PALLIATIVE IRRADIATION FOR FOCALLY SYMPTOMATIC METASTATIC RENAL-CELL CARCINOMA - SUPPORT FOR DOSE-ESCALATION BASED ON A BIOLOGICAL MODEL

Purpose: Renal cell carcinoma has traditionally been regarded as a rad ioresistant 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 ca rcinoma and to assess whether the delivery of higher biologically effe ctive dose was more likely to bring about a palliative response.Materi als and Methods: Between 1966 and 1995, 107 patients with renal cell m etastases at 150 sites were irradiated with palliative intent; Sites i rradiated included bone (89), soft tissue (16), brain (20), spinal cor d (9) and pulmonary (16). To determine dose effectiveness the biologic ally effective dose was calculated according to the formula, Gy(10) = total dose(1 + fractional dose/alpha-beta), using an alpha-beta of 10. Results: For the entire group 86% of patients derived a palliative re sponse after treatment with irradiation, while 49% derived a complete palliative response. The median duration of palliation was 6 months (r ange 1 to 150). With respect to overall (that is, complete and partial ) response rates, those presenting with high Karnofsky performance sta tus were most likely to respond (status 70 or greater versus less than 70, 88% versus 78%, p < 0.043. With respect to the rate of complete p alliative response, performance status (status 70 or greater versus le ss than 70, 55% versus 31%, p < 0.03) and the use of higher biological ly effective doses of irradiation (Gy(10) 50 or greater versus less th an 50, 59% versus 39%, p = 0.001) were associated with a statistically significant increased rate of response. The independent prognostic va lue of performance status and higher biologically effective doses of i rradiation were maintained in multivariate analysis. Conclusions: Desp ite the prevailing concept that renal cell carcinoma is generally resi stant to radiotherapy, the overwhelming majority of patients seen at o ur institution in whom metastatic renal cell carcinoma developed were palliated with radiotherapy. A complete palliative response is more li kely when higher biologically effective doses of irradiation are deliv ered, especially to patients with a relatively high performance status .