Late Toxicity And Long-Term Local Control In Patients With Ultra-Central Lung Tumors Treated By Imrt Based Stereotactic Ablative Body Radiation Therapy (Sabr)

To report the late toxicity and long term local control of IMRT- based SABR in patients (pts) with ultra-central lung tumors, treated in a single institution. This is a retrospective review of 50 pts with ultra-central tumors treated by SABR, from May 2008 to April 2016. All pts had minimum 6 months (mts) follow-up (FU) post-SABR. Ultra-central location was defined as tumor abutting or involving trachea, main or lobar bronchi (airways). Respiratory management was used in all pts. Radiation schedule was at physician preference. Treatment was delivered using a medical linear accelerator. Late toxicity (>6months post-SABR) and local control (LC-absence of local progression) were analysed. Descriptive analysis, Kaplan Meier, log-rank test and Cox regression were used to assess the outcomes. Late toxicity was graded according to CTCAE v.4. Data was censored at the last known follow-up or death. There were 26 males (52%) and 24 females (48%), with a median age of 72.5 years old (34 - 85) and median KPS = 80 (60-100). 33 pts (66%) had inoperable primary NSCLC and 17 (34%) lung metastases. The median gross tumor volume (GTV) and median planning target volume (PTV) were 16.73cc (1.7 -136.85), and 56.4 cc (7.7 – 307) respectively. Most commonly used dose fractionation was 60 Gy/ 8fx in 43 pts (86%) . The median D98%PTV - was 58.94Gy (21.5-62.96), and the median D2% PTV= 64 Gy (43.11 – 79.5). In 10 pts dose painting was used to spare the airways, leading to D98% PTV < 90% in 9 pts and D98% GTV < 90% in 7 pts. One pt. was lost of FU. With a median FU of 25.5mts (7.43-92.68), significant late toxicity (> G3) occurred in 8 pts (16%): G3 cough– 1pt (2%), G3 aspiration- 1pt (2%), G3 fatigue – 1pt (2%), G3 dyspnea – 1pt (2%). G5 hemoptysis was observed in 4pts (8%), after a median of 12.7 mts (11.4- 54.6) from SABR: in 2pts (4 %) was undeniably SABR-induced (pts with complete metabolic response) and in 2 pts (4%) occurred concomitantly with local progression (LP). No correlation between airways DVH parameters and risk of hemoptysis could be identified (p=0.6). At the last known FU, LC was observed in 43pts (86%); most of the LPs (5 of 7) were observed more than 24 months from SABR. None of the dosimetric or clinical parameters were correlated with LC. In patients with ultra-central lung tumors, SABR achieves high local control, similar to that reported for peripheral tumors. While fatal hemoptysis was observed in 8% of the patients, in 4% of them it was definitely related to SABR only.Abstract TU_23_3548; Table 1Dose fractionation, respiratory management and airways DVH parameters.Number patients%Dose fractionation60Gy/8fx438648GY/4fx3650Gy/10fx3640Gy/5fx12Respiratory managementGated816Free breathing non-gated2856Breath-hold1428Airways DVH parameters40Gy IDL circumferential2242Dose to 1cc (median±StDev)51.8Gy±13.9(5.17-64.3)Dose to 5cc (median±StDev)45.2Gy±14.5(4.4-63.5)Abbrivations: fx = fraction; DVH = dose volume histogram; IDL = isodose line; StDev = standard deviation. Open table in a new tab