Palliative irradiation for focally symptomatic metastatic renal cell carcinoma: support for dose escalation based on a biological model

Abstract

Purpose: Renal cell carcinoma has traditionally been regarded as a radioresistant cancer, yet controversy continues as to whether escalation of the palliative radiation dose can overcome the inherent resistance of such tumors when they metastasize. Recently, the linear quadratic model has emerged as a paradigm to assess biologically effective dose of radiotherapy. This study was undertaken to determine the ability of radiotherapy to palliate focally symptomatic metastatic renal cell carcinoma and to assess whether the delivery of higher biologically effective dose was more likely to bring about a palliative response.

Materials and methods: Between 1966 and 1995, 107 patients with renal cell metastases at 150 sites were irradiated with palliative intent. Sites irradiated included bone (89), soft tissue (16), brain (20), spinal cord (9) and pulmonary (16). To determine dose effectiveness the biologically effective dose was calculated according to the formula, Gy10 = total dose (1 + fractional dose/alpha-beta), using an alpha-beta of 10.

Results: For the entire group 86% of patients derived a palliative response after treatment with irradiation, while 49% derived a complete palliative response. The median duration of palliation was 6 months (range 1 to 150). With respect to overall (that is, complete and partial) response rates, those presenting with high Karnofsky performance status were most likely to respond (status 70 or greater versus less than 70, 88% versus 78%, p < 0.04). With respect to the rate of complete palliative response, performance status (status 70 or greater versus less than 70, 55% versus 31%, p < 0.03) and the use of higher biologically effective doses of irradiation (Gy10 50 or greater versus less than 50, 59% versus 39%, p = 0.001) were associated with a statistically significant increased rate of response. The independent prognostic value of performance status and higher biologically effective doses of irradiation were maintained in multivariate analysis.

Conclusions: Despite the prevailing concept that renal cell carcinoma is generally resistant to radiotherapy, the overwhelming majority of patients seen at our institution in whom metastatic renal cell carcinoma developed were palliated with radiotherapy. A complete palliative response is more likely when higher biologically effective doses of irradiation are delivered, especially to patients with a relatively high performance status.