Triple negative breast cancer: 5-year results of combined treatment

2 National Centre of Pathology, Vilnius, Lithuania Background. Breast cancer is the most common female cancer worldwide. It is a heterogeneous disease with regard to biological behaviour, responses to treatment and prognosis. The term “triple negative breast cancer” (TNBC), namely, refers to the immunohistochemical classification of breast tumours lacking ER, PgR, and HER2 protein expression. TNBC does not respond to endocrine therapy and chemotherapy remains the main systemic therapeutic option in the adjuvant and metastatic setting of TNBC. The aim of this study was a retrospective analysis of the results of combined treatment for TNBC. Patient and methods. In our retrospective analysis, we analized 431 patients with TNBC treated with combination therapy from March 2005 until December 2009 at the Institute of Oncology, Vilnius University. 52.20% of the whole group of patients were women older than 50 years. Stage I was diagnosed in 23.9%, stage II in 49.65%, stage III in 22.74%, stage IV in 3.71% of cases. According to pathological types of the tumour ductal invasive carcinoma was diagnosed in 376 patients (87.24%) and tumour grade G3 was determined in 330 patients (76.57%). All 431 patients underwent surgical treatment, 239 patients had chemotherapy (55.45%). The disease-free survival and overall survival were estimated by the Kaplan-Meier method. The Log-rank test was used for survival comparison between the groups. P < 0.05 indicated a significant statistical difference. All statistical analyses were performed using Stata Statistical Software Version 11.0. Results. Five-year overall survival for the whole group of patients was 60.0% (95% CI 54.56–64.96); 5-year overall survival for stage I was 81.92% (95% CI 71.38–88.88); 5-year overall survival for stage II was 66.35% (95% CI 58.46–73.09); 5-year overall survival for stage III was 33.99% (95% CI 23.93–44.29), p < 0.00001; five-year disease free survival for the whole group of patients was 56.1% (95% CI 50.18–61.6). Conclusions. Five-year survival was significantly higher in earlier stages of the disease (81.9%, 66.5%, 34.0% for stages I, II and III), p < 0.00001. Different results for the TNBC patient survival can be explained by biologically distinct subtypes of TNBC.


INTRODUCTION
Breast cancer is the most common female cancer worldwide.It is a heterogeneous disease with regard to biological behaviour, responses to treatment and prognosis (1,2).In 2000, Perou et al. have de mons trated that the expression of ER and HER2 represents two major determinants of breast cancer mo lecular subgroups (1).Using unsupervised hie rar chical clustering, Sorlie et al. pioneered the estab lishment of a breast cancer classification system dis tinguishing five distinct breast cancer molecular sub groups (Luminal A, Luminal B, HER2-enriched, basal-like and a normal breast-like group) that show significant differences in incidence, survival and response to therapy.The name "luminal" deri ves from similarity in expression between these tu mors and the luminal epithelium of the breast; they tipically express luminal cytokeratins 8 and 18.The luminal subtypes are characterized by the ex pression of ER, PR, and other genes associated with ER activation (2).The HER2-enriched subtype (previously the HER2+/ER-subtype) is characterized by high expression of the HER2 and proliferation gene clusters and low expression of the luminal cluster.These tumors are typically negative for ER and PR, and positive for HER2.The basal-like sub type (BLBC), so called because of some similarity in expression of the basal epithelial cells, makes up about 15-20% of breast cancers.The BLBC subtype is more commonly negative (triple negative) for all three (ER, PR and HER2) markers as well as the increased expression of basal cytokeratins such as CK 5/6 and CK17.The terms "triple-negative breast cancer (TNBC)" and "basal-like" are not comp le tely synonymous.The term "TNBC", name ly, re fers to the immunohistochemical classification of breast tumours lacking ER, PgR, and HER2 protein ex pression, whereas the BLBC subtype is defined via the gene expression microarray analysis (3,4).How ever, the TNBC phenotype currently serves as a reliable surrogate in the clinical practice.In the absence of a specific therapeutic target, conventional chemotherapy is the mainstay of TNBC treatment according to the majority of national and inter na tional guidelines (5,6).

BACKGROUND
The aim of this study was a retrospective analysis of the results of combined treatment of TNBC.

Patients
In our retrospective analysis, we analized 431 patients with TNBC treated with combined treatment from March 2004 until December 2009 at the Institute of Oncology, Vilnius University.Patients with TNBC were identified from the database of the National Pathology Center.
Treatment decisions regarding the primary surgery and the adjuvant systemic therapy were based on standards of breast cancer treatment during tumour board.All patients had received primary surgery, surgical assessment of the axillary lymph nodes and adjuvant chemotherapy mostly containing anthracyclines (77.99%), according to current national guidelines.All tumours were characterized as estrogen receptor (ER) negative, progesterone receptor (PR) negative, and HER2 negative according to current national guidelines.
The following demografic, clinical and pathological data such as patient age, stage, laterality, menopausal status, pathological tumour size, tumour type, tumour grade, nodal status, hormonal receptor, HER-2 status were determined for all 441 cases.Cases with stage IV were revised and only 16 patients with metastases to the supraclavicular lymph nodes (in the fifth edition AJCC TNM metastases to the supraclavicular lymph nodes were classified as M1 and stage IV, in the sixth and seventh edition as N3 and stage III) were analyzed and evaluated as a separate group.After the completion of the combined treatment, pa tients were followed-up every three months for two years, every 6 months for the next two years and yearly thereafter.
52.20% of the whole group of patients (225 cases) were women older than 50 years.In this group of patients 93 (41.33%) women were older than 70 years and 27 (29.03%) of them were older than 80 years.47.80% of the whole group of patients (206 cases) were younger than 50 years.Stage I was diagnosed in 23.9%, stage II in 49.65%, stage III in 22.74%, stage IV in 3.71% of cases.The tumour size was larger than 2 cm in 284 cases (63.57%).
Demographic and clinical characteristics as well as treatment options of the study group are presented in Table 1.The average age of the patients was 57.2 ± 13.4 years (median 56, range 25-88 years).At the end of the follow-up 161 patients were dead.

Statistical methods
The vital status of the study group was assessed as of September 30, 2012, by passive follow-up, using data from the population registry.The diseasefree survival (DFS) and overall survival (OS) were estimated by the Kaplan-Meier method.DFS was calculated from the date of the start of primary therapy to the date of breast cancer recurrence, the date of death from any cause, or the date of the last follow-up.OS was calculated from the date of the start of primary therapy and death of any cause.The Logrank test was used for survival comparison between the groups.P < 0.
The one-year disease free survival for the entire study group was 83.69% (95% CI 79.71-86.96),In our univariate analysis age, stage, and tumour grade were the main prognostic factors.In the multivariate analysis, only age and stage were found to be independent prognostic factors for overall survival.value of specific morphological and biological features of these tumours and the results of treatment continue to raise a substantial degree of uncertainty and controversy.The clinical TNBC studies have been limited mostly by small sample sizes and short follow-up times.

The clinical data of the triple-negative phenotype indicate an aggressive course of this disease and poor clinical outcome of TNBC. The prognostic
The majority of our TNBC patients had relatively large tumours at presentation (T > 2 cm in 63.57% of patients), the dominant type of the tumour was invasive ductal carcinoma (87.24%), the majority of tumours were poorly differentiated (76.57%), almost half of patients had positive axillary lymph nodes at presentation (Table 1).
Simillar data were presented in some previous reports where TNBC were described as relatively large tumours (>2 cm), grade 3 and with a high rate of node positivity (7)(8)(9).In the population based Ca rolina Breast Cancer Study (CBCS), all ba sal like breast cancers (defined by triple negative sta tus plus EGFR or cytokeratin 5 positivity) were vir tually of ductal or mixed histology (90%), and of high grade (84%), which is similar to our results (10).The current theory points out to the sugges tion that TNBCs metastasize to axillary nodes and bones less frequently than the non-triple-negative subset of breast tumours, favouring a haematogenous spread.We found that 48.49% of TNBC developed metastasis to lymph nodes.In 34.2% of patientts with T1 TNBC, 46.5% of patientts with T2 TNBC and 71.9% of patientts with T3 TNBC invasion to axillary lymph nodes was confirmed.According to Albergaria et al. (2011) high percentage of axil lary lymph node invasion shows that the lymph node involvement in TNBC is as frequent as in other subtypes of breast cancer.The results from pub lished literature showed that TNBC frequently occurred in younger women (<50 years) (12).Advanced age at the time of breast cancer diagnosis has been asso ciated with a slightly increased probability of fa vourable tumour biology, with node-negative, hor mone receptor (HR)-positive, and human epider mal growth factor-2 (HER2)-negative breast can cers being found somewhat more frequently in older women.Nevertheless, a substantial proportion of older women still develop TNBC.A recent review from the United States estimated that ~15% of breast cancers in older patients were TNBC, and in a study from the Shanghai Cancer Hospital, TNBC represented 18.4% of all breast cancers in patients aged ≥70 years (14,15).Our data showed that 21.58% of the whole TNBC group were patients older than 70 years.
In terms of survival, a sharp decrease has been described in survival during the first 3 to 5 years after diagnosis, but distant relapse after this time is much less common (16,17).Our data had confirmed a rapid decrease in overall survival during the first 3 years and also had shown a rapid decrease in disease free survival curves during the first 3 years after diagnosis (Figs. 1, 2).
We found significantly higher survival for younger patients (70.3% vs. 50.0% in age groups <56 and >=56, respectively, p < 0.0001).The explanation for this finding was probably the difference in the treatment modalities.225 patients of the whole group were women older than 50 years, of them 93 were older than 70 years.Due to this fact, mastectomy was the main modality of local treatment; adjuvant chemotherapy was performed in a significantly smaller proportion, mainly by CMF schedule compared with antacyclines and taxanes to younger patients.
According to published data, different results of TNBC patient survival can be explained by bio logically distinct subtypes.These subtypes show different histopathological features and a different beha viour that is also reflected by patient survival (20).
The five-year survival was significantly higher in earlier stages of disease (81.9%, 66.5%, 34.0% for stages I, II and III), p < 0.00001.
Different results of the TNBC patient survival can be explained by biologically distinct subtypes of TNBC.
In patients older than 56 years the 5-year overall survival was 49.965% and for patients younger than >56 years it was 70.3%, p < 0.00001.