Role of Surgery in Patients with Stage IE Primary Thyroid MALT Lymphoma Staged by a Modified Classification System: The Tokyo Classification

SIMPLE SUMMARY: The therapeutic strategy for and the staging system of primary thyroid mucosa-associated lymphoid tissue (MALT) lymphoma are not established. We conducted a retrospective analysis to (i) establish the appropriate staging system and (ii) assess the role of curative thyroidectomy vs. involved-site radiation therapy (ISRT) after open biopsy in stage IE MALT lymphoma. The modified staging system allows us to distinguish between stages IE and IIE primary thyroid MALT lymphoma. Information about the side effects under ISRT may have limited informative value, but approximately one in three to four patients had radiation-induced permanent complications (mainly dry mouth). Curative thyroidectomy provides good prognoses, equivalent to that of ISRT after open biopsy; it avoids permanent dry mouth, shortens painful periods during treatment, and simplifies ultrasound follow-ups. In the NCCN guidelines, ISRT is the preferred initial therapy for limited-stage non-gastric MALT lymphoma. However, curative thyroidectomy alone can serve as the initial treatment equivalent to ISRT post-open-biopsy. ABSTRACT: Purposes: To establish the appropriate staging system and assess the role of curative thyroidectomy alone (Surgery) vs. involved-site radiation therapy after open biopsy (OB-ISRT) in stage IE mucosa-associated lymphoid tissue (MALT) lymphoma. Methods: We examined the Tokyo Classification as a modified classification. This retrospective cohort study included 256 patients with thyroid MALT lymphoma; 137 underwent standard therapy (i.e., OB-ISRT) and were enrolled for the Tokyo classification. Sixty stage IE patients with the same diagnosis were examined to compare Surgery with OB-ISRT. Results: Overall survival (p = 0.0092) and relapse-free survival (0.00113) were significantly better in stage IE vs. stage IIE under the Tokyo classification. No OB-ISRT and Surgery patients died, but three OB-ISRT patients relapsed. The incidence of permanent complications was 28% in OB-ISRT (mainly dry mouth) and 0% in Surgery (p = 0.027). The number of painkiller prescription days was significantly greater in OB-ISRT (p < 0.001). During follow-up, the rate of the new appearance/change of the low-density area in the thyroid gland was significantly higher in OB-ISRT (p = 0.031). Conclusions: The Tokyo classification allows an appropriate discrimination between stages IE and IIE MALT lymphoma. Surgery can provide a good prognosis in stage IE cases; it also avoids complications, shortens painful periods during treatment, and simplifies ultrasound follow-up.