than dosimetric factors. This study aimed to assess the risk of rib fractures in patients with localized NSCLC after SBRT by integrating both patient-related and dosimetric parameters, accounting for death as a competing risk.

Researchers conducted a retrospective analysis involving 602 patients with localized NSCLC who received SBRT at Odense University Hospital, Denmark, between 2010 and 2020. The treatment regimen consisted of 45-66 Gray (Gy) administered in three fractions. Rib fractures were detected using CT scans and analyzed with a word embedding model. To estimate rib fracture risk, the investigators employed cause-specific Cox proportional hazards models with variable selection, utilizing cross-validation and bootstrapping techniques.

The results indicated that 19% of the patients experienced rib fractures, with the cumulative incidence of these fractures increasing significantly between 6 and 54 months post-SBRT. Univariable analysis revealed several significant predictors of rib fracture risk, including female gender, low bone density, near maximum dose to the rib, rib volume receiving 30% (V30) and 40% (V40) of the dose, gross tumor volume, and mean lung dose. The final multivariable model, however, identified only the rib volume receiving 20% (V20) and 30% (V30) of the dose, alongside the mean lung dose, as significant predictors of rib fracture risk.

In conclusion, while female gender and low bone density in males are associated with increased rib fracture risk, the final predictive model, which achieved a 19% cumulative rib fracture risk, was predominantly influenced by dosimetric parameters rather than patient-related factors. This suggests that dosimetric considerations are the primary determinants of rib fracture risk in patients undergoing SBRT for localized NSCLC.

Source: sciencedirect.com/science/article/abs/pii/S0167814024007515