A phase 2 study of surveillance in patients with metastatic renal cell carcinoma and assessment of response of such patients to therapy on progression.

Following preliminary studies suggesting that some patients with metastatic renal cell carcinoma had accelerated tumor growth after entry into chemotherapy studies, 73 patients with measurable metastatic disease referred to a tertiary referral center for consideration for experimental treatment protocol have been observed to attempt to establish the incidence of spontaneous regression. Initially, patients went off study if metastases showed greater than 25% increase in products of bidimensional measurement but with increasing confidence patients only went into therapy protocols with the development of symptomatic progression. In this selective series, on observation, three complete (histologically documented) and two partial unexplained "spontaneous" regressions were observed and a further four patients had prolonged stable disease for more than 12 months. On progression, 52 were entered into treatment protocols (BCG n = 19, Mitozantrone n = 12, and Welferon n = 21). A further two complete and five partial responses (14%) and four prolonged stable disease were observed confirming that the previously reported responses with these agents are not totally explicable on the basis of "spontaneous" response.