Residency · Residency · Radiation Oncology
Prostate Cancer: Adjuvant vs. Salvage Radiation After Prostatectomy
Introduction
After radical prostatectomy for prostate cancer, approximately 30-40% of men will experience biochemical recurrence (BCR), indicated by a rising prostate-specific antigen (PSA) level. A major clinical question in genitourinary oncology has been whether to administer radiation therapy immediately after surgery (adjuvant radiation) or to wait until PSA levels rise (salvage radiation). Three landmark randomized trials have demonstrated that early salvage radiation, initiated at low PSA levels, achieves oncologic outcomes equivalent to adjuvant radiation while sparing many patients from unnecessary treatment.
Definitions
Adjuvant radiation therapy (ART) refers to radiation delivered within 4 to 6 months after prostatectomy, before any evidence of biochemical recurrence, typically based on adverse pathologic features found during surgery. Salvage radiation therapy (SRT), on the other hand, is given at the time of biochemical recurrence, which is defined by a detectable and rising PSA, usually triggered when PSA reaches 0.1 to 0.2 ng/mL. Biochemical recurrence post-prostatectomy is specifically defined as a PSA level of 0.2 ng/mL or higher, confirmed by a subsequent rising value.
Adverse Pathologic Features Prompting Consideration of Post-Prostatectomy RT
Certain adverse pathologic features after prostatectomy prompt consideration of post-operative radiation therapy. The most common indication is positive surgical margins, where cancer cells are found at the edge of the removed tissue. Other features include extraprostatic extension (classified as pT3a), seminal vesicle invasion (pT3b), and a high Gleason Grade Group of 4 or 5. Additionally, a detectable or rising post-operative PSA level also warrants consideration of radiation.
Landmark Adjuvant Trials (Historical Context)
Several early randomized trials established the rationale for post-prostatectomy radiation. The SWOG 8794 trial compared adjuvant radiation therapy (60-64 Gy) to observation in patients with pT3 or margin-positive disease, showing improved metastasis-free survival and overall survival at 15 years with adjuvant radiation. The EORTC 22911 trial also compared adjuvant radiation to a wait-and-see approach in a similar patient population, demonstrating improved biochemical progression-free survival but no overall survival benefit at 10 years. The ARO 96-02 trial, with a similar design, confirmed the biochemical progression-free survival benefit of adjuvant radiation but did not show a difference in overall survival.
The Modern Adjuvant vs. Early Salvage Trials
More recent trials have focused on comparing adjuvant radiation to early salvage radiation initiated at low PSA thresholds. The RADICALS-RT trial, the largest to date with 1,396 patients, randomized men to adjuvant radiation versus salvage radiation triggered at PSA ≥ 0.1 ng/mL. It found no difference in biochemical progression-free survival at 5 years, and the salvage approach spared 60% of patients from radiation. The GETUG-AFU 17 (RAVES) trial compared adjuvant radiation to early salvage radiation triggered at PSA ≥ 0.2 ng/mL and demonstrated non-inferior event-free survival with the early salvage approach. Similarly, the TROG 08.03 (RAVES) trial confirmed the non-inferiority of early salvage radiation compared to adjuvant radiation. A combined meta-analysis of these three trials, known as ARTISTIC, concluded that early salvage radiation is non-inferior to adjuvant radiation for event-free survival and that adjuvant radiation results in overtreatment for a substantial proportion of patients.
Salvage Radiation: Practical Considerations
Salvage radiation should be initiated at the earliest sign of biochemical recurrence, typically when PSA reaches 0.1 to 0.2 ng/mL. Outcomes strongly correlate with the PSA level before salvage radiation, with lower PSA levels associated with better results. The National Comprehensive Cancer Network (NCCN) recommends offering salvage radiation at PSA ≥ 0.1 ng/mL and ideally before PSA exceeds 0.5 ng/mL. The typical prostate bed radiation dose ranges from 64 to 72 Gy, delivered in 1.8 to 2.0 Gy fractions, with dose escalation to 70-72 Gy now preferred based on the SAKK 09/10 trial. The clinical target volume (CTV) for salvage radiation includes the prostate bed, delineated using surgical clips, pre-operative imaging, and consensus guidelines. Pelvic lymph node irradiation is considered for patients with high-risk features, as supported by the SPPORT trial.
The SAKK 09/10 trial compared 64 Gy versus 70 Gy for salvage radiation and found that 70 Gy improved freedom from biochemical progression, supporting dose escalation in the salvage setting. The SPPORT trial (NRG-GU002) was a three-arm study comparing prostate bed radiation alone, prostate bed plus short-term androgen deprivation therapy (ADT), and prostate bed plus pelvic nodes plus short-term ADT. The combination of prostate bed radiation with pelvic nodal irradiation and ADT improved freedom from progression compared to prostate bed radiation alone, supporting the inclusion of pelvic nodal coverage in appropriate patients.
Role of ADT with Post-Prostatectomy Radiation
The addition of androgen deprivation therapy (ADT) to salvage radiation has been studied in several trials. The GETUG-16 trial evaluated salvage radiation with or without 6 months of goserelin and found that short-term ADT improved biochemical-free survival and metastasis-free survival. The RTOG 9601 trial assessed salvage radiation with or without 24 months of bicalutamide 150 mg and demonstrated that long-term ADT improved overall survival and metastasis-free survival, particularly in patients with PSA levels ≥ 0.7 ng/mL. The benefit of ADT was marginal or absent in patients with very low pre-salvage radiation PSA. Practically, short-term ADT (4-6 months) is generally recommended with salvage radiation, with longer durations considered for patients with high-risk features such as high Gleason grade, seminal vesicle invasion, or elevated pre-salvage PSA.
| Trial | Comparison | Key Finding |
|---|---|---|
| RADICALS-RT | Adjuvant RT vs. salvage RT (PSA ≥ 0.1) | No difference in bPFS; 60% spared RT |
| GETUG-AFU 17 | Adjuvant RT vs. early salvage (PSA ≥ 0.2) | Non-inferior event-free survival |
| TROG 08.03 (RAVES) | Adjuvant RT vs. early salvage (PSA ≥ 0.2) | Non-inferior freedom from progression |
| ARTISTIC meta-analysis | Combined analysis of above 3 trials | Early salvage non-inferior to adjuvant |
| SAKK 09/10 | Salvage 64 Gy vs. 70 Gy | 70 Gy improved biochemical control |
| SPPORT (NRG-GU002) | Prostate bed ± pelvic nodes ± ADT | PB + pelvic nodes + ADT improved FFP |
| GETUG-16 | Salvage RT ± 6 mo ADT (goserelin) | Short ADT improved bPFS and MFS |
| RTOG 9601 | Salvage RT ± 24 mo bicalutamide | Long ADT improved OS (benefit at PSA ≥ 0.7) |
Genomic Classifiers in the Post-Prostatectomy Setting
Genomic classifiers, such as the Decipher test, are increasingly used to stratify patients after prostatectomy. High Decipher scores identify patients who may benefit from intensified treatment, including ADT and pelvic nodal radiation. Conversely, low Decipher scores may support observation even in the presence of adverse pathologic features. This genomic information helps personalize decisions regarding adjuvant or salvage radiation therapy.
Key Clinical Pearls
The ARTISTIC meta-analysis has confirmed that early salvage radiation is non-inferior to adjuvant radiation, supporting a salvage approach for most patients with adverse pathologic features. Salvage radiation should be initiated at the earliest sign of biochemical recurrence, typically when PSA reaches 0.1 to 0.2 ng/mL, as outcomes are strongly dependent on PSA levels. Dose escalation to 70 Gy, as demonstrated in the SAKK 09/10 trial, and pelvic nodal coverage combined with short-term ADT, as supported by the SPPORT trial, are now standard considerations in the salvage setting. Finally, genomic classifiers such as Decipher provide valuable information to personalize the intensity of post-prostatectomy treatment.
References
- Parker CC, Clarke NW, Cook AD, et al. Timing of radiotherapy after radical prostatectomy (RADICALS-RT): a randomised, controlled phase 3 trial. Lancet. 2020;396(10260):1413-1421.
- Vale CL, Fisher D, Kneebone A, et al. Adjuvant or early salvage radiotherapy for the treatment of localised and locally advanced prostate cancer: a prospectively planned systematic review and meta-analysis of aggregate data. Lancet. 2020;396(10260):1422-1431.
- Pollack A, Karrison TG, Balogh AG, et al. The addition of androgen deprivation therapy and pelvic lymph node treatment to prostate bed salvage radiotherapy (NRG Oncology/RTOG 0534 SPPORT). Int J Radiat Oncol Biol Phys. 2022;112(1):18-30.
- Tendulkar RD, Agrawal S, Gao T, et al. Contemporary Update of a Multi-Institutional Predictive Nomogram for Salvage Radiotherapy After Radical Prostatectomy. J Clin Oncol. 2016;34(30):3648-3654.