High-risk localized prostate cancer: a case for early chemotherapy

High-risk tumors exhibit a more aggressive natural history and have higher positive margin and recurrence rates after radical prostatectomy or radiotherapy alone, where unimodality therapy likely represents undertreatment. Hence, the therapeutic ratio (patients who actually realize a survival benefit from a therapeutic intervention) may, therefore, be greater in high-risk disease if its natural history can be altered by multimodality therapy. It is, thus, important to investigate therapies that optimize complete extirpation of all cancer cells and reduce the incidence of positive surgical margins and disease recurrence. Neoadjuvant therapy extends the logic of early adjuvant therapy further by applying systemic therapy earlier in the course of the disease before definitive locoregional therapy. In prostate cancer, outcomes have not been improved significantly when neoadjuvant hormone therapy is used before surgery; although outcomes are improved when androgen ablation is combined with radiotherapy, many patients remain at risk for systemic recurrence. With recent data confirming improved survival data with docetaxel chemotherapy in metastatic disease, future trials are now focusing on earlier combinations of chemohormonal or biologic therapies in high-risk patients.

Timing Is Everything: Preclinical Evidence Supporting Simultaneous Rather Than Sequential Chemohormonal Therapy for Prostate Cancer

PURPOSE

Androgen ablation is the mainstay of systemic therapy for prostate cancer, with cytotoxic therapies reserved for hormone-refractory disease. It is not clear, however, that this is the most appropriate sequence of interventions for this disease. This study addresses the ideal timing of systemic treatments in the Shionogi and LNCaP xenograft models. We explored the hypothesis that stress-induced gene expression changes after chemotherapy can induce a hormone-independent phenotype.

EXPERIMENTAL DESIGN

Three groups of mice bearing either Shionogi or LNCaP xenografts were treated with (a) initial castration and delayed paclitaxel, (b) initial paclitaxel and delayed castration, or (c) simultaneous castration plus paclitaxel. End points were time to tumor progression and time to sacrifice. Microarray and reverse transcription-PCR analyses were carried out to assess changes in gene expression induced by paclitaxel.

RESULTS

Mice receiving simultaneous therapy showed a significant improvement in median time to progression (TTP: Shionogi, 65 versus 38 days, P = 0.004; LNCaP, 105 versus 70 days, P = 0.032) and time to sacrifice (Shionogi, 83 versus 66 days, P < 0.014) versus best sequential therapy. A marked lack of response to castration was observed after initial paclitaxel therapy. Gene expression and reverse transcription-PCR studies confirmed that several genes known to play a role in androgen independence were up-regulated in response to paclitaxel exposure.

CONCLUSIONS

In laboratory models of prostate cancer, simultaneous androgen deprivation plus paclitaxel is more effective than sequential treatments. These findings provide preclinical proof-of-principle for ongoing clinical trials addressing the role and timing of systemic therapies in prostate cancer.