How would you approach a patient with high-grade gastric lymphoma who achieved a CR following chemotherapy?

About half of all lymphomas arising in the stomach are high-grade non-Hodgkin lymphomas, primarily DLBCL. Initial treatment would consist of chemoimmunotherapy (R-CHOP). The number of cycles of systemic therapy, and whether consolidation RT is appropriate, would depend upon stage, extent of disease in the stomach, and presence of other risk factors (e.g. age, LDH, performance status).

In general, NCCN guidelines for DLBCL would be appropriate. For rare patients with stage I/II, non-bulky disease, without risk factors, treatment could consist of either R-CHOP X 4 or R-CHOP X 3 + RT (30 Gy). In my experience, most patients with gastric DLBCL present with a more advanced disease warranting a more aggressive approach (6 cycles of chemotherapy, often with consolidation RT).

Partial organ irradiation (as opposed to MALT) is appropriate if the disease is well circumscribed and involves only a portion of the stomach (e.g., only the pylorus). I give either 1.5 or 1.8 Gy fractions depending on whether I'm treating the whole stomach or just partial organ. With stage I-II disease, I would give 30 Gy. For stage III-IV disease, with PET-CT CR after 6 cycles, our institutional policy for many years has been to give 20 Gy.