How do you approach gastric cancer with oligometastatic disease?

This is an area of ongoing evaluation and controversy. As with any such areas, there is a lot of dogma and no good data (other than single-center retrospective series from East Asia and, occasionally, the West). The FLOT5 study will indeed hopefully answer this question definitively.

FLOT5 is based on what was considered to be promising results from the FLOT3 study (Al-Batran, JAMA Oncol 2017;3:1237), which enrolled 3 separate groups of patients. One such group consisted of patients with "limited metastatic" disease, who were treated with FLOT chemotherapy (5-FU/leucovorin/oxaliplatin/docetaxel) and proceeded to surgery if this was thought to be feasible. Patients who were able to undergo surgery had a more favorable outcome, although this benefit was limited to patients with retroperitoneal lymph nodes as the only site of disease; patients with liver metastases didn't fare so well. We know that patients with limited metastatic nodal involvement can do relatively well so the contribution of surgery to the more favorable outcomes cannot be known. I certainly wouldn't hang my hat on this one very curated observation to advocate for metastectomy.

The other study that is frequently cited -- to argue against metastectomy -- is the Japanese REGATTA study (Fujitana, Lancet Oncol 2016;17:309), in which patients with oligometastatic disease to 1 site (liver, peritoneum or para-aortic lymph nodes) were randomized to either chemotherapy alone or chemotherapy with gastrectomy. This study failed to show a benefit for gastrectomy but cannot be used to disprove the value of metastectomy since the oligometastatic sites were never resected! At most, it suggests that tumor debulking is not a beneficial strategy, which is hardly a shocking conclusion.

In my practice and in our group, metastectomy is reserved for patients who appear to have a unique biology that justifies such surgeries. I personally would consider either surgery, radiation (typically with chemotherapy) or some kind of ablation for patients under the following circumstances: a) true stage IV oligometastatic disease with prolonged progression-free survival on chemotherapy (arbitrarily exceeding at least 1 year); b) oligorecurrent disease following curative therapy, with a long recurrence-free survival from curative therapy and/or a long PFS on palliative chemotherapy started for recurrence or; c) oligoprogressive disease with progression at a single site with otherwise durable control of other sites of disease in a patient with stage IV disease. There is by no means consensus in our group about who exactly to offer locoregional therapy to so these treatments are by far the exception rather than the rule and necessarily have to be individualized. While we should not ignore unusual and favorable biology that could justify locoregional treatments, it is even more imperative that we do not hawk unproven therapies because "it feels right" or because of patient demand.

For the purpose of this response, I've also consciously avoided discussing patients with peritoneal carcinomatosis (either visible on imaging or noted only at laparoscopy in the form of gross disease and/or positive cytology). That is an area of even greater controversy and inflamed opinions, one which FLOT5 will not address.