The ‘war’ of logistic regression models in the diagnosis of ovarian cancer

With great interest we read the recent paper by Marret and colleagues1 on prediction of malignancy in adnexal masses using color Doppler energy (also called power Doppler). The authors cited only one preliminary study2 about comparison of transvaginal color Doppler imaging and color Doppler energy in the assessment of intra-ovarian blood flow in 67 adnexal masses but forget to cite several other studies that not only compared color Doppler energy with conventional color Doppler3, 4 but proposed a priori an approach similar to that obtained by Marret et al.1 using logistic regression. As stated in our previous publications5, 6, the location of flow (central or peripheral) is a useful secondary test after B-mode evaluation. This simplified approach should be recommended also because, as stated by Aslam et al.7, logistic regression models for the diagnosis of ovarian cancer currently are not accurate enough to be implemented into clinical practice. Besides, in the Marret study it is not clear if both in internal and in external validation, in Model 3 (gray scale, CA 125 > 25 U/mL and flow location), the authors used all parameters positive for the diagnosis of malignancy or, using a cut-off value of 10% probability, ‘at least two’ positive parameters. These are very important data for the reproducibility of the proposed method and they are not stated in the Results section of the study. In fact, in trying to apply this model to a population of 168 adnexal masses evaluated in our department before surgery in the last year we obtained completely different results (Table 1). In addition, a similar result is obtained in the same population using blood flow location as the only parameter (Table 1). From the statistical point of view, as Valentin et al.8 stated, a useful mathematical model should be created on the basis of a very large number of tumors. On the contrary, Marret et al. considered only 130 adnexal masses (prevalence of ovarian cancer 14%) and a large number of parameters, increasing the risk of ‘overfitting’ of the model. For this reason a wide range of confidence intervals was obtained thus further reducing the reproducibility of the study. The three models obtained have the same overall accuracy, thus it seems difficult to conclude, as the authors state, that power Doppler is useful in the diagnosis of ovarian cancer compared to the use of gray scale alone (Model 1). On the contrary, the use of power Doppler as a secondary test (blood flow location) has been tested in several multicenter studies4, 5 with good results. In conclusion, the model proposed by Marret et al. seems difficult to include in routine clinical practice. This ‘war’ of logistic regression models might also not be constructive because it increases the confusion over the diagnosis of malignancy and may increase the misdiagnosis of ovarian cancer, a critical problem in this era of mini-invasive surgery. S. Guerriero*, S. Ajossa*, L. Minerba , G. B. Melis*, * Department of Obstetrics and Gynecology, University of Cagliari, Ospedale San Giovanni di Dio, Via Ospedale 46, 09124 Cagliari, Italy, Department of Public Health, University of Cagliari, Cagliari, Italy

Topic: Ovarian cancer diagnosis and treatment
Subfield: Reproductive Medicine
Field: Medicine
Domain: Health Sciences