RATIONALE: Giving samarium Sm 153 lexidronam pentasodium and 3-dimensional (3-D) conformal radiation therapy or intensity-modulated radiation therapy may keep prostate cancer from growing in patients with rising prostate-specific antigen (PSA) levels after radical prostatectomy for prostate cancer.

PURPOSE: This phase II trial is studying how well samarium Sm 153 lexidronam pentasodium and 3-D conformal radiation therapy or intensity-modulated radiation therapy work in treating patients with rising PSA levels after radical prostatectomy for prostate cancer.

OBJECTIVES:

Primary

• To assess the effectiveness of samarium Sm 153 lexidronam pentasodium (as determined by a 30% decline in the PSA level within 12 weeks) followed by either three-dimensional conformal radiation therapy or intensity-modulated radiation therapy in patients with rising prostate-specific antigen levels (PSA) after radical prostatectomy prostate cancer.

Secondary

• To assess the proportion of patients completing protocol treatment.
• To evaluate hematological toxicity at 12 weeks.
• To evaluate samarium Sm 153 lexidronam pentasodium-related adverse events at 12 weeks.
• To evaluate the "acute" and "late" radiation therapy-related events having occurred up to 24 weeks from the end of radiation therapy.
• To compare the freedom from progression rate at 2 years to that predicted by the Kattan Nomograms.

OUTLINE: Patients receive samarium Sm 153 lexidronam pentasodium (SM) IV on day 1. Patients are closely monitored for prostate-specific antigen (PSA) level and SM-associated toxicity for 12 weeks. After the 12 weeks, patients undergo either intensity-modulated radiation therapy or 3-dimensional conformal radiation therapy 5 days a week for 7-8 weeks. Patients may receive hormonal therapy (after radiation therapy) at the discretion of their physician.

Treatment continues in the absence of disease progression (defined as a PSA doubling time less than 3 months), severe thrombocytopenia (defined as a platelet count of 25,000 cells/mm³ or less), or unacceptable toxicity.

After completion of study treatment, patients are followed up at 3 months, 6 months, and 12 months, every 6 months for 2 years, and then annually thereafter.

DISEASE CHARACTERISTICS:

Inclusion criteria:

• Histologically proven diagnosis of prostate cancer progressing after prior radical prostatectomy as indicated by one of the following:

  • Postoperative prostate-specific antigen (PSA) rising above 1.0 ng/mL
  • Postoperative PSA rising above 0.2 ng/mL with a surgical tumor Gleason score of 9 or 10
  • Postoperative PSA rising above 0.2 ng/ml with nodal disease

• Stage II-IV disease (T2 -T4, N0-N1)

• No distant metastases based on the following minimum diagnostic work up:

  • History or physical examination within the past 8 weeks
  • Bone scan negative for bone metastases within the past 4 months
  • Abdominal imaging negative for metastases within the past 6 months

Exclusion criteria:

• Biopsy evidence of M1 disease
• Presence of neuroendocrine features in any prostate cancer specimen

PATIENT CHARACTERISTICS:

Inclusion criteria:

• Zubrod Performance Status 0-1
• Absolute neutrophil count (ANC) ≥ 1,800 cells/mm³
• Platelet count ≥ 100,000 cells/mm³
• Hemoglobin ≥ 8.0 g/dL (transfusion or other intervention to achieve Hgb ≥ 8.0 g/dl is permitted)

Exclusion criteria:

• Prior invasive malignancy (except nonmelanoma skin cancer) unless disease free for a minimum of 3 years

• Severe, active comorbidity, defined as follows:

  • Unstable angina and/or congestive heart failure requiring hospitalization within the last 6 months
  • Transmural myocardial infarction within the last 6 months
  • Acute bacterial or fungal infection requiring intravenous antibiotics at the time of registration
  • Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects (laboratory tests for liver function and coagulation parameters, however, are not required for entry into this protocol)
  • Renal failure (laboratory tests for renal function, however, are not required for entry into this protocol)
  • AIDS based upon current Centers for Disease Control (CDC) definition (HIV testing is not required)

PRIOR CONCURRENT THERAPY:

• No prior systemic chemotherapy for the study cancer

  • Prior chemotherapy for a different cancer is permitted

• No hormonal therapy initiated within the last 3 months

• No prior radiotherapy to the pelvic region that would result in overlap of radiotherapy fields

PI's are required to abide by the sponsor's publication guidelines which require review by coauthors and subsequent review and approval by the sponsor.