Yale formula (update of the Roach formula).
A new formula for prostate cancer lymph node risk
Many investigators have created tools for predicting extraprostatic disease and lymph node (LN) involvement. One widely used tool is a linear formula created by Roach et al. the Roach formula (RF), which defines the risk of pelvic LN as follows: (% pelvic LN risk = prostate-specific antigen [PSA])2/3 + (Gleason – 6))10). There has been significant stage migration in prostate cancer over the past decade since the creation of the RF. To provide clinicians with a practical approach to estimating LN risk that was developed from a population-based sample of patients who reflect the vast majority of patients diagnosed in the modern PSA era, and whose care reflects current patterns of care, we developed and validated a new predictive formula using the SEER database. A fast, accurate, and easy-to-use formula would be helpful in discussing LN risk with patients and in the conceptualization of LN risk for future clinical trials.
Research authors: James B. Yu, Danil V. Makarov, Cary Gross
Version: 1.10
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The calculated probability of lymph node involvement is: %

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Reported sensitivity is 39% and specificity is 94,9%.
Compared to the Roach Formula (RF) and Nguyen Formula (NF), our Yale Formula (YF) was able to classify the most patients in the high-risk (>15%) group while still maintaining good PPV and specificity. The YF had the best combination of sensitivity with high specificity and did not underestimate LN risk as the NF did. Underestimation of LN risk is potentially more harmful than overestimation of risk if patients are counseled to undergo prostate-only therapy based on an underestimation of risk, whereas they could potentially undergo pelvic LN irradiation with a chance at improving subsequent pelvic and cure rates. The utility of pelvic radiotherapy remains controversial, but it stands to reason that pelvic radiotherapy should be given more often to patients at higher risk for LN metastases than to those who are at lower risk.

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