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Introduction: The advances in immune checkpoint inhibitors (ICIs) were relatively slow in rare tumors. Therefore, we conducted a multi-center study evaluating the efficacy of ICI monotherapy and the combination of ICIs with chemotherapy (CT) in patients with advanced rare tumors., Methods: In this retrospective cohort study, we included 93 patients treated with ICIs for NCI-defined rare tumors from the 12 cancer centers in Turkey. The primary endpoints were the overall response (ORR) and disease control rate (DCR)., Results: The cohort's median age was 56, and 53.8% of the patients were male. The most frequent diagnosis was sarcoma (29%), and 81.7% of the patients were previously treated with at least one line of systemic therapy in the advanced stage. The ORR and DCR were 36.8% and 63.2%, respectively. The germ cell tumors had the lowest ORR (0%), while the Merkel cell carcinoma had the highest ORR to ICIs (57.1%). Patients treated with ICI + ICI or ICI plus chemotherapy combinations had higher ORR (55.2% vs. 27.6%, p = 0.012) and DCR (82.8% vs. 53.4%, p = 0.008). The median OS was 13.47 (95% CI: 7.79-19.15) months, and the six and 12-month survival rates were 71% and 52%. The median duration of response was 16.59 months, and the 12-month progression-free survival rate was 66% in responders. The median time-to-treatment failure was 5.06 months (95% CI: 3.42-6.71). Three patients had high-grade irAEs with ICIs (grade 3 colitis, grade 3 gastritis, and grade 3 encephalitis in one patient each)., Conclusion: We observed over 30% ORR and a 13-month median OS in patients with rare cancers treated with ICI monotherapy or ICI plus CT combinations. The response rates to ICIs or ICIs plus CT significantly varied across different tumor types. Responding patients had over 2 years of survival, highlighting a need for further trials with ICIs for patients with rare tumors., (© 2023 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.)

The aim of the study was to evaluate the real-world clinical outcomes of atezolizumab and bevacizumab (Atez/Bev) as the initial therapy for advanced hepatocellular carcinoma (HCC). We retrospectively analyzed 65 patients treated with Atez/Bev for advanced HCC from 22 institutions in Turkey between September 2020 and March 2023. Responses were evaluated by RECIST v1.1 criteria. The median progression-free survival (PFS) and overall survival (OS) were calculated using the Kaplan-Meier method. Cox regression model was employed to conduct multivariate analyses. The median age was 65 (range, 22-89) years, and 83.1% of the patients were male. A total of 1.5% achieved a complete response, 35.4% had a partial response, 36.9% had stable disease, and 26.2% had progressive disease. The disease control rate was 73.8% and associated with alpha-fetoprotein levels at diagnosis and concomitant antibiotic use. The incidence rates of any grade and grade ≥ 3 adverse events were 29.2% and 10.7%, respectively. At a median follow-up of 11.3 (3.4-33.3) months, the median PFS and OS were 5.1 (95% CI: 3-7.3) and 18.1 (95% CI: 6.2-29.9) months, respectively. In univariate analyses, ECOG-PS ≥ 1 (relative to 0), Child-Pugh class B (relative to A), neutrophil-to-lymphocyte ratio (NLR) > 2.9 (relative to ≤ 2.9), and concomitant antibiotic use significantly increased the overall risk of mortality. Multivariate analysis revealed that ECOG-PS ≥ 1 (HR: 2.69, P = .02), NLR > 2.9 (HR: 2.94, P = .017), and concomitant antibiotic use (HR: 4.18, P = .003) were independent predictors of OS. Atez/Bev is an effective and safe first-line therapy for advanced-stage HCC in a real-world setting. The survival benefit was especially promising in patients with a ECOG-PS score of 0, Child-Pugh class A, lower NLR, and patients who were not exposed to antibiotics during the treatment., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.)

Regorafenib, an oral multikinase inhibitor, has improved survival in metastatic colorectal cancer (mCRC) patients who have progressed on standard therapies. Our study aimed to evaluate prognostic factors influencing regorafenib treatment and assess the optimal dosing regimen in a real-life setting. We retrospectively analysed 263 patients with mCRC from multiple medical oncology clinics in Turkey. Treatment responses and prognostic factors for survival were evaluated using univariate and multivariate analysis. Of the patients, 120 were male, and 143 were female; 28.9% of tumors were located in the rectum. RAS mutations were present in 3.0% of tumors, while BRAF, K-RAS, and N-RAS mutations were found in 3.0%, 29.7%, and 25.9% of tumor tissues, respectively. Dose escalation was preferred in 105 (39.9%) patients. The median treatment duration was 3.0 months, with an objective response rate (ORR) of 4.9%. Grade ≥ 3 treatment-related toxicity occurred in 133 patients, leading to discontinuation, interruption, and modification rates of 50.6%, 43.7%, and 79.0%, respectively. Median progression-free survival (PFS) and overall survival (OS) were 3.0 and 8.1 months, respectively. RAS/RAF mutation (hazard ratio [HR] 1.5, 95% confidence interval [CI] 1.1-2.3; P = 0.01), pretreatment carcinoembryonic antigen (CEA) levels (HR 1.6, 95% CI 1.1-2.3; P = 0.008), and toxicity-related treatment interruption or dose adjustment (HR 1.6, 95% CI 1.1-2.4; P = 0.01) were identified as independent prognostic factors for PFS. Dose escalation had no significant effect on PFS but was associated with improved OS (P < 0.001). Independent prognostic factors for OS were the initial TNM stage (HR 1.3, 95% CI 1.0-1.9; P = 0.04) and dose interruption/adjustment (HR 0.4, 95% CI 0.2-0.9; P = 0.03). Our findings demonstrate the efficacy and safety of regorafenib. Treatment line influences the response, with dose escalation being more favorable than adjustment or interruption, thus impacting survival.

Purpose: Right-sided colon cancers (RCCs) and left-sided colon cancers (LCCs) have different embryological, epidemiological, physiological, pathological, genetic, and clinical characteristics, which result in differences in the course, prognosis, and outcome of disease. This study aimed to compare RCCs and LCCs regarding clinicopathological and survival characteristics., Methods: The present retrospective study included data of patients who were followed-up and treated for colon cancer from 2008 through 2017. Rectosigmoid, descending colon, and splenic flexure tumors were considered LCC, whereas hepatic flexure and ascending colon tumors were considered RCC. Tumors were staged according to the American Joint Committee on Cancer classification., Results: The study included 1725 patients (female, 58.7%) having colon cancer with a mean age of 64±12 years. Of the patients, 83.2% (n=1436) had LCC and 16.8% (n=289) had RCC. The rate of patients aged ≥65 years and the rate of patients with a family history of colon cancer were higher in the RCC patients. The rate of metastatic patients was 29.1% in the RCC group and 23.2% in the LCC group (p=0.087). The median follow-up period was 18 months in the RCC group and 23 months in the LCC group (p=0.011). Although the median survival time was higher in the LCC group (62 vs. 43 months), no significant difference was determined between the RCC and LCC groups in terms of survival., Conclusions: There are numerous clinicopathological differences between RCC and LCC and these differences are reflected in prognostic and survival differences among certain subgroups.

Aim of the Study: Aim of the study was to investigate the demographics of Ewing sarcoma family of tumours (ESTF) patients, treatment alternatives, clinical outcomes, and prognostic factors for survival., Material and Methods: We retrospectively reviewed 39 patients with ESFT who were admitted to our institute between September 2008 and September 2012., Results: The patients included 32 (82.1%) males and seven (17.9%) females of median age 24 (range, 18-66) years. Among the 27 patients with a primary osseous localization, 17 (43.5%) had a central axis localization. Fifteen patients (38.5%) had metastases at the time of diagnosis. Patients were followed up for a median period of 18 (range, 2-134) months. The median event-free survival (EFS) was 23 (range, 1-64) months, and the 1- and 4-year EFS were 60% and 48%, respectively. The median overall survival (OS) was 91 (range, 1-188) months, and the 1- and 4-year OS were 78% and 54%, respectively. Gender, age, primary tumor site, and local treatment modalities, either alone or in combination, did not have a significant effect on OS (p = 0.210, p = 0.617, p = 0.644, and p = 0.417, respectively). In contrast, osseous site of peripheral localization, limited stage, and metastasis to the bone significantly affected OS (p = 0.015, p < 0.001, and p = 0.042, respectively)., Conclusions: ESFTs are aggressive tumors with a high rate of relapse and metastatic potential. Patients with peripheral bone involvement and limited stage had a good prognosis. Appropriate surgical resection, radiotherapy, and aggressive chemotherapy regimens are recommended.

Background: The aim of this retrospective study was to evaluate the prognostic factors in patients operated for stage IIIC breast carcinoma who had > 10 positive axillary lymph nodes (pN3a)., Patients and Methods: The medical records of 302 operated N3a breast cancer patients without distant metastasis followed up in 2 medical oncology clinics in Ankara between January 1998 and June 2013 were evaluated retrospectively., Results: The median age was 50 (21-83) years. The median follow-up time was 43 (5-191) months. The patients were divided into 4 subgroups according to hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status. There were 151 (50.0%) patients in the HR+/HER2- group, 80 (26.5%) patients in the HR+/HER2+ group, 42 (13.9%) patients in the HR-/HER2+ group, and 29 (9.6%) patients in the triple negative (TN) group. At the time of analysis, 155 (51.3%) patients had recurrent disease and 117 (38.7%) patients had died. The median disease-free survival (DFS) and overall survival (OS) times were 46.0 and 78.0 months, respectively. Both the DFS and OS in the HR+/HER2- group were longer than in the other groups (log-rank p = 0.034 and p = 0.016, respectively). Menopausal status, progesterone receptor (PgR) status, and lymph node ratio (LNR; defined as the number of positive lymph nodes compared to the total number of removed lymph nodes) were found to be independent prognostic factors (p = 0.019, p = 0.001, and p = 0.012, respectively)., Conclusion: Menopausal status, PgR status, and LNR were independent prognostic factors in operated N3a breast cancer patients, who are underrepresented in breast cancer trials.

Purpose: In advanced stage renal cell cancer (RCC), overall survival (OS) of patients has been prolonged due to targeted therapies. To date, there are several prognostic risk models that have been developed for metastatic RCC (mRCC). The purpose of this study was to evaluate the outcomes of the sequential therapy (IFN-α, tyrosine kinase inhibitors/TKIs, m-TOR inhibitor) and prognostic factors in patients with mRCC, especially those with bone metastasis., Methods: We retrospectively examined the data of 82 patients with pathologically proven mRCC who were followed-up and treated at the Medical Oncology Clinic of the Dr A.Y Oncology Hospital between 2005 and 2013., Results: Median OS was 23 months in all patients with mRCC and 20 months in patients treated with TKIs. According to MSKCC and HENG risk classifications, median OS differed between the groups (p=0.02, p<0.001, respectively). Median OS was lower in patients with isolated bone metastasis compared to those with lung metastasis (16 vs 24 months, p=0.25). Median OS improved with increasing number of sequential therapies (p=0.08)., Conclusion: This study confirmed the correlation between MSKCC and HENG risk models and survival data. Additionally, it was shown that increase of the number of therapeutic lines in sequential therapy prolonged survival and that bone metastases were negative prognostic factors.

Introduction: We investigated the impact of modern chemotherapy regimens and bevacizumab following pulmonary metastasectomy (PM) from metastatic colorectal cancer (CRC)., Methods: A total of 122 consecutive patients who were curatively resected for pulmonary metastases of CRC in twelve oncology centers were retrospectively analysed between January 2000 and April 2012., Results: Of 122 patients, 14 did not receive any treatment following PM. The remaining 108 patients received fluoropyrimidine-based (n = 12), irinotecan-based (n = 56) and oxaliplatin-based (n = 40) chemotherapy combinations. Among these, 52 patients received bevacizumab (BEV) while 56 did not (NoBEV). Median recurrence-free survival (RFS) was 17 months and median overall survival (OS) has not been reached at a median follow-up of 25 months after PM. Three and five-year OS rates were 66% and 53%, respectively. RFS and OS were similar, irrespective of the chemotherapy regimen or BEV use. Positive pulmonary margin, KRAS mutation status, and previous liver metastasectomy were negative independent prognostic factors for RFS, while pathologically confirmed thoracic lymph node involvement was the only negative independent prognostic for OS in multivariate analysis., Conclusions: No significant RFS or OS difference was observed in respect to chemotherapy regimens with or without BEV in patients with pulmonary metastases of CRC following curative resection.

Purpose: Aging is an important risk factor for cancer. Molecular changes and defective immunity associated with aging result in increased susceptibility to many carcinogens of the gastrointestinal system (GIS). Comorbidities and changes in drug metabolism in elderly patients make the treatment of GIS cancers difficult., Methods: Between January 2009 and December 2012, a total of 790 patients diagnosed with GIS cancers were retrospectively evaluated. Among them, 357 patients aged ≥ 65 years constituted the study population in which the patient characteristics, disease location, TNM stage, ECOG PS, co-morbidities, chemotherapy regimens and overall survival (OS) were assessed., Results: The patient median age was 71 years (range 65-94). Cancer localizations were colorectal cancer (CRC), gastric cancer, and the pancreaticobiliary system (PBS) cancer in 178 (49.9%), 124 (34.7%), and 55 (15.4%) patients, respectively. A total of 260 (69%) patients underwent chemotherapy: 167 (64.3%) patients received optimal chemotherapy, and 93 (35.7%) suboptimal chemotherapy. The median OS was 47, 14, and 11 months in CRC, gastric, and PBS cancers, respectively. OS was better in the optimally-treated group than in the suboptimally-treated group among patients with all types of cancer. OS was 67 vs 19 months (p<0.001), 17 vs 8 months (p=0.004), and 12 vs 10 months (p=0.46) in CRC, gastric, and PBS cancers in the optimal and suboptimal chemotherapy groups, respectively. Multivariate analysis showed that the disease stage in all cancer types and optimal chemotherapy in the CRC group were important predictors of survival (p<0.001 and p=0.021, respectively)., Conclusion: Cancer is usually in advanced stage at the time of diagnosis in these elderly patients and screening programs might improve outcomes in this age group. Patients with GIS cancers (especially CRC and gastric cancer) should be encouraged to receive optimal chemotherapy regimens.

Background: Biliary tract cancers are rare, and surgical resection is the standard treatment at early stages. However, reports on the benefits of adjuvant treatment following surgical resection are conflicting. This study aimed to evaluate the factors affecting survival and adjuvant treatments in patients with surgically treated biliary tract cancers., Materials and Methods: Patient clinical features, adjuvant treatments, and efficacy and prognostic factor data were evaluated. Survival analyses were performed using SPSS 15.0., Results: The median overall survival was 30.7 months (95% confidence interval [CI], 18.4-42.9 months). Median survival was 19 months (95% CI, 6-33) for patients treated with fluorouracil based chemotherapy and 53 months (95% CI, 33.2-78.8) with gemcitabine based chemotherapy (p=0.033). On univariate analysis, poor prognostic factors for survival were galbladder localization, perineural invasion, hepatic invasion, a lack of adjuvant chemoradiotherapy treatment, and a lack of lymph node dissection. On multivariate analysis, perineural invasion was a poor prognostic factor (p=0.008)., Conclusions: Biliary tract cancers generally have poor prognoses. The main factors affecting survival are tumour localization, perineural invasion, hepatic invasion, adjuvant chemoradiotherapy, and lymph node dissection. Gemcitabine-based adjuvant chemotherapy is more effective than 5-fluorouracil-based chemotherapy.

Aim of the Study: We evaluated the possible effects of comorbid diseases and functional capacity on the survival of elderly female patients with breast cancer., Material and Methods: The study included 159 breast cancer patients aged 65 years or older. Functional status of the patients was evaluated using Katz's index of activities of daily living (ADL) and Lawton and Brody's Instrumental ADL (IADL) scale., Results: ADL-based evaluation revealed 121 patients (76.1%) were independent, 34 (21.4%) semi-dependent and 4 (2.5%) dependent whereas IADL-based evaluation showed 69 patients (43.4%) were independent, 67 patients (42.1%) semi-dependent and 23 patients (14.5%) dependent. Among the patients, 69 (43.4%) had one comorbid disease, 62 (39.0%) had two and 26 (16.4%) had three or more. Of the entire cohort, 60.4% received adjuvant chemotherapy. Based on ADL index, overall survival (OS) was significantly better in semi-dependent and independent patients than in dependent patients (p = 0.001). In the upfront non-metastatic patient subgroup, disease-free survival (DFS) was favourable in the independent patients according to ADL index (p = 0.001). Having more than one comorbid disease had an unfavourable effect on OS. In the multiple regression analysis of non-metastatic patients, stage, triple-negative histology and ADL index remained significant in terms of OS (p = 0.008, HR: 3.17, CI: 1.35-7.44; p = 0.027, HR: 2.78, CI: 1.172-6.91; and p = 0.006, HR: 0.29, CI: 0.12-0.70, respectively)., Conclusions: In elderly patients with breast cancer, evaluation of daily living activities and comorbid diseases are as important as staging and subclassification of breast cancer in the determination of prognosis and survival.

Purpose: The duration of anti-HER2 blockage therapy in metastatic breast cancer patients is still unclear. We aimed to evaluate the effect of the anti-HER2 blockage therapy duration and other factors on survival in HER2 positive metastatic breast carcinoma (MBC) patients., Methods: The medical records of 193 HER2 positive MBC patients, who did not have the opportunity to receive adjuvant trastuzumab therapy but had received trastuzumab in the metastatic setting were retrospectively evaluated., Results: The median age at diagnosis was 45.0 years (range 21-83). Ninety-two (47.7%) patients received palliative trastuzumab < 6 months median, whereas 101 patients received trastuzumab ≥ 6 months median. The median number of trastuzumab cycles was 8 (range 1-51). Median survival after breast cancer recurrence was 31.0 months (range 24.3-37.7). The duration of trastuzumab therapy had a significant impact on the prognosis of recurrent breast cancer (22.0 vs 49.0 months, for ≤ 6 months of treatment duration, respectively; p<0.0001). Survival after breast cancer recurrence for the patients who received lapatinib plus capecitabine vs those who did not was significantly different (59 patients, p=0.005). Moreover, there was a statistically significant relationship between prolonged lapatinib plus capecitabine combination therapy and improved survival after disease recurrence (p=0.022). In the multivariate Cox regression analysis, treatment with trastuzumab > 6 months (p=0.003) was the only independent prognostic factor for survival after breast cancer recurrence., Conclusion: The duration of anti-HER2 blockage therapies, especially with trastuzumab, seems to improve survival of HER2-positive metastatic breast cancer patients who were not previously treated with adjuvant trastuzumab, regardless of other therapies.

Background: Malignant melanoma is a cancer that demonstrates rapid progression and atypical clinically features with a poor prognosis., Aim: This study was performed to determine the clinical characteristics and treatment outcomes of patients with malignant melanoma in Turkey., Methods: The medical records of 98 patients between 2007- 2012 at our centers were retrieved from the patient registry. Overall survival (OS) was calculated using the Kaplan-Meier method., Results: In our study, with the median follow-up of all patients with cutaneous MM of 46.3 months, the median OS rate of all cases was 43.6 months and 5-year OS was 48.6%. However, five-year OS rates of patients with localized disease (stage I-II) and node involvement (stage III) were 60.3% and 39.6%, respectively. The median OS of stage IV patients was 8.7 months and 1-year OS rate was 26.2%. We showed that advanced stage, male gender, and advanced age in all patients with MM were significant prognostic factors of OS., Conclusions: Compared with the results of current studies from Western countries, we found similar findings concerning demographical features, histological variables and survival analyses for our patients with cutaneous MM in Turkey.

A determination of circulating tumor cell (CTC) effectiveness for prediction of progression-free survival (PFS) and overall survival (OS) was conducted as an adjunct to standard treatment of care in breast cancer management. Between November 2008 and March 2009, 22 metastatic and 12 early stage breast carcinoma patients, admitted to Ankara Oncology Training and Research Hospital, were included in this prospective trial. Patients' characteristics, treatment schedules and survival data were evaluated. CTC was detected twice by CellSearch method before and 9-12 weeks after the initiation of chemotherapy. A cut-off value equal or greater than 5 cells per 7.5 ml blood sample was considered positive. All patients were female. Median ages were 48.0 (range: 29-65) and 52.5 (range: 35-66) in early stage and metastatic subgroups, respectively. CTC was positive in 3 (13.6%) patients before chemotherapy and 6 (27.3%) patients during chemotherapy in the metastatic subgroup whereas positive in only one patient in the early stage subgroup before and during chemotherapy. The median follow-up was 22.0 (range: 21-23) and 19.0 (range: 5-23) months in the early stage and metastatic groups, respectively. In the metastatic group, both median PFS and OS were significantly shorter in any time CTC positive patients compared to CTC negative patients (PFS: 4.0 vs 14.0 months, Log-Rank p=0.013; and OS: 8.0 months vs. 20.5 months, Log-Rank p<0.001). OS was affected from multiple visceral metastatic sites (p=0.055) and higher grade (p=0.044) besides CTC positivity (log rank p<0.001). Radiological response of chemotherapy was also correlated with better survival (p<0.001). As a result, CTC positivity was confirmed as a prospective marker even in a small patient population, in this single center study. Measurement of CTC by CellSearch method in metastatic breast carcinoma cases may allow indications of early risk of relapse or death with even as few as two measurements during a chemotherapy program, but this finding should be confirmed with prospective trials in larger study populations.

Introduction: Breast cancer (BC) is a heterogeneous disease. Several subgroups have been identified, according to the clinical presentation and radiographic, pathological, biological, and molecular characteristics of the tumor. Intrinsic genetic heterogeneity may be responsible for these differences. To date, little is known about the clinical features and outcome of patients with primary metastatic BC (PMBC) defined as those presenting with stage IV disease., Material and Methods: Between September 2007 and May 2011, BC patients who were admitted to a clinic were assessed. Patients with PMBC were included in this retrospective analysis. The patients' demographic characteristics, treatment schedules, and survival data were recorded., Results: Of 2478 BC patients, 102 (4.1%) with PMBC were included in the analysis. The median age of the patients was 50 (26-90) years. Only four patients (3.9%) had previously undergone mammography. The median progression-free survival (PFS) and overall survival (OS) were 30 and 66 months, respectively. The PFS and OS were unaffected by age, menopausal status, ECOG, histology, or tumor grade. Both PFS and OS were affected by HR status (log rank p = 0.006, log rank p = 0.04), HER2 status (p = 0.001, p = 0.005), site of metastasis (p = 0.01, p = 0.04), radiotherapy (p = 0.04, OS p = 0.03), and bisphosphonate treatment (p = 0.02, p = 0.006). PFS was greater in the hormone therapy group (43 months, p = 0.03) while OS was greater in the patients that received chemotherapy (76 months, p = 0.01)., Conclusions: Mammography should be given greater emphasis, considering its importance in the prevention of PMBC. As a treatment option for bone and soft tissue metastatic PMBC patients, hormone therapy should be effective as a first-line treatment.

Purpose: The majority of patients with pancreatic cancer present with advanced disease. Systemic chemotherapy for patients with pancreatic cancer has limited impact on overall survival (OS). Patients eligible for chemotherapy should be selected carefully. The aim of this study was to analyse prognostic factors for OS in advanced pancreatic cancer patients treated with first-line palliative chemotherapy with gemcitabine alone or gemcitabine plus cisplatin., Methods: We retrospectively reviewed 343 locally advanced or metastatic pancreatic cancer patients who were treated with gemcitabine or gemcitabine plus cisplatin as first-line chemotherapy between December 2000 and June 2011. Fifteen potential prognostic variables were chosen for analysis. Univariate and multivariate analyses were conducted to identify prognostic factors associated with OS. Univariate and multivariate statistical methods were used to determine prognostic factors., Results: Among the 15 variables of univariate analysis, 6 were identified to have prognostic significance: stage (p<0.001), cholestasis (p=0.02), weight loss, prior pancreatectomy, serum CEA level (p<0.001) and serum CA19-9 level (p>0.001). In addition, age, chemotherapy and liver metastasis were of borderline significance (p=0.06). Multivariate analysis (Cox proportional hazard model) included the 6 significant prognostic factors of univariate analysis and showed that stage was independent prognostic factor for OS, as were weight loss, and serum CEA level., Conclusion: Stage, weight loss, and serum CEA level were identified as important prognostic factors for OS in advanced pancreatic cancer patients. These findings may also facilitate pretreatment prediction of OS and can be used for selecting patients for treatment.

Introduction and Purpose: The frequency of bilateral breast cancer is 1.4-11.0% among all breast cancers. It can present as synchronous (SC) or metachronous (MC). Data regarding clinical course of bilateral breast cancer are scarce. In this study, we therefore evaluated demographic, pathological and clinical characteristics, treatments and responses in bilateral breast cancer cases; making distinctions between metachronous-synchronous and comparing with historic one-sided data for the same parameters., Materials and Methods: One hundred fifty bilateral breast cancer cases from ten different centers between 2000 and 2011 were retrospectively scanned. Age of the cases, family history, menopausal status, pathological features, pathological stages, neoadjuvant, surgery, adjuvant and palliative chemotherapy/radiotherapy were examined in the context of the first and second occurrence and discussed with reference to the literature., Results: Metachronous and synchronous groups showed similar age, menopausal status, tumor type, HER2/neu expression; the family history tumor grade, tumor stage, ER-negativity rate, local and distant metastases rates, surgery, adjuvant chemotherapy application rates were identified as significantly different. Palliative chemotherapy response rate was greater in the metachronous group but median PFS rates did not differ between the groups., Conclusion: Although bilateral breast cancer is not frequent, MC breast cancer is different from SC breast cancer by having more advanced grade, stage, less ER expression, more frequent rates of local relapse and distant metastasis and better response to chemotherapy in case of relapse/metastasis.