Evaluation of Residual Tumor After Neoadjuvant Treatment

Abstract

The primary benefit of neoadjuvant chemotherapy (NAC) is reduction of breast tumor size and conversion of positive lymph nodes into negative ones. In 70–90% of cases, clinical tumor response is evident depending on the type of chemotherapy and number of courses [1]. Several randomized clinical trials have established that both long-term overall and, moreover, disease-free survivals are similar after adjuvant and neoadjuvant chemotherapies (NAC) [1]. The reported overall and disease-free survival for patients who achieved a complete pathological response (pCR) were 75% and 85% respectively, at a median follow-up of nine years, compared to 58% and 73% for patients with residual disease [2]. Regular monitoring of tumor response during neoadjuvant therapy is very critical to evaluate the patient’s progress. When the patient’s tumor is progressing despite treatment, neoadjuvant therapy has to be discontinued, and prompt referral to surgery or preoperative radiation therapy is necessary [1]. In clinical trials of patients subjected to neoadjuvant chemotherapy, pCR ranged from 6–26% [3]. In contrast, it appears that pCR infrequently occurs with patients treated with neoadjuvant endocrine therapy [3]. The reported rates of pCR for endocrine treatment (tamoxifen and letrozole) ranges from <1.0% to 6.5% [3]. Clinical response does not seem to be a good surrogate marker for pCR, as only 22% of patients with clinical response achieved pCR [4].