Treating extended prostatic small cell neuroendocrine carcinoma (PSCNC) is extremely difficult and no standard treatment has yet been established. We experienced a case of advanced mixed-type PSCNC in which the patient achieved long-term survival and local control following combined therapy. Locally advanced PSCNC causing lower urinary obstruction was detected during androgen-ablation therapy for stage D2 mixed adenocarcinoma PSCNC. The patient was treated with intra-arterial infusion chemotherapy using a reservoir system and external-beam radiotherapy (EBRT) to the whole pelvis and local tumor. After chemoradiotherapy, the patient's lower urinary obstruction was reduced and did not return during the remaining 40 months of the patient's life. The patient survived for 70 months following the start of the androgen-ablation therapy. The present study reports a useful treatment for advanced mixed-type PSCNC, androgen-ablation therapy and chemoradiotherapy. The present results also suggest that the prognostic factors for advanced mixed-type PSCNC are the sensitivity of the conventional adenocarcinoma to androgen-ablation therapy, degree of metastasis and extent of the small cell neuroendocrine carcinoma component.