Background Breast cancer, a leading cause of mortality among females, has been the center of research for many decades. Work is in progress to further advance the research worldwide and in our region. This study is conducted to look into regional ethical predilection, clinical presentation/stage, pathological subtypes \& risk factors of BC among patients of Karachi, with the aim of proposing a ground to policy making regarding protocol setting for screening and management of BC for our region.

Methods A prospective cohort single-centered study conducted, which included 500 female patients who attended one surgical unit of a tertiary care public hospital Karachi, during the period of 2010 - 2020. The study was performed in line with the principles of the Declaration of Helsinki and data collection started after taking hospital ethical review board's approval because personal data of patients was used. Afterwards, informed written consent was taken from every included patient. Prior to collecting data, all researchers were thoroughly trained with regards to data collection and examination of patients to eliminate observer bias. Non probability consecutive sampling technique was used. The allotted patients were followed by same researcher from presentation till the end of follow up to avoid observer bias; through direct patient interaction in OPDs and wards, radiological and histo-pathological results from investigations performed and regular follow up of patients during the complete disease period. The retrieved information was filled on pre designed pro-forma. Patients were preemptively explained about our reason for collecting data and its implications. The study is reported according to STROCSS 2021 guidelines.15 Our inclusion criteria was ; female sex, age ≥ 20 years, patients with availability of complete clinical details, biopsy proven breast cancer, no previous history of breast cancer treatment from other centers, all regional ethnicities(residents of Karachi, Sindh only) and all stages of breast cancer. Exclusion criteria of the study was; previously treated breast cancer patients, recurrent BC, female ≤19 years, male/transgender, females coming for treatment from other provinces/foreigners.

Thorough history of all patients obtained including relevant risk factors; i-e age, family history of BC, marital status, age at first born baby, parity, age of menarche/menopause, socio-economic status and ethnicity. Detailed physical examination including clinical presentation of breast lump, its size, side (right/left breast) and site, nipple discharge, nipple retraction, skin involvement, fixity to underlying structures, and lymph node status, was carried out in each patient by a single examiner. Patients presenting with a discrete lump, nipple discharge, nipple changes, skin changes, palpable axillary lymph nodes were subjected to further investigation. Ultrasonography and mammogram of the breast, where possible, were performed as initial imaging modality. FNAC/Biopsy, was carried out in all patients to confirm the diagnosis of BC, its subtype and receptors status. For staging; x-ray chest, ultrasound abdomen for liver and pelvis/ CT chest \& abdomen were done on case based need. Bone scan was performed in only symptomatic cases. After thorough overall assessment, clinical stage of BC was assigned to each patient, and stage based treatment was carried out in every patient. Patients having localized disease (≤stage 2A) underwent surgical intervention first followed by chemo/radiotherapy, regional disease(≥ stage 2B) had neo-adjuvant followed by surgery, and advanced disease(stage 4) were given palliation.16 Post operatively detailed histological report of specimen and microscopic involvement of the lymph nodes status were also noted.

Primary outcomes of the cohort were age, ethnicity, family history, stage/histological type and menopausal status while secondary outcomes were parity, marriage, symptoms, lump size/site and socioeconomic status. After collecting the required data on pro forma, it was analyzed using descriptive statistics by SPSS version 23.0 software. With sample size of 500, co-operation rate was 100% and our confidence interval was 97.5% with 5% margin of error. For quantitative data, mean and standard deviation were calculated. Qualitative results were calculated in percentages and presented in tabular forms.