METHODS: Medical records of breast cancer women with T2DM who received NACT from January 2016 to January 2021 at the medical center in the Gujranwala Institute of Nuclear Medicine and Radiotherapy, Pakistan, were identified and retrieved retrospectively. Variables, including pathological responses, diabetes status, and other clinical data, were collected. Patients were grouped as diabetic and nondiabetic based on the doctor's diagnosis or the diabetic's medication history recorded upon the breast cancer diagnosis. Factors influencing the pathological complete response (pCR) were determined using multivariate logistic regression utilizing IBM SPSS Statistics (version 20).

RESULTS: A total of 1372 patient files who received NACT and breast cancer surgery from January 2016 to January 2021 were selected. Out of 1372 breast cancer women receiving NACT, 345 (25.1%) had pre-existing diabetes, while 1027 (74.85%) were without pre-existing diabetes. The most common molecular subtypes of breast cancer were luminal A and B. Two hundred fifty-eight patients (18.8%) had a pCR after receiving NACT. The pCR in diabetic patients was 3.9%, and in nondiabetes, 14.9%. Most women had a pathological partial response (pPR) after the NACT 672 (48.9%). The pPR in diabetic patients was 11.0%, and in nondiabetic patients, it was 38.0%. In nondiabetics, the odds of achieving pPR increase more than pathological no response after the NACT with odd ratio: 1.71 (95% confidence interval: 1.24-2.37). The probability of pCR in patients with luminal B was 1.67 times higher than that in patients with triple-negative breast cancer with odd ratio: 1.67, 95% confidence interval (1.00-2.79), P = 0.05.