Responses of Renal Cell Carcinomas to 29 Different Systemic Anti-Cancer Therapies

Introduction: The prevailing view is that renal cell carcinomas (RCCs) are resistant to chemotherapy. However, it is essential to periodically reassess paradigms. When RCC is diagnosed concurrently with another malignancy, the latter typically assumes priority in treatment. This scenario provides a unique opportunity to observe the effects of systemic therapy on the RCC, without incurring additional costs or risks to the patient. Our study aimed to explore the response of several "old school" and modern anti-cancer systemic therapies on growth rate of otherwise untreated RCC. Methods: Twenty patients (average age 61.4 years, SD 10.0 years) were diagnosed with histologically confirmed RCC and another type of cancer. These included lymphomas (7 patients), lung adenocarcinoma, and breast cancer (4 patients each), leukemia (3 patients), and 4 patients with other types of malignancy. The cohort received 29 different systemic chemotherapeutic agents, including cyclophosphamide and doxorubicin (5 patients each), and prednisone, vincristine, and rituximab (4 patients each). The patients were monitored radiographically, focusing on RCC, without any RCC-specific treatments. Changes in RCC diameter on axial CT scans were recorded during the follow-up period. Results: The average RCC diameter on initial CT scans was 41.9 ± 25.1 mm. After an average follow-up of 28.9 ± 29.6 months, the RCC diameter increased in 14 patients (by an average rate of 7.3 ± 2.9 mm/year), while it remained stable or decreased in six patients. Notably, tumor size reductions were observed in patients treated with Tamoxifen and a combination of bevacizumab, docetaxel, and cisplatin. Conclusions: These results underscore the significant resistance of RCC to both traditional chemotherapies and newer treatments, many of which have not been specifically evaluated in the context of RCC. However, several agents demonstrated potential efficacy and merit further investigation. Nevertheless, no solid conclusion can be drawn regarding any specific agent using this methodology.