Background
Retrospective single-institution analysis (Memorial Sloan Kettering Cancer Center) comparing local recurrence rates with conventional EBRT vs. IMRT for primary non-metastatic extremity STS. 319 consecutive patients treated 1996–2010 with limb-sparing surgery + adjuvant RT. Conventional EBRT n=154; IMRT n=165. Median follow-up 58 months. IMRT group had more adverse features (higher grade, positive/close margins, pre-op RT).
Interventions and follow up
Arm A: IMRT (165 patients) — same dose schedules as conventional RT
Arm B: Conventional EBRT (154 patients); retrospective compariso
Primary endpoint: Local recurrence rate
mFollow up: 90 months (conventional), 42 months (IMRT)
Arm B: Conventional EBRT (154 patients); retrospective compariso
Primary endpoint: Local recurrence rate
mFollow up: 90 months (conventional), 42 months (IMRT)
Results
Local Recurrence (multivariable): IMRT HR 0.46, 95% CI 0.24–0.89, P=.02 — significantly reduced
IMRT vs. conventional LR reduction: Despite higher-risk features in IMRT group
Tumor size and margin status: Significant predictors of LR on multivariable analysis
IMRT vs. conventional LR reduction: Despite higher-risk features in IMRT group
Tumor size and margin status: Significant predictors of LR on multivariable analysis
Adverse events
Main adverse events: IMRT associated with reduced late toxicity (less fibrosis, decreased dose to uninvolved normal tissue including bone). Specific grade ≥3 rates not detailed in this retrospective analysis.
Conclusions
IMRT is associated with significantly reduced local recurrence compared to conventional EBRT for primary extremity STS, even after adjusting for the higher proportion of adverse features in the IMRT group (HR 0.46). IMRT should be the preferred RT technique for extremity STS.
Key Limitations
Key Limitations: Retrospective; significantly different follow-up times (90 vs 42 months) favors IMRT in apparent LR rate; selection bias in IMRT group (treated more recently with more advanced techniques); cannot adjust for all confounders; no randomization; single institution.
Clinical Context
IMRT is now the standard RT technique for extremity STS at most major sarcoma centers. Advantages include improved conformality (less dose to surrounding normal tissues — bone, neurovascular structures), reduced late toxicity, and potentially improved local control as shown here. Combined with RTOG contouring consensus (Wang 2011), IMRT has become the modern standard of care.
References