Abstract
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.
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