IGF1 and neoplasm: The outcome of a 42-week study of active acromegalic patients demonstrated that the combined therapy was effective in normalizing the levels of IGF1 and that there was no indication of tumor growth.124 However, an analysis of 62 SRL-resistant acromegalic patients indicated better IGF1 normalization with pegvisomant monotherapy compared to combined pegvisomant/SRL treatment.125 Although pegvisomant is well tolerated and highly effective, some limitations need to be considered.