Radiation Therapy in Treating Patients With Relapsed Prostate Cancer After Surgery

DISEASE CHARACTERISTICS: * Diagnosis of adenocarcinoma of the prostate * Lymph node negative disease * Stage pT2a-3b; R0-1; pN0 or cN0 * Undergone a radical prostatectomy ≥ 12 weeks prior to randomization * PSA progression after prostatectomy defined as two consecutive rises with the second rising value \> 0.1 ng/mL OR three consecutive rises (the first value must be measured 4 weeks after radical prostatectomy) * PSA ≤ 2 ng/mL at randomization * No persistent PSA \> 0.4 ng/mL, 4-20 weeks after radical prostatectomy * No palpable prostatic fossa mass suggestive of recurrence, unless an ultrasound-guided biopsy is non-malignant * No pre-salvage radiotherapy pelvic lymph node enlargement \> 1 cm in short axis diameter of the abdomen and pelvis (cN1) (unless the enlarged lymph node is sampled and negative) * No evidence of macroscopic local recurrence or metastatic disease on pre-salvage radiotherapy MRI (with IV contrast) or multislice computed tomography (with IV and oral contrast) of the abdomen and pelvis assessed within 16 weeks prior to randomization * No presence or history of bone metastases (bone scan must be performed in case of clinical suspicion \[e.g., bone pain\]) * Gleason score must be available PATIENT CHARACTERISTICS: * WHO performance status 0-1 * Fertile patients must use effective contraception during and for 6 months after completion of study therapy * Compliant and geographically proximal to allow for proper staging and follow-up * No prior invasive malignancy, except non-melanomatous skin cancer or other malignancies with a documented disease-free survival of ≥ 5 years * No bilateral hip prosthesis * No severe or active co-morbidity likely to impact on the advisability of dose-intensive salvage radiotherapy, including any of the following: * History of inflammatory bowel disease * Acute bacterial or fungal infection requiring intravenous antibiotics at the time of randomization * Unstable angina and/or congestive heart failure requiring hospitalization within the past 6 months * Transmural myocardial infarction within the past 6 months * Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy at the time of randomization * No psychiatric disorder precluding understanding of information on trial-related topics, giving informed consent, or filling out quality-of-life questionnaires PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior pelvic radiotherapy * No hormonal treatment or bilateral orchiectomy prior to or following prostatectomy * At least 4 weeks since prior and no concurrent use of products known to affect PSA levels (e.g., PC Calm, PC Plus, PC SPES, finasteride, or fluconazole) * At least 30 days since prior treatment in another clinical trial * No other concurrent anticancer treatments, including luteinizing hormone-releasing hormone (LHRH) analogues, antiandrogens, orchiectomy, or chemotherapy * No other concurrent investigational or experimental treatments or drugs INCLUSION CRITERIA * Patient must give written informed consent before randomization. * Lymph node negative adenocarcinoma of the prostate treated with radical prostatectomy at least 12 weeks before randomization. Tumor stage pT2a-3b, R0-1, pN0 or cN0 according to the UICC TNM 2009 (see Appendix 1), Gleason score available. * PSA progression after prostatectomy defined as two consecutive rises with the final PSA \> 0.1 ng/mL or three consecutive rises. The first value must be measured earliest 4 weeks after radical prostatectomy. * PSA at randomization ≤ 2 ng/mL. * WHO performance status 0-1 at randomization. * Age at randomization between 18 and 75 years. * Baseline QoL questionnaire (QLQ) has been completed. * Patient agrees not to father a child during salvage RT and during 6 months thereafter. * Patient compliance and geographic proximity allow proper staging and follow-up. * The responsible pathologist has agreed to provide sample material for central pathological review (see Section 16) and tissue banking (only if patient gave informed consent) within the specified timelines. EXCLUSION CRITERIA * Persistent PSA 4-20 weeks after radical prostatectomy \> 0.4 ng/mL * Palpable prostatic fossa mass suggestive of recurrence, unless an ultrasound guided biopsy is non-malignant. * Pre-salvage RT pelvic lymph node enlargement \> 1 cm in short axis diameter of the abdomen and pelvis (cN1), unless the enlarged lymph node is sampled and negative, and/or evidence of macroscopic local recurrence or metastatic disease on pre-salvage RT MRI (magnetic resonance imaging; with i.v. contrast) or multislice computed tomography (CT; with i.v. and oral contrast) of the abdomen and pelvis assessed within 16 weeks prior to randomization. * Presence or history of bone metastases. Bone scan must be performed in case of clinical suspicion (e.g. bone pain). * Prior invasive malignancy, except non-melanomatous skin cancer or other malignancies with a documented disease-free survival for a minimum of 5 years. * Hormonal treatment or bilateral orchiectomy prior to or following prostatectomy. * Bilateral hip prosthesis. * Prior pelvic radiotherapy. * The use of products known to affect PSA levels within 4 weeks prior to start of trial treatment (e.g. PC Calm, PC Plus, PC SPES, finasteride, fluconazole). * Severe or active co-morbidity likely to impact on the advisability of dose intensified salvage RT. * Psychiatric disorder precluding understanding of information on trial related topics, giving informed consent or filling out QoL questionnaires. * Concurrent treatment with other experimental drugs or other anti-cancer therapy, treatment in a clinical trial within 30 days prior to trial entry.