RATIONALE: Androgens can stimulate the growth of prostate cancer cells. Hormone therapy using triptorelin may fight prostate cancer by reducing the production of androgens.

PURPOSE: Randomized phase III trial to compare the effectiveness of long-term hormone therapy and triptorelin with no further treatment in treating patients who have advanced prostate cancer previously treated with radiation therapy and 6 months of androgen suppression.

OBJECTIVES:

• Determine the best hormonal scheme to be associated with pelvic radiotherapy in the curative management of prostatic carcinoma for hormonal treatment with regards to treatment outcome (overall survival, clinical disease free survival, local regional control), quality of life (treatment side effects, sexual function), and health economy (cost effectiveness ratio).

OUTLINE: This is a randomized, multicenter study.

Patients receive external radiation for 5 weeks, followed by a pelvic boost given for 2 weeks and a 6 month combined androgen blockage initiated at the onset of external irradiation. Flutamide (Eulexin) or bicalutamide (Casodex) may be used as the antiandrogens. Antiandrogen treatment starts 1 week before the first injection of triptorelin.

Patients are then randomized to one of two treatment arms.

• Arm I: Patients receive no further treatment.
• Arm II: Patients receive antiandrogen for 2.5 years plus and LHRH analogue (triptorelin) administered every 3 months. Patients then continue the LHRH analogue alone for an additional 2.5 years in the absence of disease progression.

Patients are followed every 6 months for 5 years and then annually thereafter.

PROJECTED ACCRUAL: A total of 966 patients will be accrued over 5 years.

DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the prostate

  • T1c-T2a-b, N1-2 or pN1-2 (after pelvic lymphadenectomy)
  • T2c-T4, N0-2

• Prior external radiotherapy for locally advanced prostatic carcinoma required

• Prior hormone therapy (6 months of combined androgen blockade) for locally advanced prostatic carcinoma required with PSA no greater than 150 ng/mL before administration

• No progressive disease after the 6 months of combined androgen blockage

• No stages T1c/T2a-b with a negative pelvic lymph nodes status that is assessed clinically or surgically

• No lymph node involvement to common iliac and/or periaortic lymph nodes (M1a)

• No external iliac lymph node metastasis more than 5 cm in greatest dimension (N3)

• No distant metastases

PATIENT CHARACTERISTICS:

Age:

• Any age

Performance status:

• WHO 0-2

Life expectancy:

• At least 5 years

Hematopoietic:

• Hemoglobin at least 10 g/dL
• WBC at least 2,000/mm^3
• Platelet count at least 100,000/mm^3

Hepatic:

• Not specified

Renal:

• Not specified

Other:

• No prior or concurrent cancers other than basal cell skin cancer
• No serious nonmalignant disease resulting in a life expectancy of less than 5 years

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No prior biologic therapy for prostate cancer

Chemotherapy

• No prior chemotherapy for prostate cancer

Endocrine therapy

• See Disease Characteristics

Radiotherapy

• See Disease Characteristics

Surgery

• See Disease Characteristics