On the probability of lymph node negativity in pN0-staged prostate cancer—a theoretically derived rule of thumb for adjuvant needs

• Published in: Strahlentherapie und Onkologie Vol. 198; no. 8; pp. 690 - 699
• Main Authors: Paulsen, Frank, Bedke, Jens, Wegener, Daniel, Marzec, Jolanta, Martus, Peter, Nann, Dominik, Stenzl, Arnulf, Zips, Daniel, Müller, Arndt-Christian
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-08-2022; Springer Nature B.V
• Subjects: Approximation; Cancer therapies; Deduction; Epidemiology; Lymphatic system; Medical prognosis; Medicine; Medicine & Public Health; Metastasis; Oncology; Original; Original Article; Patients; Prostate cancer; Radiation therapy; Radiotherapy; Sensitivity; Nodal metastasis; Sensitivity; Whole-pelvis radiotherapy; Prediction model; Negative predictive value
• ISSN: 0179-7158; 1439-099X
• DOI: 10.1007/s00066-021-01841-x

Purpose
The extent of lymphadenectomy and clinical features influence the risk of occult nodes in node-negative prostate cancer. We derived a simple estimation model for the negative predictive value (npv) of histopathologically node-negative prostate cancer patients (pN0) to guide adjuvant treatment.
Methods
Approximations of sensitivities in detecting lymph node metastasis from current publications depending on the number of removed lymph nodes were used for a theoretical deduction of a simplified formulation of npv assuming a false node positivity of 0.
Results
A theoretical formula of npv = p(N0IpN0) = (100 − prevalence) / (100 − sensitivity × prevalence) was calculated (sensitivity and preoperative prevalence in %). Depending on the number of removed lymph nodes (nLN), the sensitivity of pN0-staged prostate cancer was derived for three sensitivity levels accordingly: sensitivity = f(nLN) = 9 × nLN /100 for 0 ≤ nLN ≤ 8 and f(nLN) = (nLN + 70) /100 for 9 ≤ nLN ≤ 29 and f(nLN) = 1 for nLN ≥ 30.
Conclusion
We developed a theoretical formula for estimation of the npv in pN0-staged prostate cancer patients. It is a sine qua non to use the formula in a clinically experienced context before deciding to electively irradiate pelvic lymph nodes or to intensify adjuvant systemic treatment.