Neoadjuvant Simultaneous Integrated Boost Radiotherapy Improves Clinical Outcomes for Retroperitoneal Sarcoma: Neoadjuvant Simultaneous Integrated Boost Radiotherapy for Retroperitoneal Sarcoma
Menée à l'aide de données 2000-2021 portant sur 103 patients atteints d'un sarcome rétropéritonéal (durée médiane de suivi : 57 mois), cette étude évalue l'intérêt, du point de vue du contrôle abdominopelvien et de la survie, d'ajouter de manière simultanée un "boost" à la dose standard de radiothérapie néoadjuvante
Résumé en anglais
Background: Neoadjuvant radiotherapy(RT) with standard techniques(ST) offers a modest benefit in retroperitoneal sarcoma(RPS). As the high-risk region(HRR) at risk for a positive surgical margin and recurrence is posterior and away from radiosensitive organs at risk, utilizing a simultaneous integrated boost(SIB) allows targeted dose-escalation to the HRR while sparing these organs. We hypothesized that neoadjuvant SIB RT can improve disease control compared to ST, without increasing toxicity.
Methods: We retrospectively identified patients with resectable non-metastatic RPS from 2000-2021, who received neoadjuvant RT of 180-200cGy/fraction to standard volumes (SV). SIB patients received 205-230cGy/fraction to the appropriate HRR. Clinical endpoints included abdominopelvic control(APC), recurrence-free survival(RFS), overall survival(OS), and acute toxicity.
Results: With a median follow up of 57 months(95%CI 50-64), there were 103 RPS patients who received either ST(n=69) or SIB(n=34) RT. Median standard volume dose was 5000cGy(ST) and 4500cGy(SIB), with a median HRR SIB dose of 5750cGy. Liposarcomas(79% vs 53%, p=0.004) and cT4 tumors(59% vs 19%, p<0.001) were more common in the SIB cohort, without a significant difference in the rate of resection (82% vs 81%, p=0.88) or R1 margin(53.5% vs 50%, p=0.36); there were no R2 resections. SIB was associated with a significant improvement in 5-year APC(96% vs 70%, p=0.046) and RFS(60.2% vs 36.3%, p=0.036), with a non-significant OS benefit(90.1% vs 67.5%, p=0.164). On MVA, SIB remained a predictor for APC(HR 0.07, 95%CI 0.01-0.74; p=0.027) and RFS(HR 0.036, 95%CI 0.13-0.98; p=0.045). SIB showed no significant detriment in toxicity, albeit with a lower rate of overall grade 3 acute toxicity (3% vs. 22%,p=0.023), compared to ST.
Conclusions: In RPS, dose-escalation with neoadjuvant SIB RT may be independently associated with improved APC and RFS, without a detriment in toxicity, when compared to standard techniques. The addition of standard RT having only a modest benefit to surgery alone, our study suggests that future prospective studies evaluating for the benefit of SIB RT should be considered.
