Phase I study of concurrent weekly docetaxel, high-dose intensity-modulated radiation therapy (IMRT) and androgen-deprivation therapy (ADT) for high-risk prostate cancer.

UNLABELLED: Study Type - Therapy (phase 1) Level of Evidence 2a What's known on the subject? and What does the study add? High-risk and locally advanced prostate cancers are difficult to cure with the standard regimen of radiation therapy (RT) with concurrent androgen-deprivation therapy (ADT). Multiple studies have explored the addition of docetaxel chemotherapy in attempt to improve patient outcomes. Prior Phase I studies have shown that docetaxel 20 mg/m(2) is a safe dose, when given concurrently with 70 Gy of radiation. But current standard RT for prostate cancer uses higher doses, and it is unclear if concurrent chemotherapy is safe with modern RT. This is a Phase I study that explored the addition of concurrent docetaxel chemotherapy to modern RT (intensity-modulated RT to 78 Gy) plus ADT. The study showed that weekly docetaxel at 20 mg/m(2) is safe with modern RT. At a median follow-up of 2.2 years, biochemical progression-free survival was 94%. This triple-therapy regimen is safe and promising for further evaluation in prospective trials.

OBJECTIVE: •  To evaluate in a phase I trial, the feasibility of adding concurrent weekly docetaxel chemotherapy to high-dose intensity modulated radiation therapy (IMRT) and androgen-deprivation therapy (ADT) for treatment of high-risk prostate cancer.

PATIENTS AND METHODS: •  Patients with high-risk prostate cancer were treated with a luteinising hormone-releasing hormone agonist (starting 2-3 months before IMRT and lasting 2 years), IMRT of 78 Gy to the prostate and seminal vesicles, and weekly docetaxel during RT. •  All patients had computed tomography and bone scans to exclude metastatic disease. •  A standard 3 + 3 design was used for docetaxel dose escalation. Successive patients were treated on dose levels of 10, 15, and 20 mg/m(2) of weekly docetaxel.

RESULTS: •  In all, 18 patients participated in the study: 15 (83%) had Gleason 8-10 disease; the other three had either clinical T3 disease and/or a prostate-specific antigen (PSA) level of >20 ng/mL. •  Grade 3 diarrhoea (a defined dose-limiting toxicity, DLT) occurred in one patient in each of the first two dose levels. However, when the cohorts were expanded, no further DLT was seen. •  Weekly docetaxel at 20 mg/m(2) (dose level 3) was successfully given without DLT. •  No patient had grade 4 or 5 toxicity. •  At a median follow-up of 2.2 years, all patients achieved a PSA nadir of <1 ng/mL, including 13 patients who had an undetectable PSA level. The 2-year biochemical progression-free survival was 94%.

CONCLUSION: •  A dose of 20 mg/m(2) of weekly docetaxel given concurrently with high-dose IMRT and ADT appears safe for further study in patients with high-risk prostate cancer.