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Original Article |
1 Department of Surgical Oncology, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands
2 Departments of Medical Technology Assessment, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
3 Departments of Surgery, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
4 Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, USA
Correspondence: Address correspondence and reprint requests to: Marjolein L Smidt; Department of Surgical Oncology, Canisius Wilhelmina Hospital, PO Box 9015 6500 GS, Nijmegen, The Netherlands; E-mail: marjoleinsmidt{at}yahoo.com
| ABSTRACT |
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Methods: Questionnaires, containing patient scenarios, were sent to surgical oncologists involved in breast cancer care. The surgeon was asked to predict the probability for non-SLN metastases for the first five scenarios. For the remaining scenarios, the patients actuarial likelihood, calculated by the nomogram, was supplied. The surgeon was asked whether or not (s)he would perform a cALND. The type of hospital and the surgeons experience were registered.
Results: The concordance-index amounted to 0.78, indicating moderate concurrence between the surgical predictions and nomogram results. The intersurgeon variation was important. About 25% of the surgeons was influenced by nomogram information and decided in one or more patients to abandon the cALND. Neither the type of hospital nor experience influenced predicting abilities or the clinical decision-making process.
Conclusion: Individual predictions of surgical oncologists for non-SLN metastases do not correlate well with the MSKCC nomogram. The distribution between intersurgeon predictions for one scenario is important. Therefore, the nomogram is superior to clinical estimations for predicting the likelihood for non-SLN metastases.
Key Words: Breast neoplasms Sentinel Lymph node biopsy Lymphatic metastasis and risk assessment
| INTRODUCTION |
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In approximately 40% of the breast cancer patients with SLNs containing metastatic disease, additional nodal metastases are detected in the cALND.1023 The SLN procedure already caused a decrease of the number of ALND in case of a negative SLN. A further reduction could be achieved through selection of a subset of patients with low suspicion for non-SLN metastases after a positive SLNB. Many authors determined factors that attempt to predict the presence of non-SLNs containing metastatic disease. The most frequently identified predictors are the size of the primary tumor (size in general12,16,2224 and size larger than 2 cm14,17,19,20) and SLN metastasis (size in general10,12,16,17,23 and macrometastasis13,14,1820), extranodal growth10,13,15,24 and lymphovascular invasion.10,14,2022,24 Some authors identified subsets with such a small risk for non-SLN metastases that an ALND could safely be omitted, but all concerned small studies and subset groups of patients.24 Several groups emphasize the importance of the recently closed trial of the American College of Surgeons (Z0011), in which patients with a positive SLN were randomized to ALND or no further axillary treatment. The aim of this trial was to reveal a subset of patients in which an ALND can be omitted. The trial was closed to poor patient accrual.
The MSKCC breast cancer group used the relevant predictors to develop a nomogram to help quantify a patients individual risk for non-SLN metastases (Fig. 1
). It provides a reasonably accurate predicted probability and was validated for a general population of Dutch breast cancer patients.11,22 For daily practice, however, it is essential to know how clinical predictions compare with the nomogram results and how these nomogram results influence the decisions that clinicians take. Comparisons of clinical versus computer-aided decision-making are rare in medical literature. One author examined prostate nomogram results against urologists predictions. He concluded that nomogram results could be of significant benefit in certain settings of clinical decision-making.25 Almost no literature could be found about the influence (nomogram) results have on clinical decision-making.26 To this purpose a systematic search in Pubmed under the MeSH-terms "forecasting, outcome assessment and breast neoplasms" and the heading "clinical decision-making" was performed.
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| METHODS |
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"What is the likelihood for residual disease in the axilla in a 50-year-old female with a 3 cm centrally located multifocal tumor. Tumor characteristics are invasive ductal cancer, nuclear grade II, estrogen-and progesteron-receptor-negative and no sign of lymphovascular invasion. One out of two SLNs is positive by immunohistochemical staining." All other scenarios are listed after the discussion.
In addition to the data required to use the nomogram, age, location of the tumor and progesteron-receptor status were supplied. The surgeon was asked to estimate the probability for non-SLN metastases for each of the first five scenarios. The accuracy of the surgical oncologists prediction was established by comparing the results with the nomogram findings.
For the second five similar scenarios, the patients individualized predicted probability for metastatic disease in non-SLNs, calculated by the nomogram, was supplied. To clarify the impact of the nomogram results on clinical decision-making, the surgeon was asked whether or not (s)he would perform a cALND, not taking into account the Dutch breast cancer guidelines.5,27
Clinicians completing the questionnaire provided the type of hospital they worked at: academic or cancer centre, regional teaching or local hospital. Surgical experienceexpressed in years after graduation from medical schoolof each surgeon was registered.28 To examine the influence of experience on predicting abilities, years were transposed to a number of decades.
An experienced statistician performed all statistical analyses with help of the statistical package SAS for Windows release 8.02.
| RESULTS |
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The probability predicted by the nomogram for the first five consecutive scenarios was 4, 10, 10, 32 and 43%. The median clinical guesstimate was 10, 10, 15, 30 and 30% (Fig. 2
). A concordance index was calculated to demonstrate concordance or discorcordance between the sequence of nomogram results and clinical estimates. The c-index scale varies from 0.5, which represents any toss of a coin, to 1.0, which represents perfection. The c-index in this study amounts to 0.78 indicating moderate concurrence. The variation between the predictions of the individual surgeons for each scenario was important, minimum and maximum values varied from 2.590 to 0100% (Fig. 3
). There is no significant difference between the predictions of surgical oncologists of the various types of hospitals. Experience did not make a difference in clinical predicting abilities either. Several models were used to test both relationships but no correlation could be found (P > 0.20, always).
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| DISCUSSION |
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In the second part of the questionnaire, the influence of the actuarial probability on clinical decision-making was determined. Of all surgeons, about 25% appears to be influenced by the nomogram results. This could not be attributed to the type of the hospital or the clinical experience.
The bar heights in Fig. 4
, representing the actuarial likelihood for non-SLN metastases and the percentage of surgical oncologists favoring the cALND, have a similar upward course. For the first scenario, however, the predicted clinical considered need for a completion ALND and actuarial likelihood for non-SLN metastases deviate widely. This is probably caused by the young age of this patient, 28 years, compared with the mean of 51 years of the other patients in this part of the questionnaire.
One author described several studies comparing actuarial and clinical predictions.26 Actuarial predictions always exceeded the mean accuracy of the clinicians and even the single best clinical prediction. If clinicians were provided with the calculated likelihood, improvement of predicting abilities occurred, but never matched the calculated prediction. Though none of the studied articles judged age as a predictive variable for non-SLN metastasis, the young age of the patient in scenario 1 may have been regarded by various surgical oncologists as exceptional.10,1216,1823 This resulted in a deviating median considered need to perform a cALND. Human judgment is colored by many factors. Fatigue, recent experience, changes in order of information, over-confidence in ones clinical judgement, inability to distinguish between valid and invalid variables and the weight of various variables influence clinical prediction. Further, a tendency exists to overrate information consistent with ones hypothesis and ignore contradictory information.26,29
Clinical experience influences diagnostic and therapeutic performance. A study on diagnostic skills of general practitioners in the first moment of consultation demonstrated a strong correlation between experience and diagnostic performance.30 Another study proved an inverse relationship between experience expressed as the number of years since graduation of medical school and performance of internists.31 A third author determined that time in practice as well as the type of the hospital had an influence on physician performance. A physician would perform optimally between 6 and 15 years after graduation in a large, multispecialty group.32 A recently published systemic review reported a decrease in performance with increasing experience in more than half of the examined studies.28 A possible drawback in this study could be that experience in treating a specific condition may not be necessarily correlated to the number of years after graduation. The present study, however, could not detect any relation between predicting abilities and clinical experience, nor the type of hospital, where the interviewee worked.
In conclusion, our study demonstrates that the individual predictions of surgical oncologists for non-SLN metastases do not correlate well with the MSKCC nomogram. Furthermore, the wide range of abilities of individual surgeons to predict non-SLN metastases is important and thus, the nomogram outperforms expert judgment.
The Scenarios
What is the risk for residual disease in the axilla? (1) In a 55-year-old woman with a 1.3 cm LIQ tumor: nuclear grade II, ER/PR+, not multifocal, no LVI and one of two SLNs positive by immunohistochemistry (IHC). (2) In a 34-year-old woman with a 0.6 cm UOQ tumor: nuclear grade III, ER+/PR, not multifocal, no LVI and one of one SLNs positive by IHC. (3) In a 50-year-old woman with a 3 cm central tumor: nuclear grade II, ER/PR, multifo-cal, no LVI and one of two SLNs positive by IHC. (4) In a 67-year-old woman with a 2.2 cm UOQ tumor: nuclear grade II, ER+/PR+, not multifocal, LVI and one of four SLNs positive by routine histology. (5) In a 61-year-old woman with a 0.9 cm UOQ tumor: nuclear grade II, ER+/PR+, multifocal, LVI and one of two SLNs positive by routine histology. Would you dissect the axilla?
(1) In a 28 year old woman with a 1.2 cm UIQ tumor: nuclear grade II, ER/PR, not multifocal, LVI and one of three SLNs positive by serial HE. The risk for residual disease calculated by the nomogram is 7%. (2) In a 62-year old woman with a 2.5 cm UIQ tumor: nuclear grade II, ER+/PR+, not multifocal, no LVI and one of three SLNs positive by serial HE. The risk for residual disease calculated by the nomogram is 8%. (3) In a 38-year-old woman with a 3.5 cm LOQ tumor: nuclear grade III, ER+/PR+, not multifocal, no LVI and one of three SLNs positive by serial HE. The risk for residual disease calculated by the nomogram is 14%. (4) In a 53-year-old woman with a 0.5 cm UOQ tumor: nuclear grade II, ER+/PR, not multifocal, no LVI and two of five SLNs positive by routine histology. The risk for residual disease calculated by the nomogram is 21%. (5) In a 50-year-old woman with a 1.5 cm UOQ tumor: lobular cancer, ER+/PR+, multifocal, no LVI and one of one SLNs positive by routine histology. The risk for residual disease calculated by the nomogram is 52%. These scenarios were presented at the Breast conference on 16 December 2004 at Memorial Sloan-Kettering Cancer Center, New York, USA, by Michelle Specht MD. The "no frozen section" nomogram was used. (LIQlower inner quadrant, LOQlower outer quadrant, UO-Qupper outer quadrant, UIQupper inner quadrant, ERestrogen receptor, PRprogesterone, LVIlymphovascular invasion)
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