Peptide receptor radionuclide therapy can be effective in advanced thymus tumors

Objectives Thymus tumors are rare and no established standard treatment exist for advanced stages. Peptide Receptor Radionuclide Therapy (PRRT) with somatostatin analogues 90Y-DOTATOC and 177Lu-DOTATATE is used in patients with neuroendocrine tumors (NETs), like thymus, expressing somatostatin receptors. In GEP NETs previous clinical trials showed complete and partial responses up to 30% of pts, with median survival >48 months. Toxicity is generally mild and involve kidneys and bone marrow. The aim of this study is to evaluate the efficacy of PRRT in 24 patients (14 m, 10 f, aged 42-77 yrs, median 52) affected by metastatic thymus tumors, with positive receptor scintigraphy, in progression after conventional treatments.

Methods Patients received median maximum cumulative activities of 210 mCi (range: 50-355) of 90Y-DOTATOC and 233 mCi (98-813 mCi) of 177Lu-DOTATATE in 2-9 cycles. Patients were divided into 3 groups, according to WHO classification of thymus tumors: group 1 (A --> B2 type), group 2 (B3 type), group 3 (thymus carcinoma).

Results The treatment was well tolerated, without acute and delayed significant side effects. Responses included 4% PR lasting up to 12 months, 54% SD, lasting up to 42 months; 42% of pts did not respond. According to WHO classification we observed: Group 1: 1 PR (13%); 4 SD (50%); 3 PD (37%). Group 2: 6 SD (60%), 4 PD (40%). Group 3: 3 SD (50%); 3 PD (50%).

Conclusions Our results confirm that advance thymus neoplasia show a low response rate and a poor prognosis. However, long-lasting stabilization of disease obtained in more than half of our pts, suggests that combined therapies such as chemotherapy, surgery, radiotherapy and PRRT can be effective in some cases. Further studies on larger cohorts of patients will clarify the exact entity of this benefit