Stereotactic Ablative Radiotherapy for Pulmonary Metastases : Histology, Dose and Indication Matter
Menée sur 120 patients présentant une ou plusieurs métastases pulmonaires (durée médiane de suivi : 22 mois), cette étude évalue, du point de vue notamment de l'échec local et du recours à une chimiothérapie systémique, l'efficacité d'une radiothérapie stéréotaxique ablative en fonction de l'origine et du type de métastases ainsi que de la dose de rayonnements reçus
Purpose : To assess the association between colorectal cancer (CRC) histology, dose and local failure (LF) after stereotactic ablative radiotherapy (SABR) for pulmonary metastases, and to describe subsequent cancer progression, change of systemic therapy (CST), survival and their association with treatment indications. Materials and Methods : From a prospective SABR cohort, 180 pulmonary metastases in 120 patients were identified. Treatment indications were: single metastasis, oligometastases, oligoprogression, and dominant areas of progression. Doses of 48-52Gy/4-5 fractions were delivered. Since 2010 the dose for peripheral CRC metastases was increased to 60Gy/4 fractions. Cumulative incidence function (CIF) was used to report LF, progression probability and CST. Kaplan-Meier method estimated overall survival (OS). Univariate and multivariable analyses to assess variable associations were conducted. Results : Median follow-up was 22 months (IQR:14-33). At 24 months, the CIF of LF was 23.6% (95%CI:15.1-33.3) and 8.3% (95%CI:2.6-18.6) respectively for CRC and non-CRC metastases (p<0.001). This association remained significant after adjusting for confounders (subdistribution hazard ratio (SHR):13.6, 95%CI:4.2-44.1, p<0.001). Among CRC metastases, 56 and 45 received <60Gy and 60Gy respectively. Delivering 60 Gy was independently associated with a lower hazard of LF (SHR:0.271, 95%CI:0.078-0.940, p=0.040). At 12 months the CIF of progression was 41.67% (95%CI:21.69-60.56), 42.51% (95%CI:29.09-55.29%), 62.96% (95%CI:41.25-78.53%) and 78.57% (95%CI:42.20-93.48%) respectively for patients treated for single metastasis, oligometastases, oligoprogression and dominant area of progression (p<0.001). A CST was observed respectively in 4 (17%), 17 (31%), 12 (44%) and 10 (71%) patients with a median time of 13.1, 11.1, 8.4 and 8.4 months. Conclusion : CRC lung metastases are associated with a higher hazard of LF and require higher SABR doses. Outcomes for patients with oligometastases and oligoprogression treated with SABR seem favorable. Prospective clinical trials are needed to confirm these benefits.