EP-1395: Long term results and technology impact of 48 Gy SABR for inoperable peripheral stage I lung cancer

Abstract

Purpose or Objective Retrospective evaluation of the outcome of patients treated with SABR with curative intent for peripheral stage I lung cancer. Material and Methods In 2007, a SABR protocol was launched for patients with stage I NSCLC. Patients with central lesions, multiple nodules, metastatic lung lesions or synchronous cancers were excluded from this review. A diagnostic PET-CT was obtained for all patients. The prescribed dose was 4 fractions of 12Gy to a total dose of 48Gy for all patients. In 2010, the treatment technology evolved for 3 phases to 10 phases 4D-CT, from type I to type II dose calculations, from multiple conformal beams to VMAT, from movie portal images or megavoltage scans to systematic use of CBCT scan as IGRT method. Local control was defined as the absence of progression. All suspected local relapses were considered as confirmed. Toxicities were graded according to the CTCAE v4.0. Results Between 11/2007 and 06/2016, 300 patients were treated according this SABR protocol. 67 patients treated for metastases, 44 patients treated for multiple nodules and synchronous cancers were excluded, the 189 remaining patients were treated with SABR for a single primary lung lesion. Patients were 46 to 90 years-old, 66% were men, 93% were smokers or ex-smokers. Diagnosis was histologically confirmed in 41% patients (21% adenocarcinoma, 14% SCC, 6% NOS NSCLC), while it was based on radio-metabolic criteria including size increase in 59% patients. AJCC 7 Stage distribution was:T1a: 59%, T1b: 30%, T2: 11%, all patients were N0 and M0. Contraindications to surgery were mostly pulmonary, cardiac, and/or general; only 4% of the patients refused surgery. After 4.1 years of median follow up, the cumulative incidence (analyzed in a competing risks framework) of local, regional and metastatic relapse are respectively 12%, 6% and 16%. After one, two and four years, the OS (estimated with Kaplan-Meier method) was respectively 83 %, 65 % and 37% while the RFS was respectively 75%, 49% and 31%, with a median OS of 37 months. No grade 4 or 5 toxicities were observed. Grade 1 to 3 toxicities were: Fatigue (41%), chest wall pain (10%), dyspnea (7%), radiation pneumonitis (total: 4%, grade 3: 2%), dermatitis (4%), cough (3%), rib fracture (2%), and esophagitis (1%). Metastatic control was significantly better for patients without a previous cancer history (70% versus 59%, cause specific hazard ratio for metastatic relapse 3,04; CI 1,21- 7,66, p = 0.02). We did not detect an impact of tumor stage on survival or loco-regional or distant control. The local control improved for the recent period from 81% to 91 %, raising the hypothesis of favorable impact of new technologies (cause specific hazard ratio for local relapse 0,39, CI 0,15-1,01, p=0,05). Conclusion Local control and other clinical outcomes after SABR for peripheral Stage I lung cancer in this large series of frail patients compares to other reports. Further studies are needed to confirm the positive effect observed with the use of more recent radiation methods.