Notes on high prediction numbers at high Gleason Score

During the last meeting, we discussed the fact that some values seem really high.
When the Gleason Score is greater than 8, it appears for few values of Clinical stage and PSA that the chance for the cancer to be organ confined is higher than with a lower Gleason Score.

After another look at Makarov et al. (2007) paper, I noticed that they also had unexpected results when the Gleason Score was greater than 8:

The second change is a previously undescribed phenomenon: a seemingly paradoxical improvement of pathologic stage predictions in men with GS 8 to 10 versus GS 4 + 3. For GS 8 to 10, in every combination of PSA level and clinical stage, the predicted probability of OC was somewhat higher than in GS 4 + 3. A calibration plot for the model demonstrated that the modeled predicted probabilities of OC were very close to observed values (data not shown). In counseling patients, it is important to relay that patients with GS 8 to 10 in this series were carefully selected; 75% of them had been cleared for surgery with negative results on metastatic workup. The predictions from this nomogram do not apply to all patients with high-grade cancer. The Partin tables and other nomograms relating to men with GS 8 to 10 who have undergone RP represent best-case scenarios of a select few, carefully screened patients with
limited, high-grade cancer on biopsy and no evidence of metastasis on radiographic imaging.