Abstract
1181
Objectives We noted that bone lesions on CT responded differently than soft tissue lesions to treatment with [177Lu-DOTA0,Tyr3]octreotate (177Lu-octreotate). We therefore compared the response of bone and soft tissue lesions to treatment with 177Lu-octreotate in patients with gastroenteropancreatic neuroendocrine tumors (GEPNETs).
Methods Forty-two patients who 1) had bone metastases that were positive on [111Indium-DTPA0]octreotide scintigraphy (SRS) before treatment, 2) had soft tissue lesions, and 3) had had a minimum of 1 follow-up CT, were studied. Lesions were scored on CT and bone lesions also on SRS before and after treatment. Tumor markers (chromogranin A and 5-Hydroxyindoleacetic acid) before and after treatment were compared.
Results Because bone lesions were not visible on CT before treatment in 11/42 patients (26%), bone and soft tissue lesions were evaluated in 31 patients. Whereas bone lesions increased in size, soft tissue lesions decreased. The difference in percent change of bone and soft tissue lesions was significant (p<0.001). Intensity and/or number of bone lesions on SRS decreased after treatment in 19/23 patients (83%) in whom SRS after treatment was available. The tumor markers also decreased significantly after treatment. In one patient bone lesions became visible on CT after treatment, mimicking progressive disease with ‘new’ bone lesions, whereas there was an overall treatment response.
Conclusions In patients with GEPNETs, the growth of bone lesions or the appearance of new bone lesions on CT after treatment with 177Lu-octreotate should be interpreted very cautiously, as it may be therapy-related rather than indicative of tumor progression