What is a nomogram:
- A type of prediction model
- Graphical calculating device which incorporates at least 2 variables, which can be continuous or categorical
- Each variable is given ‘risk points’ based on its prognostic significance
- The total ‘risk points’ is then used to estimate the outcome
Common nomograms prior to radical prostatectomy:
- MSKCC
- Briganti & updated ‘novel’ Briganti
- Partin tables
- Roach formula
MSKCC:
- Age, PSA, Gleason score, clinical stage, % positive cores
- Estimates LN+, SVI, ECE, prostate cancer specific survival, progression free probability after radical
Briganti 2017:
- PSA, clinical stage, ISUP grade, % positive cores with highest grade, % positive cores with lower grade cancer
Updated Briganti with MRI:
- PSA, clinical stage based on MRI, diameter of MRI lesion, ISUP grade, % cores with csPCa
- Gives estimates lymph node involvement
Partin tables:
- PSA, clinical stage, Gleason score
- Estimates EPE, LN+, SVI
Roach formula (historic)
What is the use in practice of nomograms:
- Do I need to do a lymph node dissection?
- EUA guidelines:
- An eLND should be performed in intermediate risk CaP if the estimate for LN+ exceeds 5 %
- Or > 7 % using new Briganti nomogram incorporating MRI guided biopsies
- In all other cases eLND can be omitted, which means accepting a low risk of missing positive nodes
- This cutoff results in missing only 1.5 % of patients with positive nodes
Limitations of nomograms:
- Developed using a single cohort, or a tertiary referral centre cohort
- May not be externally valid / applicable to all
- May become outdated quickly
- MRI, PSMA PET, active surveillance, different biopsy techniques
- Often based on systematic biopsies
- Can be over reliant on certain parameters
- g. over-reliance on clinical staging, when MRI shown to be more accurate
- Might be a useful tool but do not replace clinical judgement and individualised treatment