NEW ORLEANS – Early tumor shrinkage may be a reliable indicator of overall survival in patients with metastatic renal cell carcinoma (mRCC) receiving tyrosine kinase inhibitors (TKIs) as first-line therapy, suggest researchers presenting at the 2015 American Urological Association meeting.

Investigators led by Hideaki Miyake, MD, of Kobe University Graduate School of Medicine in Japan, assessed outcomes for 185 Japanese patients with mRCC treated with sunitinib (120) or sorafenib (65) for 3 or more months as first-line therapy. Three patients showed a complete response to therapy, and 40 a partial response. Another 105 patients showed stable disease, while 37 progressed. Median progression-free survival was 7.3 months, and overall survival was 33.6 months.

After 3 months on TKIs, 9 patients experienced tumor shrinkage of 50%–100%; 43 patients, 25%–49%; and 61 patients, 0%–24%. The remaining 72 patients had tumor enlargement or new metastatic lesions. Overall survival rates by level of tumor shrinkage (from greatest to least) were 59, 39, 31, and 16 months, respectively.

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After multivariate analysis, the researchers determined that the following factors were significantly and independently associated with overall survival: Memorial Sloan-Kettering Cancer Center classification, CRP level, liver metastasis, and early tumor shrinkage.

“Considering the potential impact of early tumor shrinkage on the subsequent prognosis of patients with mRCC, it is very important to select first-line agents with an ability to induce prompt tumor remission in order to achieve a favorable prognosis,” Dr. Miyake concluded.