Analysis of ipsilateral breast tumor recurrences after breast-conserving treatment based on the classification of true recurrences and new primary tumors.

BACKGROUND: Ipsilateral breast tumor recurrences (IBTR) after breast-conserving treatment include two different entities: true recurrence (TR) thought to occur when residual cancer cells grow gradually to detectable size and new primary (NP) thought to be de novo cancer independently arising in the preserved breast. The patients with ipsilateral breast tumor recurrence (IBTR) are potentially at high risk for subsequent distant metastasis, but many studies do not distinguish between these types of recurrence. The aim of this study is to clarify the biological difference between TR and NP, and to show the clinical significance of classifying IBTR into these two types of recurrence.

PATIENTS AND METHODS: A total of 172 patients with IBTR after breast-conserving therapy from the cohort of a long-term large scale study (Research of cancer treatment from the Ministry of Health, Labor and Welfare of Japan (no.13-9)) were analyzed. We classified IBTRs as TR or NP based on tumor location and pathological findings. The characteristics of the primary tumors of TR and NP were compared. Survival rates and risk factors of each type of IBTR were examined by the Kaplan-Meier method. The results of salvage surgery were also analyzed.

RESULTS: Of the 172 patients, 135 patients were classified as TR and 26 as NP. Eleven cases could not be categorized. The primary tumor of TR was characterized by a high rate of lymph node metastasis (37.8%) and short disease-free interval (mean DFI; 46.6 months) while that of NP showed a rather low lymph node positivity (8.7%) and longer DFI (62.1 months). The risk factors for TR were young age, positive surgical margin, omission of irradiation and positive lymph node metastasis. Those for NP were young age, omission of irradiation and contralateral breast cancer after the primary operation. The 5-year survival rates after IBTR were 71.0% in TR and 94.7% in NP (p=0.022). Salvage operation was performed in 136 IBTRs. Eighty-one patients underwent salvage mastectomy and 55 patients underwent repeat lumpectomy. Five-year survival rates after salvage operation were 75.7% for mastectomy and 84.2% for lumpectomy (N.S.). Twenty percent of patients who underwent repeat lumpectomy developed secondary local relapse within 5 years after salvage treatment. The risk factors for secondary local relapse were analyzed. Limited to cases of IBTR which received radiation therapy after the primary operation, NP was the only factor influencing secondary local relapse by univariate analysis.

CONCLUSIONS: TR and NP show clinically quite different features; time to occurrence, characteristics of the original tumor, prognosis and risk factor profile for IBTR were all different. Classifying IBTR as TR or NP can provide clinically significant data for the management of IBTR.