Our study introduced and validated an integrated model that accurately stratifies non-pCR breast cancer patients based on clinicopathologic features, depth, and radiomic features extracted from PET/CT images obtained before NAC administration. The integrated model secured the highest AUC values among the independent validation cohort with a 3-year survival AUC value reaching 0.889 and a 5-year survival AUC value of 0.938, respectively.
We found that the model combining radiomic, depth features and clinicopathologic factors achieved better predictive performance than individual prognostic factors. Though some studies showed that patients with an increased RCB score have a high risk of a worse prognosis and shorter survival time [9, 27], and others have indicated that combining RCB and KI67 can provide better predictions than the RCB system [10, 28], highlighting the importance of including more comprehensive and meaningful information in prediction models. In both the training set and validation set, our combined model consistently outperforms the RCB model alone in accurately predicting the prognosis of breast cancer patients, with an AUC value of 0.943 and 0.938 for 5-year survival, respectively. This underscores the added value and potential synergistic effect of integrating radiomics with traditional clinical and pathological information for more accurate prognostic predictions in breast cancer patients.
Individual metabolic factors were not a reliable predictor of survival. PET/CT allows for the simultaneous assessment of metabolic and structural functions, with research primarily focusing on PET/CT metabolic parameters such as standard uptake value (SUV) and metabolic tumor volume (MTV) in predicting the prognosis of breast cancer patients [29–33]. Nonetheless, semi-quantitative parameters obtained from PET/CT images have certain limitations in their capacity to fully capture the heterogeneity of breast cancer. For instance, while SUVmax denotes solely the hottest pixel, MTV is reliant upon methods that are based on thresholds. Our study also included metabolic indicators such as SUVmax as relevant clinical factors for prognostic analysis, but individual metabolic factors alone did not improve predictive performance. This finding supports the controversy surrounding the inconsistency between 18F-FDG tumor uptake and prognosis prediction, which might be due to tumor heterogeneity and different research methods [34, 35].
We successfully developed an integrated model based on depth and radiomic features from PET images that accurately predicted long-term survival in non-pCR breast cancer patients. Radiomics and deep learning are efficient diagnostic tools with a variety of clinical applications [36, 37]. The extraction of numerous image features from the region of interest is achieved through the utilization of mathematical algorithms in these approaches [38], and non-invasive biomarkers derived from PET radiomics can be generated based on a range of pixel intensities, associated parameters, and positions of the images. [39]. Several studies were exploring the clinical and technical viability of PET radiomics for breast cancer diagnosis [40, 41], staging [42, 43], pathological characterization [44, 45], and prediction of response to NAC [46–48]. Clément Bouron [49] investigated to evaluate the prognostic value of baseline PET/CT metabolic parameters, volumetric parameters, and texture parameters for early TNBC breast cancer. The study revealed that imaging feature entropy demonstrated potential as a prognostic indicator. David [50] discovered that texture features exhibited a significant correlation with OS and DFS in patients with advanced breast cancer. However, few studies have investigated PET/CT radiomics and depth features for prognosis prediction in non-pCR breast cancer patients. In this study, our combined model incorporating tumor stage, RCB, radiomic, and depth features exhibited excellent performance, with a five-year survival AUC of 0.943 and 0.938 in the training and validation cohorts. The combined model also demonstrated robust clinical usefulness with greater benefits in both the training and validation cohorts in DCA curve analysis.
The limitations of the present study include a single-center design and retrospective methodology. To establish the validity and generalizability of our findings, additional research is warranted. While our deep learning model performed better than the radiomics model in the training set, further investigation is necessary to elucidate the interpretability of feature sources associated with this approach.