Dose-volume parameters predict for the development of chest wall pain after stereotactic body radiation for lung...

Chest wall (CW) pain has recently been recognized as an important adverse effect of stereotactic body radiation therapy (SBRT) for non-small-cell lung cancer (NSCLC). We developed a dose-volume model to predict the development of this toxicity.

A total of 126 patients with primary, clinically node-negative NSCLC received three to five fractions of SBRT to doses of 40-60 Gy and were prospectively followed. The dose-absolute volume histograms of two different definitions of the CW as an organ at risk (CW3cm and CW2cm) were examined for all 126 patients.

With a median follow-up of 16 months, the 2-year estimated actuarial incidence of Grade ≥ 2 CW pain was 39%. The median time to onset of Grade ≥ 2 CW pain (National Cancer Institute Common Terminology Criteria for Adverse Events, Version 3.0) was 9 months. There was no predictive advantage for biologically corrected dose over physical dose. Neither fraction number (p = 0.07) nor prescription dose (p = 0.07) were significantly correlated with the development of Grade ≥ 2 CW pain. Cox Proportional Hazards analysis identified significant correlation with a broad range of dose-volume combinations, with the CW volume receiving 30 Gy (V30) as one of the strongest predictors (p < 0.001). CW2cm consistently enabled better prediction of CW toxicity. When a physical dose of 30 Gy was received by more than 70 cm(3) of CW2cm, there was a significant correlation with Grade ≥ 2 CW pain (p = 0.004).

CW toxicity after SBRT is common and long-term follow-up is needed to identify affected patients. A volume of CW ≥ 70 cm(3) receiving 30 Gy is significantly correlated with Grade ≥ 2 CW pain. We are currently applying this constraint at our institution for patients receiving thoracic SBRT. An actuarial atlas of our data is provided as an electronic supplement to facilitate data-sharing and meta-analysis relating to CW pain.