Prognostic impact of postoperative radiotherapy in patients with breast cancer and with pT1-2 and 1-3 lymph node metastases: A retrospective cohort study based on the Japanese Breast Cancer Registry.

Postmastectomy radiotherapy (PMRT) is the standard treatment for locally advanced breast cancer. However, the effectiveness of PMRT in patients with pT1-2 and N1 tumours remains controversial. Therefore, this study aimed to determine the prognostic impact of PMRT in patients with breast cancer and with pT1-2 and 1-3 lymph node metastases. Using data from the Japanese National Clinical Database from 2004 to 2012, we evaluated the association of PMRT with locoregional recurrence (LRR), any recurrence, and mortality. We enrolled patients who had undergone mastectomy and axillary node dissection and were diagnosed with pT1-2 and N1. We compared clinicopathological factors and prognosis between patients who received (PMRT group) and those who did not receive (No-PMRT group) PMRT. Among 8914 patients enrolled, 492 patients belonged to the PMRT group and 8422 to the No-PMRT group. The median observation time was 6.3 years. There was no significant difference in the incidences of LRR (4.0% versus 5.0%, P = 0.61), recurrence (13.8% versus 11.8%, P = 0.23) and breast cancer death (6.0% versus 4.3%, P = 0.08) at 5 years between the groups. Multivariable analysis revealed that LRR was significantly associated with tumour size, number of node metastases and triple-negative subtype but not with PMRT. The LRR rate in the No-PMRT group was 5.0% at 5 years among patients with T1-2 and N1. PMRT did not significantly influence LRR in patients with T1-2 and N1. However, PMRT administration should be tailored considering the individual risks of tumour size, 3 node metastases and triple-negative subtype.

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Déclaration de conflit d'intérêts

Conflict of interest statement A.Y. received honoraria from AstraZeneca, Chugai, Daiichi Sankyo, Eisai, Eli Lily, Kyowa Kirin, Nihon Medi-physics, Nippon Kayaku, Pfizer, and Taiho. N.H. received fees from the speakers' bureaus at Chugai, Novartis, AstraZeneca, Allergan, Pfizer, Taiho, Eisai, Exact science, Eli Lily, and Daiichi Sankyo, outside the submitted work. H.K. received speaker's fees from Pfizer Japan Inc. and Johnson & Johnson KK, Chugai and consultation fees from Mitsubishi Tanabe Pharma Corporation. H.K. received speaker's fees from Pfizer Japan Inc. and Johnson & Johnson KK, and consultation fees from Mitsubishi Tanabe Pharma Corporation. H.K. and H.M. are affiliated with the Department of Health Quality Assessment at the University of Tokyo and the Social Collaboration Department supported by the National Clinical Database, Johnson & Johnson K.K., and Nipro Corporation. M.N. received honoraria from Chugai, AstraZeneca, Eli Lilly, Pfizer, Novartis, Taiho, Daiichi Sankyo, Eisai, Kyowa Kirin, and Denka. K.T. received research funds from Chugai and Eisai. K.N. received honoraria from Eisai, Nippon Kayaku, Kyowa Kirin, Novartis, AstraZeneca, Eli Lilly, Pfizer. T.I. received honoraria from AstraZeneca, Eisai, Daiichi Sankyo, Pfizer, Taiho, Eli Lilly, Nippon Kayaku and Takeda. S.O. received fees from the speakers' bureaus at AstraZeneca, Pfizer, Chugai, Eisai, Eli Lilly. S.I received Taiho, Chugai, Eisai, Daiichi Sankyo, Kyowa Kirin, Nippon Kayaku, Eli Lilly. All remaining authors have declared no conflicts of interest.