[177Lu-DOTA 0-Tyr 3]-octreotate treatment in patients with disseminated gastroenteropancreatic neuroendocrine tumors: the value of measuring absorbed dose to the kidney.

Peptide receptor radiation therapy (PRRT) using [(177)Lu-DOTA(0)-Tyr(3)]-octreotate is a new, promising option for treatment of disseminated gastroenteropancreatic neuroendocrine tumors (GEPNETs). During 2006-2008, 26 patients with disseminated GEPNETs were treated with (177)Lu-octreotate. Radiologic response (RECIST), biochemical response [plasma chromogranin-A (P-CgA)], hematologic toxicity [Common Toxicity Criteria (CTC)], absorbed dose to the kidneys (conjugate view method), and glomerular filtration rate (GFR) were analyzed. (177)Lu-octreotate (8 GBq) was given one to five times (median = 3) with a 6-week interval between each. Sixteen of the 26 patients were evaluated radiologically; 6 (38%) had partial response (PR), 8 (50%) had stable disease (SD), and 2 (13%) had progressive disease (PD). Seventeen of the 26 patients were evaluated biochemically; 6 (35%) showed a >or=30% decrease, 8 (47%) showed a >or=20% increase, and 3 (18%) showed neither a >or=30% decrease nor a >or=20% increase. The mean absorbed dose to the kidneys was 24 Gy. With a dose limit of 27 Gy to the kidneys, 10 patients did not receive the planned four treatments, while four patients had the potential to receive additional treatment. A significant reduction (p = 0.0013) of GFR was observed at follow-up. Three patients experienced CTC grade 3 hematologic toxicity. By using the absorbed dose to the kidneys as a limiting factor, treatment with (177)Lu-octreotate can be individualized, e.g., overtreatment can be avoided and patients with the potential to receive additional treatment can be identified. Further studies are needed to define tolerance doses to the kidneys so that treatment can be optimized.