Peritumoral-to-tumoral apparent diffusion coefficient ratio as a marker of tumor microenvironment activity across...

This study aimed to evaluate the prognostic significance of tumoral apparent diffusion coefficient (tADC), peritumoral ADC (pADC), and the peritumoral-to-tumoral ADC (p/tADC) ratio in invasive breast cancers using high-resolution diffusion-weighted imaging.

A retrospective cohort of 149 patients with invasive breast cancer was analyzed. pADC, tADC, and p/tADC values were independently measured by two experienced radiologists. The associations between these parameters and histological grade, receptor status, Ki-67 index, and molecular subtypes were assessed. Interobserver agreement was evaluated using the intraclass correlation coefficient (ICC), and multivariate logistic regression was performed to identify independent predictors.

Although tADC was significantly associated only with tumor size (P < 0.050), both pADC and p/tADC were significantly associated with high histological grade, estrogen receptor/progesterone receptor negativity, human epidermal growth factor receptor 2 positivity, and high Ki-67 index (P < 0.01). The p/tADC ratio emerged as an independent predictor of high-grade tumors and Ki-67 ≥ 20%. Excellent interobserver agreement was observed for all ADC measurements (ICC > 0.90).

The p/tADC ratio reflects stromal and microenvironmental alterations associated with tumor aggressiveness and demonstrates stronger prognostic relevance than tADC alone. Incorporating the p/tADC ratio into routine magnetic resonance imaging (MRI) interpretation may improve preoperative risk stratification and support personalized treatment planning in invasive breast cancer.

The p/tADC ratio reflects stromal and microenvironmental changes associated with tumor aggressiveness and may serve as a noninvasive imaging biomarker. Its integration into preoperative MRI protocols may facilitate risk stratification and personalized treatment planning.