An early Phase II study of intratumoral P‐32 chromic phosphate injection therapy for patients with refractory solid tumors and solitary metastases

BACKGROUND In this early Phase II study, the authors investigated the efficacy of intratumoral injection of P‐32 chromic phosphate in 17 patients with refractory solid tumors or solitary metastases in terms of response rates and overall survival. METHODS Seventeen patients (median age, 60 years) with either cytostatic drug‐resistant tumors or tumors known to be primarily chemotherapy‐resistant were entered into the study. After sonographic determination of the tumor volume, P‐32 chromic phosphate (74–555 MBq) was injected into the central part of the tumor under sonographic guidance. Follow‐up investigations included serial scintigraphy, sonographic examinations, and hematologic studies. RESULTS Injection of P‐32 chromic phosphate into refractory tumors resulted in remarkable regression. The median survival of all patients was 13 months (range, 8–25 months). The response rate was 71% (12 patients). A complete remission was seen in 7 patients (41%), and the rate of partial remissions was 29% (5 patients). However, 5 patients (30%) did not respond to the treatment. In one patient thrombocytopenia was observed, but no other side effects were apparent. Important pathologic and anatomic changes within the tumor tissue were demonstrated in solitary liver metastases of gastrointestinal malignancies excised in second‐look operations. In all cases examined, formation of a cyst within the area of central activity, surrounded by a centrifugal necrotic ring and a marginal fibrotic structure, was found. CONCLUSIONS Lack of persistent systemic or local side effects, as well as noteworthy efficacy, are properties of this optimal regional treatment modality with P‐32 chromic phosphate. This modality deserves consideration for further clinical trials. Cancer 1999;85:980–7. © 1999 American Cancer Society. Intratumoral P‐32 chromic phosphate injection deserves consideration as a new treatment modality for patients with refractory solid cancers or solitary metastases. The response rate found in this Phase II study was 71%.