Mitsuo Terada1, Minoru Miyashita2, Hiraku Kumamaru3, Hiroaki Miyata3, Kenji Tamura4, Masayuki Yoshida5, Etsuyo Ogo6, Masayuki Nagahashi7, Sota Asaga8, Yasuyuki Kojima9, Takayuki Kadoya10, Kenjiro Aogi11, Naoki Niikura12, Kotaro Iijima13, Naoki Hayashi14, Makoto Kubo15, Yutaka Yamamoto16, Hiromitsu Jinno17. 1. Department of Breast Surgery, Nagoya City University Graduate School of Medical Sciences, 1, Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi, Japan. 0.032per.cent@gmail.com. 2. Department of Breast and Endocrine Surgical Oncology, Tohoku University School of Medicine, Sendai, Japan. 3. Department of Healthcare Quality Assessment, University of Tokyo, Tokyo, Japan. 4. Department of Medical Oncology, Shimane University Hospital, Shimane, Japan. 5. Department of Diagnostic Pathology, National Cancer Center Hospital, Tokyo, Japan. 6. Department of Radiology, Kurume University School of Medicine, Fukuoka, Japan. 7. Department of Breast and Endocrine Surgery, Hyogo College of Medicine, Hyogo, Japan. 8. Department of Breast Surgery, Kyorin University School of Medicine, Tokyo, Japan. 9. Division of Breast and Endocrine Surgery, Department of Surgery, St. Marianna University School of Medicine, Kawasaki, Japan. 10. Department of Surgical Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan. 11. Department of Breast Oncology, National Hospital Organization Shikoku Cancer Center, Ehime, Japan. 12. Department of Breast and Endocrine Surgery, Tokai University School of Medicine, Kanagawa, Japan. 13. Department of Breast Oncology, Juntendo University, Tokyo, Japan. 14. Department of Breast Surgical Oncology, St. Luke's International Hospital, Tokyo, Japan. 15. Department of Surgery and Oncology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan. 16. Department of Molecular-Targeting Therapy for Breast Cancer, Kumamoto University, Kumamoto, Japan. 17. Department of Surgery, Teikyo University School of Medicine, Tokyo, Japan.
Abstract
BACKGROUND: Occult breast cancer (OBC) is classified as carcinoma of an unknown primary site, and the adequate therapy for OBC remains controversial. This retrospective study aimed to reveal the transition in breast cancer therapy and the frequency of primary breast tumors after resection in clinical OBC (cT0N+) patients using the Japanese Breast Cancer Registry database. METHODS: We enrolled OBC patients with cT0N+ from the registry between 2010 and 2018. On the basis of the period of diagnosis, OBC patients were divided into the following two groups: 2010-2014 and 2015-2018. We described the transition in treatments and tumor characteristics. After breast resection, the frequency of pathological identification of primary tumors and tumor sizes was assessed. RESULTS: Of the 687,468 patients registered, we identified 148 cT0N+ patients with a median age of 61 years. Of these patients, 64.2% (n = 95) received breast surgery (2010-2014: 79.1%, 2015-2018: 50.0%). Axillary lymph node dissection was performed in 92.6% (n = 137, 2010-2014: 91.6%, 2015-2018: 93.4%). The breast tumor size in the resected breast was 0-7.0 cm (median: 0 cm, 2010-2014: 0-7.0 cm [median: 0 cm], 2015-2018: 0-6.2 cm [median: 0 cm]). The pathological identification rate of the primary tumor was 41.1% (n = 39, 2010-2014: 40.4%, 2015-2018: 42.1%). CONCLUSIONS: Breast surgery for cT0N+ decreased between 2010 and 2018. Despite the high identification rate of primary tumors, most tumors were small, and there was no significant change in the identification rate or invasive diameter of the identified tumors after 2010.
BACKGROUND: Occult breast cancer (OBC) is classified as carcinoma of an unknown primary site, and the adequate therapy for OBC remains controversial. This retrospective study aimed to reveal the transition in breast cancer therapy and the frequency of primary breast tumors after resection in clinical OBC (cT0N+) patients using the Japanese Breast Cancer Registry database. METHODS: We enrolled OBC patients with cT0N+ from the registry between 2010 and 2018. On the basis of the period of diagnosis, OBC patients were divided into the following two groups: 2010-2014 and 2015-2018. We described the transition in treatments and tumor characteristics. After breast resection, the frequency of pathological identification of primary tumors and tumor sizes was assessed. RESULTS: Of the 687,468 patients registered, we identified 148 cT0N+ patients with a median age of 61 years. Of these patients, 64.2% (n = 95) received breast surgery (2010-2014: 79.1%, 2015-2018: 50.0%). Axillary lymph node dissection was performed in 92.6% (n = 137, 2010-2014: 91.6%, 2015-2018: 93.4%). The breast tumor size in the resected breast was 0-7.0 cm (median: 0 cm, 2010-2014: 0-7.0 cm [median: 0 cm], 2015-2018: 0-6.2 cm [median: 0 cm]). The pathological identification rate of the primary tumor was 41.1% (n = 39, 2010-2014: 40.4%, 2015-2018: 42.1%). CONCLUSIONS: Breast surgery for cT0N+ decreased between 2010 and 2018. Despite the high identification rate of primary tumors, most tumors were small, and there was no significant change in the identification rate or invasive diameter of the identified tumors after 2010.