Comparison of Breast cancer outcomes in patients with and without Type 2 Diabetes: A Retrospective cohort study

INTRODUCTION

Breast cancer is the most commonly diagnosed cancer worldwide, with 2.3 million new cases annually. In India, it accounts for about 13.5% of all cancer cases, with survival rates sharply decreasing as the disease progresses. Poor outcomes in India are linked to late diagnosis, younger age at onset, delayed treatment, and inadequate care.

Type 2 Diabetes, affecting over 77 million people in India, shares common risk factors with breast cancer, such as obesity and aging. Diabetes may lead to more aggressive breast cancer due to elevated insulin and blood sugar levels, which activate tumour-promoting pathways (PI3K/Akt/mTOR). Chronic inflammation, hormonal imbalances, and metabolic disruptions further connect the two diseases.

OBJECTIVES OF THE STUDY

To compare the breast cancer outcomes such as survival, rehospitalization, recurrence, metastasis among Type 2 Diabetes and non-Type 2 Diabetes patients.

To assess the effects of breast cancer treatment on changes in HbA1c levels and anti-diabetic medication therapy among the breast cancer patients with Type 2 Diabetes.

To assess the various factors that influence the breast cancer outcomes.

JUSTIFICATION FOR THE STUDY

This study is crucial for evaluating patient outcomes by assessing the factors associated with DM and breast cancer and finding a potential link between the two. Comparing outcomes between these groups is important as T2DM may worsen prognosis through metabolic disturbances, chronic inflammation, and treatment limitations. Evaluating the association between clinicopathological features such as tumour characteristics and hormone receptor status with patient outcomes will guide treatment decisions. Assessing how breast cancer treatment affects glycemic control and the need for changes in antidiabetic medication is essential, as therapies like chemotherapy and corticosteroids can disrupt glucose regulation. Ultimately, this research seeks to improve patient outcomes and elevate the overall understanding of importance of glycemic control in such patients.

METHODOLOGY

A retrospective cohort study will be conducted for six months, from September 2025 to February 2026. The data of the inpatients diagnosed with breast cancer will be collected from MRD for the time period, January 2014 to December 2023. A properly designed data collection form will be used to gather patient information. The patients are enrolled based on the inclusion criteria. Breast cancer patients will be categorized into two groups, patients diagnosed with Type 2 Diabetes; patients not diagnosed with Type 2 Diabetes. The factors associated with breast cancer and Type 2 Diabetes will be determined.

STATISTICAL ANALYSIS

Quantitative data will be expressed as mean ± SD or median (IQR). Qualitative data will be expressed as frequency and percentage. Chi-square test or Fisher’s exact test will be used to find association between categorical variables. Kaplan-Meier plots will be used to compare the events occurring in two groups. Cox proportional hazard models will be constructed to find the factors associating the events occurring in the groups. SPSS software version 29 will be used for statistical analysis. p<0.05 will be considered statistically significant.

OUTCOME MEASURES

Breast Cancer Outcomes

|Survival

|Recurrence and Time to Recurrence

|Rehospitalization for other complications

|Metastasis and Time to Metastasis

Factors influencing Breast cancer outcomes

|Demographic characteristics: Age

|Comorbidities

|Hormone receptor status (ER, PR, HER2)

|Tumour stage, grade, size, position

|Menopausal status

|Lymph node status

|Breast cancer treatment