154 Background: Metastatic colorectal cancer is common disease that is treated mainly with systemic chemotherapy with or without target therapy combined with local therapies when feasible. Patients with OM-CRC may benefit from local treatments, classically surgery, but more recently SRT is also showing to be effective. We aimed to access the benefit of SRT in patients (pts) with OM-CRC that where not candidates for surgery. Methods: This retrospective study evaluated all the pts with CRC from a single institution that did SRT for OM-CRC. SRT was done with 3D or IMRT/VMAT planning and daily volumetric image. 1-10 fractions were delivered aiming to keep BED > 100Gy10. Dose was decreased as necessary to respect the constraints and minimize toxicity. Progression free survival (PFS) was analyzed from SRT to first progression or death, ST-free survival (STFS) from SRT to the beginning on next ST line or death. Results: We evaluated 32 consecutive pts from Sep/2014 to Jul/2019. Forty-six courses of SRT where performed. Mean age was 56 ± 13y, 60% female and 65% had colon cancer. 52% had metastatic disease after radical treatment. 63% were off ST by the time of the SRT. SRT treatment sites were lung and liver in 28%, bones and lymph nodes 13%, and CNS 11%. 72% of pts had only 1 treated lesion and 70% did 1 SRT course. Most commonly used regimens were 3 x 10-18Gy (35%), 4 x 10-12Gy (15%) and 5 x 7-10Gy (22%). 37% of treatments had BED≥100Gy10 and 78% were done with IMRT/VMAT. With a median follow-up of 16.1m (IQR 8.2-32.7), the median PFS was 5.4m (95% CI 4.1-11.0) and STFS was 12.7m (95% CI 0.8-24.5). Patients with multiple SRT courses had longer interval between disease progression and starting the next ST line (median 2.2 vs 12.4m). Pts that where on ST holidays before SRT had higher STFS (HR = 0.24 95% CI 0.1-0.6, p = 0.001) probably due to selection bias (lower disease volume). The 3y OS was 71%, median was not reached. Conclusions: Local treatment with SRT for OM-CRC showed to be feasible and safe with promising PFS and OS that deserves further investigation. The median STFS superior to a year suggests that SRT can influence OM-CRC treatment positively, possible impacting quality of life and even treatment costs.
825 Background: Metastatic GI cancers are mainly treated with systemic treatment (ST), in selected patients (pts), surgery is considered depending on pts characteristics and institutional preferences. Stereotactic Radiotherapy (SRT) is a growing treatment option in such landscape aiming to improve local disease control and maximize ST results for oligometastatic pts. Methods: This is a single center retrospective study. Data were collected from sequential pts with GI tumors who underwent SRT for OM-GI cancers from May 2014 to July 2019. Information was collected on pts characteristics, primary site, clinical staging at diagnosis, sites undergoing SRT, whether there was progression after the first SRT, time between the first SRT and progression and the last follow-up date. Results: 381 pts underwent SRT in our center, of these, 75 pts had OM-GI tumors and underwent 120 courses of SRT. 50,7% were women, the median age at diagnosis was 60 years and the median follow-up was 36 months. 76% had colorectal cancer (CRC) being 26% from the right, 26% from the left colon and 30% were from the rectum, in 18% of the patients we could not determine sidedness. 35% already had metastatic disease at diagnosis. The lung was the site with largest number of lesions treated with SRT (50), followed by central nervous system (CNS) (42), bones (32), liver (29) and lymph nodes (16). After a median follow up of 15.3 months, 11% of patients were progression-free and only 24% had progressed on treated lesions. The median progression free survival following SRT was 4.5 months (0.6-45.8 range) for distant metastasis and was not achieved for treated sites. Conclusions: This retrospective study adds to the previous body of evidence supporting the use of SRT to improve GI cancer management. Detailed information on pts characteristics, pathology, toxicity and previous treatments will be presented.
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