The magnitude of best tumor shrinkage during second-line targeted therapy affects progression-free survival but not overall survival in patients with metastatic renal cell carcinoma

Objective

The present study aimed to evaluate the influence of the magnitude of best tumor shrinkage during second-line targeted therapy after first-line tyrosine kinase inhibitor failure on metastatic renal cell carcinoma prognosis.

Methods

Fifty-two patients were enrolled. The magnitude of tumor shrinkage was assessed according to the Response Evaluation Criteria in Solid Tumors v. 1.1, and evaluated as a continuous variable and by categorical classification: good responders (greater than or equal to –30%), mild responders (–0.1 to –29.9%), poor responders (0 to +19.9%) and non-responders (greater than or equal to +20% or new lesions). Overall survival and progression-free survival after second-line therapy initiation were evaluated according to the categorical classification. Factors predicting overall survival and progression-free survival were also examined.

Results

The mean magnitude of tumor shrinkage was –1.29%, and there were 9, 21, 11 and 11 good responders, mild responders, poor responders and non-responders, respectively. The overall survival and progression-free survival significantly improved as the magnitude of tumor shrinkage increased according to the categorical classification (overall survival: not reached, 27.8, 18.2 and 4.67 months; progression-free survival: 13.4, 8.19, 5.18 and 1.84 months, respectively; P< 0.0001 for both). For overall survival, the magnitude of tomor shrinkage was not demonstrated as an independent indicator in the multivariate analysis (P= 0.0872 for the categorical classification, P= 0.133 for the continuous variable) whereas for second-line progression-free survival, the magnitude of tumor shrinkage according to both the categorical classification and continuous variable was found to be an independent factor in the multivariate analysis (P< 0.0001 for both).

Conclusions

The magnitude of tumor shrinkage is an independent predictive factor for progression-free survival, and may represent a surrogate marker for overall survival.

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