Impact of Adjuvant and Salvage Radiation Therapy in Conventional Type 2 Chondrosarcomas

Introduction: The most common adjuvant treatment methods for chondrosarcomas include high-dose radiotherapy either with proton beam radiation or stereotactic radiosurgery (SRS), but the application in conventional type 2 (cCSA 2) is a matter of debate. Compared to EBRT or SRS, proton-based radiotherapy offers a better capability to cover the complex geometrical configuration of these tumors while sparing surrounding critical neurovascular structures. However, the benefit of radiation therapy in complete surgical resection and the best moment of application has to be determined.

Methods: The authors conducted an analysis of the retrospectively collected multicenter database from the Skull Base Chondrosarcoma Consortium. Patient demographics, radiologic features, and treatment outcomes of patients with cCSA 2 were reviewed. Clinical and radiological follow-up information was assessed to determine the stability or progression of the disease after different treatment modalities. Radiation modalities and surgical outcomes were extensively analyzed to determine their impact on progression-free survival.

Results: A total of 71 patients with cCSA 2 were identified ([Table 1]). The mean patient age was 47.9 ± 17.2 years, and 58% were women. The mean follow-up time was 79.8 (range: 1.7–306.4 months). Thirty-seven were treated with surgery + close follow-up (52.1%) and thirty-four (47.9%) with surgery plus radiation therapy (RT). Gross total resection was achieved in 24 patients (33.8%) and adjuvant RT was most frequently used after subtotal resections (n = 27, 79.4%). The prevailing RT technique used was proton-based radiotherapy (73.5%; [Table 2]). Comparing the groups surgery + close follow-up and surgery + RT, the 2-year, 5-year, and 10-year survival rates were 79, 53, and 23% and 94, 76, and 19%, respectively (HR: 1.29; 95% CI: 0.73–2.31; p = 0.065).

In terms of progression-free survival (PFS; [Fig. 1A] and [Table 3]), adjuvant RT significantly decreased the likelihood of disease progression (HR: 5.13; 95% CI: 2.04–12.9; p = 0.0001). Considering the different extent of resection, adjuvant RT has shown a significant PFS improvement ([Fig. 1B]) after incomplete resection (HR: 4.66; 95% CI: 1.52–14.3; p = 0.0004) but appears to have no benefit after complete resection (HR: 0.15; 95% CI: 0.02–1.11; p = 0.064). Moreover, RT has shown a prognostic benefit even when used as salvage therapy (HR: 5.12; 95% CI: 1.81–14.5; p = 0.002) and there were no differences in the radiation failure-free survival (RFFS) when radiation was applied as adjuvant or salvage sequences (p =.16). Proton-based RT (PBRT) was significantly better than photon-based showing a 5.7-fold increase in the disease control over time (p = 0.01; [Fig. 1C]) with a higher concentrated dose at the tumor volume (68.6 Gy in PBRT vs. 61.7 Gy in EBRT, p = 0.006; [Fig. 1D]). On a COX regression multivariate analysis, only EOR and Treatment modality were independent predictors of recurrence (p = 0.003).

Conclusions: Surgery plus close follow-up after complete resection in cCSAs type 2 appears to be an acceptable decision. The PFS impact of RT is more important after an incomplete resection, and this prognostic impact remains even when used as a salvage therapy. The capacity of PBRT to concentrate higher radiation doses in the tumor site appears to be an important factor in the local control.

Table 1

Table 2

Fig. 1 Kaplan–Meier curves for PFS.

Table 3

 

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Artikel online veröffentlicht:
05. Februar 2024