Optimal doses for the treatment of adrenal metastases with stereotactic radiotherapy (SBRT) are unknown. We aimed to identify dose-volume cut-points associated with decreased local recurrence rates (LRR). A multicenter database of patients with adrenal metastases of any histology treated with SBRT (biologically effective dose, BED10 ≥50 Gy, ≤12 fractions) was analyzed. Details on dose-volume parameters were required (planning target volume: PTV-D98%, PTV-D50%, PTV-D2%; gross tumor volume: GTV-D50%, GTV-mean). Cut-points for LRR were optimized using the R maxstat package. One hundred and ninety-six patients with 218 lesions were included, the largest histopathological subgroup was adenocarcinoma (n = 101). Cut-point optimization resulted in significant cut-points for PTV-D50% (BED10: 73.2 Gy; P =.003), GTV-D50% (BED10: 74.2 Gy; P =.006), GTV-mean (BED10: 73.0 Gy; P =.007), and PTV-D2% (BED10: 78.0 Gy; P =.02) but not for the PTV-D98% (P =.06). Differences in LRR were clinically relevant (LRR ≥ doubled for cut-points that were not achieved). Further dose-escalation was not associated with further improved LRR. PTV-D50%, GTV-D50%, and GTV-mean cut-points were also associated with significantly improved LRR in the adenocarcinoma subgroup. Separate dose optimizations indicated a lower cut-point for the PTV-D50% (BED10: 69.1 Gy) in adenocarcinoma lesions, other values were similar (<2% difference). Associations of cut-points with overall survival (OS) and progression-free survival were not significant but durable freedom from local recurrence was associated with OS in a landmark model (P <.001). To achieve a significant improvement of LRR for adrenal SBRT, a moderate escalation of PTV-D50% BED10 >73.2 Gy (adenocarcinoma: 69.1 Gy) should be considered.
Bibliographical noteFunding Information:
Daniel Buergy reports personal fees from NB Capital ApS, personal fees from Nordic Biotech, personal fees from Siemens AG, personal fees from b.e. Imaging GmbH, outside the submitted work; Juliane Hörner‐Rieber received speaker fees and travel reimbursement from ViewRay Inc, as well as travel reimbursement form IntraOP Medical and Elekta Instrument AB and grants from IntraOP Medical and Varian Medical Systems outside the submitted work; Florian Putz received research grants and speaker fees from Siemens Healthcare AG outside the submitted work; Laila König received speaker fees and travel reimbursement from Accuray and Novocure outside the submitted work; Klaus Henning Kahl is on the advisory board of Bristol Myers Squibb (BMS), MSD, and AstraZeneca; received travel and speakers fees from Varian, Elekta, Zeiss Meditec, Merck, Bristol Myers Squibb (BMS), AstraZeneca and fees from Medical Intelligence outside the submitted work. All the other authors reported no potential conflicts of interest.
© 2022 The Authors. International Journal of Cancer published by John Wiley & Sons Ltd on behalf of UICC.