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Worth Attention soft-tissue-sarcoma

Postoperative SIB shortened sarcoma radiotherapy with no matched outcome differences

A 28-fraction SIB course shortened postoperative soft tissue sarcoma radiotherapy by about one week, with no significant matched outcome or toxicity differences.

RadOncToday · ·1 min read

KEY POINTS

  • This single-centre retrospective study included 275 patients with extremity or trunk soft tissue sarcoma treated after macroscopically complete surgery between 2006 and 2024. 166 received sequential boost RT and 109 received SIB, with propensity score matching used to reduce measured baseline imbalance.
  • Sequential treatment delivered 50 Gy in 25 fractions to the larger volume followed by a 10–16 Gy boost, for a total of 60–66 Gy in 30–33 fractions. SIB delivered 50.4 Gy in 28 fractions with a simultaneous tumor-bed boost to 60.2 Gy in 28 fractions, shortening treatment by approximately one week.
  • After a median follow-up of 57 months, estimated 5-year local recurrence-free survival was 89.5% with sequential boost versus 93.5% with SIB (p=0.300). Unadjusted 5-year DFS was 74.9% versus 84.5%, and DMFS 80.5% versus 88.8%, nominally favoring SIB before adjustment.
  • Those apparent DFS and DMFS advantages weakened after adjustment. SIB was not independently associated with DFS (adjusted HR 0.57, 95% CI 0.30–1.07; p=0.080), DMFS (HR 0.50; p=0.062), LRFS (HR 0.67; p=0.4) or OS (HR 0.26; p=0.084).
  • Propensity score matching produced 96 well-balanced pairs. In this matched cohort, there were no significant differences in LRFS (p=0.672), OS (p=0.214), DFS (p=0.179) or DMFS (p=0.122).
  • Recorded late toxicity was also similar. In the matched cohort, joint dysfunction occurred in 6.3% vs 8.3%, edema in 9.4% vs 13.5%, skin toxicity in 4.2% vs 5.2%, and subcutaneous fibrosis in 4.2% vs 0% for sequential boost versus SIB; none differed significantly. Two grade 4 events occurred in the SIB group, one edema and one skin toxicity.
  • R1 margin status was associated with markedly higher local-recurrence risk (HR 11.0, 95% CI 2.71–44.9), but only seven patients had R1 resections, making this estimate imprecise. The SIB cohort also had shorter follow-up because the technique was introduced more recently.

CLINICAL TAKEAWAY

For postoperative extremity and trunk soft tissue sarcoma, a 28-fraction SIB approach may remove the sequential boost phase and shorten treatment without a detectable penalty in disease control or recorded late toxicity. The data are clinically useful but retrospective and single-centre; propensity matching addresses measured confounding, not unmeasured selection bias, so prospective validation remains important.

SOURCE

Radiation Oncology

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