A dose-ranging study of cabozantinib in men with castration-resistant prostate cancer and bone metastases.

BACKGROUND: Cabozantinib is an oral MET/VEGFR2 inhibitor. A recent phase II study of cabozantinib (100 mg daily) showed improved bone scans in subjects with metastatic castration-resistant prostate cancer (mCRPC), but adverse events (AE) caused frequent dose reductions. This study was designed to determine the efficacy and tolerability of cabozantinib at lower starting doses. EXPERIMENTAL DESIGN: An adaptive design was used to determine the lowest active daily dose among 60, 40, and 20 mg. The primary endpoint was week 6 bone scan response, defined as ≥30% decrease in bone scan lesion area. The secondary endpoint was change in circulating tumor cells (CTC). RESULTS: Among 11 evaluable subjects enrolled at 40 mg, there were 9 partial responses (PR), 1 complete response, and 1 stable disease (SD). Of 10 subjects subsequently enrolled at 20 mg, there were 1 PR, 5 SDs, and 4 with progressive disease. Among 13 subjects enrolled on the 40 mg expansion cohort, there were 6 PRs and 7 SDs. No subjects required dose reduction or treatment interruption at 6 or 12 weeks; 3 subjects at dose level 0 discontinued due to AEs by 12 weeks. At 40 mg, median treatment duration was 27 weeks. 58% of subjects with ≥5 CTCs/7.5 mL at baseline converted to <5. CONCLUSIONS: Cabozantinib 40 mg daily was associated with a high rate of bone scan response. Cabozantinib 40 mg daily was associated with better tolerability than previously reported for cabozantinib 100 mg daily. These observations informed the design of phase III studies of cabozantinib in mCRPC.

Immunohistochemistry as an adjunct in the differential diagnosis of radiation-induced atypia versus urothelial carcinoma in situ of the bladder: a study of 45 cases.

Muscle invasive urothelial carcinoma has been treated with cystectomy ± adjuvant therapy. Recently, a bladder-sparing protocol has been offered to selected patients closely followed with surveillance biopsies. In this setting, radiation-induced changes (RAD-Ch) may be very difficult to distinguish from carcinoma in situ, and failing to recognize them may lead to overtreatment. We ascertained the role of immunohistochemistry using cytokeratin (CK) 20, p53, and CD44s in bladder biopsies from 28 patients with a history of bladder radiation and 17 with carcinoma in situ without radiation. Negative or weak multifocal nuclear p53 staining was seen in 24 of 28 RAD-Ch cases, whereas strong and diffuse nuclear p53 staining was found in 8 of 17 carcinoma in situ cases and moderate and focal to multifocal in 3. CK20 showed strong cytoplasmic staining of only umbrella cells in 22 of 28 RAD-Ch cases. In contrast, 11 of 17 carcinomas in situ showed diffuse and strong CK20 positivity and 5 moderate and focal to multifocal positivity. All carcinomas in situ with weak or no p53 showed significant CK20 staining except 1. CD44s displayed diffuse membranous positivity in 7 of 17 RAD-Ch cases and up to mid-third in 8. Only 1 of 17 carcinomas in situ had diffuse membranous CD44s staining. Diffuse and significant CK20 expression was seen in most carcinomas in situ. Strong and diffuse p53 expression was only seen in carcinoma in situ (~50%), whereas diffuse CD44s staining was typically only seen in RAD-Ch. Our data suggest that a CK20(-) p53(-) CD44a panel proves to be very helpful (CK20 more reliable than p53 or CD44s) in the diagnosis of RAD-Ch.