Elective Pelvic Lymph Node Dose in Prostate Cancer
For high-risk prostate cancer patients receiving pelvic lymph node irradiation, the elective nodal dose should be 45-50.4 Gy using conventional fractionation, delivered concurrently with dose-escalated treatment to the prostate (75-80+ Gy). 1
Standard Elective Nodal Dosing
The NCCN guidelines recommend 44-50 Gy to the pelvic lymph nodes when treating high-risk prostate cancer patients. 1
This elective dose is delivered to areas at risk for microscopic nodal involvement, including the obturator, internal and external iliac, presacral, and sacral lymph node regions. 1
The elective nodal volume receives this lower dose while the prostate itself receives the higher definitive dose of 75.6-81 Gy, typically using IMRT techniques. 1
Risk-Stratified Approach to Nodal Irradiation
High-Risk Disease
Pelvic lymph node irradiation is a Category 1 recommendation for high-risk prostate cancer patients, combined with 24-36 months of androgen deprivation therapy. 1, 2
High-risk features include: T3-T4 disease, Gleason score 8-10, or PSA >20 ng/mL. 1
Intermediate-Risk Disease
Pelvic nodal irradiation may be considered for intermediate-risk patients, though it is not mandatory. 1
When used, the same elective dose of 44-50 Gy applies, with 4-6 months of concurrent ADT. 1
Low-Risk Disease
- Patients with low-risk prostate cancer should NOT receive pelvic lymph node irradiation. 1
Dose Escalation Considerations
Emerging Evidence for Higher Nodal Doses
Recent prospective data suggests that moderate dose escalation to 56 Gy to pelvic nodes (delivered simultaneously with 70 Gy to the prostate in 28 fractions) is feasible and well-tolerated, with 80.2% biochemical control at 6.4 years median follow-up. 3
This approach used a simultaneous integrated boost technique with IMRT, showing only 1 acute grade 3 toxicity among 30 patients. 3
However, this remains investigational and is not yet standard practice. The conventional 45-50.4 Gy remains the guideline-recommended dose. 1
Technical Delivery Methods
When combining hypofractionated prostate treatment (2.5 Gy/fraction) with elective nodal irradiation, the nodes can receive 56 Gy in 2 Gy fractions concurrently while the prostate receives 70 Gy. 4
Conformal avoidance-based IMRT techniques that specifically exclude bowel, rectum, and bladder allow safe delivery of these doses. 4
Critical Toxicity Considerations
Increased Gastrointestinal Toxicity
Adding elective nodal irradiation to hypofractionated prostate radiotherapy significantly increases both acute (37% vs 17%, p=0.001) and late GI toxicity (15.3% vs 5.3% at 3 years, p=0.026). 5
The addition of pelvic nodal fields appears to sensitize the rectum to hot spots, making rectal V70 >3 cc particularly problematic. 5
When using elective nodal irradiation, extra caution must be taken to minimize the volume of rectum receiving 100% of the prescription dose. 5
Image Guidance Requirements
Daily image-guided radiation therapy (IGRT) is essential when delivering doses >75 Gy to the prostate to ensure accuracy and minimize toxicity. 1, 2
IGRT techniques include CT, ultrasound, implanted fiducials, or electromagnetic tracking. 1
Common Pitfalls to Avoid
Do not use the standard 45-50 Gy nodal dose as a boost dose to grossly involved nodes—these require higher doses of 54-66 Gy if anatomically feasible. 1
Avoid treating pelvic nodes in low-risk patients, as this adds toxicity without oncologic benefit. 1
When using simultaneous integrated boost techniques, ensure the planning system correctly accounts for different fractionation schemes to the prostate versus nodes. 4, 3
Restrict small bowel volume receiving ≥45 Gy to ≤300 mL to minimize acute toxicity. 4