Roach formula (Lymph Node involvement)
A simple equation for estimating the risk of positive lymph nodes was empirically derived from a nomogram published by Partin et al. demonstrating the value of combining the pre-treatment prostate specific antigen and Gleason Score in predicting the risk of lymph node metastasis for patients with clinically localized prostate cancer. The risk of positive nodes (NS) was calculated using the equation; N+ = (2/3*PSA) + (GS - 6) X 10, where PSA and GS are the pre-treatment prostate specific antigen and Gleason Score respectively, and the calculated risk is constrained between O-65% for a PSA < 40 ng/ml (as in the nomogram).
Research authors: Mack Roach III, Carol Marquez, Hae-Sook Yuo, Perinchery Narayan, Lorie Coleman, Unyime O. Nseyo, Zarrin Navvar, Peter R. Carrol
Version: 1.8
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Calculated risk for Lymph Node Involvement is: %

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The predicted risk on pelvic lymph node invasion supports decision making regarding the performance of a pelvic lymph node dissection in patients with prostate cancer patients. Patients at low risk of lymph node metastases can be spared from surgical removal of the lymph nodes. 

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