Postoperative radiation therapy for osseous metastasis: Outcomes and predictors of local failure.

PURPOSE

To evaluate patterns and predictors of local failure in patients undergoing postoperative radiation therapy (RT) for osseous metastases.

METHODS AND MATERIALS

Patients undergoing postoperative RT for bone metastases between June 2008 and January 2012 were retrospectively reviewed. Patterns of local failure were assessed, and Fine and Gray's univariable and multivariable analyses (MVA) were used to evaluate factors associated with local progression, including dose intensity of RT (biological equivalent dose, BED, Gy10) and percent coverage of the surgical hardware by the RT fields. Additional predictors were similarly assessed, including patient (eg, age, performance status), disease (eg, tumor type, metastasis site), and treatment (eg, interval from surgery to RT) characteristics.

RESULTS

A total of 82 cases were followed for a median of 4.3 months (11.5 months among living patients) after treatment completion. Median BED was 39 Gy10 (range, 14-60), and RT fields covered an average of 71% (standard deviation, 26%) of the hardware. Fourteen cases (17%) experienced local progression. Although most (71%) failures occurred within the RT fields, 29% occurred marginally or out of field, but adjacent to surgical hardware. Increasing coverage of the surgical hardware by RT fields was associated with a reduced risk of local failure in MVA (hazard ratio [HR], 0.10; 95% confidence interval [CI], 0.012-0.82; P = .03), whereas a greater risk of failure was seen with increasing time between surgery and RT (HR, 1.03; 95% CI, 1.01-1.06; P = .01). Extremity rather than spinal site trended toward a greater risk of failure but did not reach significance (HR, 3.79; 95% CI, 0.96-14.89; P = .057). BED ≥39 Gy10 did not predict local failure (P = .51) in MVA.

CONCLUSIONS

Current strategies achieve good outcomes after postoperative RT for osseous metastases. Greater coverage of the surgical hardware with RT fields and avoiding delays between surgery and postoperative RT should be considered to reduce recurrence risk for patients with bone metastases requiring surgical stabilization.