Ipsilateral in-breast tumor recurrence after breast conserving therapy: true recurrence versus new primary tumor.

Purpose: To classify ipsilateral in-breast cancer recurrences (IBCR) in patients treated with conservative surgery and radiation therapy, either as new primary tumor (NP) or true recurrence (TR) and to assess the prognostic and therapeutic importance of this classification.

Methods: The records of 107 patients treated for local tu- mor recurrence after breast-conserving therapy (BCT) at the National Cancer Center, Sofia, between March 1999 and May 2011 were retrospectively analysed. The patients'primary tumors were up to 2 cm in size. For their primary tumors all patients underwent quadrantectomy, axillary lymph node dissection and postoperative radiotherapy (RT) up to 50 Gy. In cases with nodal metastasis additional RT has been used. Adjuvant chemotherapy and hormonotherapy have been used according to the clinical indications and depending of the patient's condition. Every attempt was made to define a tumor as a TR or NP, based on the changes in location and histology. (99m)Tc-MIBI SPECT-CT was used to localize the site of recurrence.

Results: Forty-four (41.1%) of the relapses were TR and 63 (58.9%) NPs. Out of 63 relapses defined as NPs, 54 (85.7%) changed the location and 49 (68.3%) had a different histology. The age of patients with TR and with NP did not differ significantly at the time of diagnosis of the primary tumor (TR 48.8±10.45 years vs NP 50.8±10.56; p<0.330), but those who developed TR were significantly younger than those with NP at the time of recurrence (TR 53 years, 66±11.1 vs NP 58.15+10.6; p<0.05). Recurrences defined as NPs, developed after a significantly longer period of time in comparison to the TRs (7.4±2.6 years vs 4.8±2.2 years; p<0.0001). Five-year overall survival of patients with TR was significantly lower compared to patients with NP (31.8% vs 96.7% p=0.0001).

Conclusions: Recurrences developing after BCT represent different clinical events, having different origin, prognosis and, therefore, requiring different type of treatment. It seems that a significant part of the recurrences that develop in the residual parenchyma, following BCT, are new carcinomas.