Probability of remaining recurrence-free after salvage radiation

In 2007, Stephenson et al. published a nomogram that predicted the probability of success of salvage radiation after post-prostatectomy biochemical failure. Biochemical failure was defined as a PSA≥0.2 ng/ml. Memorial Sloan Kettering Cancer Center has made the nomogram publicly available at this link. But that data was put together before ultrasensitive PSA tests became widely available, and before three randomized clinical trials demonstrated an advantage to adjuvant radiation over waiting. Several studies now suggest (see this link) that early salvage may provide the same benefit as adjuvant radiation therapy, but with less risk of overtreatment.

Tendulkar et al. have now updated the Stephenson nomogram.. The original nomogram was based on 1,540 patients treated between 1987 and 2005 at 17 tertiary care facilities. All patients had a confirmed PSA ≥0.2 ng/ml before SRT. Outcomes were based on 6-year progression-free probability after SRT. The updated nomogram is based on 2,460 patients treated between 1987 and 2013 at 10 academic medical centers. It included post-op ultrasensitive PSA test results for some (18 percent) of the patients, but only 18 patients were treated at a PSA≤0.05 ng/ml. The nomogram predicts 5- and 10-year probability of freedom from biochemical failure (PSA≥0.2 ng/ml) after SRT. The authors also constructed a nomogram that predicts 5- and 10-year probability of incidence of metastasis. Their model has a predictive accuracy of about 68 percent for freedom from biochemical failure, and 74 percent for incidence of metastasis.

Update (3/27/2018): Cleveland Clinic now has a more convenient online version of this nomogram on their website:
http://riskcalc.org/ProstateCancerAfterRadicalProstatectomyNew/

The tables below approximate the nomogram for predicting the 10-year probability of remaining free of biochemical failure after SRT treatment.

Risk Factor	Score (points)	Points
ADT	Yes: 0      No: 49
Gleason score	6: 0      7: 54        8: 70        9/10: 90
Extraprostatic Extension	No:0        Yes:22
Surgical Margins	Positive: 0         Negative: 27
Seminal Vesicle Invasion	No: 0      Yes: 24
Pre-RT PSA (ng/ml)	0.05: 2.5    0.1: 5   0.2:10    0.3: 15        0.5: 25     1.0: 50   1.5: 75
Radiation dose (Gy)	≥66 Gy: 0   <66 Gy: 17
Total points

Total points	Probability
100	70%
150	50%
195	30%
220	20%
245	10%
265	5%

As an example, take the case of a man who, after his prostatectomy, had a Gleason score of 9 (=90 points), seminal vesicle invasion (=24 points), margins were negative (=27 points), PSA before SRT was 0.5 ng/ml (=25 points), and his radiation oncologist plans on treating him with a dose of 65 Gy (=17 points) without ADT(=49 points). His total score is 90+24+27+25+17+49= 232. This corresponds to about a 15% probability of success. The doctor and his patient probably would not consider this SRT treatment, given the risk of adverse side effects.

Now, let’s suppose the same man is treated earlier when his PSA is only 0.05 ng/ml (2.5 points) and his radiation oncologist proposes a dose of 70 Gy (=0 points) with ADT beginning two months before SRT (=0 points). His total score is 90+24+27+2.5+0+0= 143.5. This corresponds to about a 55% probability of success. This SRT treatment is a lot more tempting.

Because of database limitations, they could not incorporate PSA doubling time or increases in their model. They also could not include the duration of ADT use or more precise radiation dosage. With more data, a genomic classifier (Decipher®) also might improve the predictive accuracy of their model. Together with other factors like co-morbidities, risk of adverse effects and life expectancy, this nomogram should prove useful in helping the patient and doctor decide whether SRT is worthwhile.


Note: Thanks to Dr. Rahul Tendulkar for providing me with the full text of his original article.