Abstract PO4-06-03: A comparative study between RECIST 1.1 using MRI and PERCIST 1.0 using PET/CT to evaluate the response in patients of carcinoma breast receiving neoadjuvant chemotherapy

Abstract Introduction: Breast cancer is the most common cancer in women leading to the major public health problem with an estimated new cases of 2,261,419 (11.7%). Depending upon the stage at presentation, the primary modalities vary. Presently, the primary option for HER2-positive, Triple negative cancers of size more than 2cm or nodal involvement and locally advanced breast cancer is neoadjuvant chemotherapy (NACT). Accurate assessment of the tumor response and residual cancer after undergoing NACT is considered crucial for reducing the number of local recurrence cases and to predict the prognosis as patients who achieve pathological complete response (pCR) after NACT have a longer disease free period and better overall survival as compared to non-responders. In our study we have compared the two commonly used criteria i.e. RECIST 1.0 and PERCIST 1.0. Methodology: 70 patients diagnosed with breast cancer requiring neoadjuvant chemotherapy were recruited in the study conducted in the department of surgical disciplines, AIIMS Delhi from January 2021 to December 2022. Each patient underwent a contrast enhanced MRI breast and whole body FDG PET/CT at the beginning of chemotherapy and after completion of chemotherapy within a stipuated time of two to three weeks. For RECIST 1.1 criteria, response assessment was done using MRI and PERCIST used PET/CT. The response was compared with the gold standard histopathological size. Results: Concordance between the RECIST 1.1 and PERCIST 1.0 response classifications was seen in 27 (39.1%) cases, while discordance was seen in 42 (60.8%). A significant difference was observed between RECIST 1.1 and PERCIST 1.0 (k=0.1309, p 0.0001) for response classification. Tumor response was upgraded in 32 and downgraded in 2 patients using PERCIST 1.0 as compared to RECIST 1.1. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy to predict pCR along with comparison among different molecular subtypes is shown in the table below. Conclusion: RECIST 1.1 showed high specificity, PPV and accuracy in predicting pathological complete response but tends to underestimate it whereas PERCIST 1.0 showed higher sensitivity with a tendency to overestimate. RECIST 1.1 had a high level of specificity and NPV as compared to the PERCIST 1.0, which showed a high level of sensitivity and PPV. Thus, they act as complementary modalities for predicting pathological complete response. The accuracy to predict pCR was higher for the triple-negative phenotype and Her2 neu enriched with PERCIST 1.0 as compared to RECIST 1.1, while that of PERCIST 1.0 was lower for luminal type. Table. Comparison of RECIST 1.1 and PERCIST 1.0. Citation Format: Anita Dhar, Kanika Sharma. A comparative study between RECIST 1.1 using MRI and PERCIST 1.0 using PET/CT to evaluate the response in patients of carcinoma breast receiving neoadjuvant chemotherapy abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-06-03.