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Comparison of plasma amino acid profile-based index and CA125 in the diagnosis of epithelial ovarian cancers and borderline malignant tumors

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We previously developed a new plasma amino acid profile-based index (API) to detect ovarian, cervical, and endometrial cancers. Here, we compared API to serum cancer antigen 125 (CA125) for distinguishing epithelial ovarian malignant tumors from benign growths.


API and CA125 were measured preoperatively in patients with ovarian tumors, which were later classified into 59 epithelial ovarian cancers, 21 epithelial borderline malignant tumors, and 97 benign tumors including 40 endometriotic cysts. The diagnostic accuracy and cutoff points of API were evaluated using receiver operating characteristic (ROC) curves.


The area under the ROC curves showed the equivalent performance of API and CA125 to discriminate between malignant/borderline malignant and benign tumors (both 0.77), and API was superior to CA125 for discrimination between malignant/borderline malignant lesions and endometriotic cysts (API, 0.75 vs. CA125, 0.59; p < 0.05). At the API cutoff level of 6.0, API and CA125 had equal positive rates of detecting cancers and borderline malignancies (API, 0.71 vs. CA125, 0.74; p = 0.84) or cancers alone (API, 0.73 vs. CA125, 0.85; p = 0.12). However, API had a significantly lower detection rate of benign endometriotic cysts (0.35; 95 % CI, 0.21–0.52) compared with that of CA125 (0.65; 95 % CI, 0.48–0.79) (p < 0.05).


API is an effective new tumor marker to detect ovarian cancers and borderline malignancies with a low false-positive rate for endometriosis. A large-scale prospective clinical study using the cutoff value of API determined in this study is warranted to validate API for practical clinical use.

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The authors thank Mae Inada and Atsuko Fukui for their skilled technical assistance; Hiroshi Miyano, Hiroo Yoshida, and Naoko Kageyama for conducting amino acid analyses; Mai Yamamoto for data management; and Mariko Takasu for her patience in coordinating this study.

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Correspondence to Etsuko Miyagi.

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Etsuko Miyagi has no conflict of interest; Yasuyo Maruyama has no conflict of interest; Tae Mogami has no conflict of interest; Reiko Numazaki has no conflict of interest; Atsuko Ikeda serves as an employee of Ajinomoto Co., Inc.; Hiroshi Yamamoto serves as an employee to Ajinomoto Co., Inc.; Fumiki Hirahara has no conflict of interest.

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E. Miyagi and Y. Maruyama contributed equally to this study.

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Miyagi, E., Maruyama, Y., Mogami, T. et al. Comparison of plasma amino acid profile-based index and CA125 in the diagnosis of epithelial ovarian cancers and borderline malignant tumors. Int J Clin Oncol 22, 118–125 (2017).

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