What happened at the ASCO meeting today (Saturday)

From a prostate cancer perspective, the “main event” today was the genitourinary (prostate) cancer poster session in the afternoon, focused on the treatment of advanced and high-risk disease.

A total of 24 posters were presented in this session, and most of these posters offered little really new information for the vast majority of patients. However, a small number of these posters are worth calling out, along with links to the relevant abstracts.

Morris et al. (abstract no. 5022) presented early safety data from their randomized, open-label, multicenter, Phase III study of androgen deprivation with leuprolide acetate + 30 days of bicalutamide with or without docetaxel chemotherapy in men with clinically asymptomatic prostate cancer and a rising PSA following definitive local therapy (surgery alone or surgery + salvage radiation therapy). The full results of this study (i.e., the impact on progression-free survival at 18 months of follow-up) are still unknown, but the data presented did show that ADT for 18 months ± docetaxel for 10 cycles can be given with reasonable safety to pre-metastatic, castration-sensitive prostate cancer patients. Men who received docetaxel in this study had levels of toxicity that were in concordance with the known Toxicity profile for docetaxel. The trial enrolled just over 400 patients, and so it should be large enough to tell us whether adding docetaxel to ADT as a rescue regimen after first-line surgery or surgery + salvage radiation. This study may be important, given that we still don;t know the optimal approach to treatment of prostate cancer patients who relapse biochemically after a radical prostatectomy.

Results presented by Hurwitz et al. (abstract no. 5031), from the RTOG 0621 trial of adjuvant radiation, androgen deprivation, and docetaxel for high-risk prostate cancer post-prostatectomy, seem to have produced a positive result in such high-risk patients. This was only a small trial that enrolled 76 eligible patients with a median age of 62 years.  However, the 3-year rate of freedom from progression was 71 percent (which was statistically significant). There were two deaths in this study, of which one was directly elated to prostate cancer. Common side effects associated with chemotherapy included peripheral neuropathy (12 Grade 2 and one Grade 3) and febrile neutropenia in 3 patients. Six patients (8 percent) experienced late Grade 3 or Grade 4 treatment-related toxicities. The authors concluded that the addition of ADT and docetaxel to adjuvant radiation therapy for men at high-risk of failure despite ART alone following prostatectomy resulted in a significant improvement in freedom from biochemical progression as compared to historical controls. They further concluded that Phase III trials assessing chemotherapy in this high-risk population are warranted.

The remainder of the studies presented today provided evolving information about the use of a variety of newer agents like abiraterone, enzalutamide, ARN-509, and others alone and in combination with other drugs in late stage disease. None of these studies were large enough or important enough to give us definitive information about the appropriate use of these agents, but in some cases they provide clear evidence that specific combinations of drug can be given together.

We knew before the start of the ASCO meeting that much of the data to be presented this year would be of limited, immediate, clinical significance. That has been playing out in the presentations to date. However, it also suggests that there may be more important data to come about combination therapy for late stage disease in the next couple of years.

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