For patients with metastatic thymic carcinoma, is there a role for local treatment options such as SBRT for oligoprogressive or oligopersistent disease after systemic therapy?

Of course, there is no data on this question for people with thymic carcinoma. Metastatic thymic carcinoma is generally treated with systemic therapy which is guided to some extent by the histologic subtype of the tumor. Most commonly, we would utilize a regimen such as CAP (cyclophosphamide, doxorubicin, cisplatin/carboplatin) or carboplatin + paclitaxel for up to 6 cycles. If it is a neuroendocrine tumor (small cell or large cell NEC) then carboplatin + etoposide would be most reasonable. Immunotherapy does have activity for recurrent disease, but so far not clear whether the addition of immunotherapy to first line chemo is beneficial.

The few studies that have demonstrated a potential benefit for local treatment (RT, surgery) for oligometastatic disease in solid tumors have primarily treated people with oligopersistent disease after response to first-line systemic therapy. The number of sites has varied in these studies (up to 5), but my belief is that once you get beyond 2-3 sites, you are no longer talking about "oligo" disease. Given the nature of available data in the oligometastatic space, much of the application of local approaches is based on the oncologist's and the patient's inclination for more aggressive therapy in specific individualized situations - the ultimate impact on overall survival will require better long-term prospective trials. If one is inclined to use local treatments for people with oligopersistent disease in people with NSCLC or other solid tumors, then there is probably no reason why such treatment couldn't be applied to people with thymic carcinoma, a rare disease in which we are unlikely to ever get good data in this uncommon clinical situation.

For oligoprogressive disease, when you have achieved good response to systemic therapy and now, with the passage of some time, you see growth of 1 or 2 sites, local treatment to the recurrent sites has become a more accepted approach based on our cumulative experience in patients with mutation-driven  NSCLC who are being treated with targeted therapy.

While the toxicities of local therapy (SBRT, surgery) have improved over the years, it is important to remember that ALL interventions have the potential to cause patient harm. Therefore, it is important to better understand the potential benefits of what we do so that both patients and oncologists can fully gauge the risk:benefit balance and make rational decisions regarding each patient's very individualized care.