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ED 01 - Update in Radiation Oncology (ID 1)
- Event: WCLC 2015
- Type: Education Session
- Track: Treatment of Locoregional Disease – NSCLC
- Presentations: 1
ED01.04 - Evolving Role of Radiation for Oligometastases (ID 1773)
14:15 - 15:45 | Author(s): B. Movsas
Evolving Role of Radiation for Oligometastases The key objectives of this presentation are to review the fundamental biology underlying metastatic disease, understand the definition and clinical evidence for oligo- (or limited) metastatic disease, analyze key clinical trials showing the potential role of stereotactic body radiation therapy (SBRT) for oligometastases and address challenges regarding this “high-tech” strategy. In the early 1900s, Halsted suggested that breast cancer spread via the local regional lymphatic vessels in a stepwise manner. Thus, once there are metastases, local therapy had no clear role. Later in the 20[th] century, an opposing theory (the “Fisher” theory) suggested that cancer is a systemic disease that, if it will ever metastasize, will already have done so early in the disease course. Local therapies are therefore less important than systemic therapies. A counterpoint to these approaches was proposed by Hellman and Weichselbaum, postulating that cancer is a spectrum from localized to wide-spread disease at the time of diagnosis, with many intermediate states (Hellman S, Weichselbaum RR. Oligometastases. J Clin Oncol. 1995 Jan;13(1):8-10). “Oligometastases” are essentially early metastases which are limited in number and location and based on a state of limited metastatic capacity. The hypothesis based on this approach is that there may be a subset of patients with oligometastatic disease for whom aggressive local treatment (such as surgery or SBRT) could change their outcome. Clinical evidence for oligometastasis includes the surgical experience for lung or liver metastases showing long-term survivals of approximately 20%. Studies are now emerging suggesting similar results utilizing SBRT. In an individual patient data meta-analysis of outcomes after surgery or SBRT, Ashworth et al. reported a 5-year survival rate of approximately 30% in patients with oligometastatic non-small cell lung cancer (Ashworth AB, et al. An individual patient data metaanalysis of outcomes and prognostic factors after treatment of oligometastatic non-small-cell lung cancer. Clin Lung Cancer. 2014 Sep;15(5):346-55). They developed a risk classification schema showing a better prognosis for metachronous vs. synchronous oligometastases (of which node-negative was favorable to node-positive). Other studies have shown that, among patients treated with SBRT for 1-5 oligometastases, those with ≤3 metastases had better outcomes compared to those with 4-5 metastases. The size of the metastases also appears to be important, as well as the biological equivalent dose (BED) of the SBRT. Studies have begun to explore the role of SBRT for oligometastases involving the lung, liver, adrenal, and other sites. It is likely that host-related factors (for example, immune mediated anti-cancer activity) and tumor related factors (such as genomics and proteomics) also affect the spectrum of disease aggressiveness. Challenges to this new “high-tech” approach will also be addressed, including issues related to patient selection, the level of evidence, and the cost effectiveness of this approach. Other approaches for improving the outcome for patients with metastatic disease will also be discussed, including the role of early palliative interventions. In summary, emerging (albeit non-randomized) data suggests that SBRT appears to be a promising strategy in selected patients with oligometastases. The patients most likely to benefit from SBRT have metachronous (vs. synchronous) metastases, N0 (vs. N+) disease, 1-3 metastases (vs. more), small metastases, and the ability to receive a higher radiation dose (BED >100Gy). Randomized trials are needed to establish whether SBRT improves progression free and/or over survival in this setting.
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