BACKGROUND: Pathological complete response (PCR) is the surrogate marker of the outcome of a breast cancer patient. Breast cancer (BC) patients have variable responses to neoadjuvant chemotherapy (NACT). The effect of chemotherapy on mammographic density (MD) is unclear in the literature. Also, MD and PCR correlation is not extensively studied. The aim of the present study is to find MD's potential as a PCR predictor in a resource-constrained setting. METHODS: The study included all patients of BC-related surgery from January 2018 to June 2021 with follow-up till June 2023. MD was classified by the American College of Radiology (ACR) (classes A-D) based on breast composition. The chi-square test and logistic regression analysis were used to calculate p-values. RESULTS: Out of 557 patients, 554 were female with a mean age 46.8 years (premenopausal 54.5%). ACR grades of MD A, B, C, and D were 18.1% (n = 101), 56% (n = 312), 21.5% (n = 120), and 4.3% (n = 24), respectively. The odds of having PCR with MD B, C, and D were 0.51, 0.04, and 0.03, respectively, with respect to MD A. There was a significant inverse association of PCR and Ki-67 with MD on multivariate analysis. HER2 positive, TNBC, Ki 67 >
15%, and grade 3 had significantly high PCR. CONCLUSION: MD had an inverse correlation with PCR and Ki-67. Low MD, HER2 positive, TNBC, high Ki-67 subtypes, and grade 3 were good predictors for PCR.