From the Guidelines
The chance of achieving a complete remission (CR) with Trastuzumab (Herceptin) and other Neoadjuvant Therapies (TNT) in rectal cancer is approximately 71-76%, as reported in the most recent study from 2024 1. The use of TNT, which may include induction chemotherapy (INCT) or consolidation chemotherapy (CCRT), has been shown to significantly improve complete response rates in rectal cancer patients.
- Key factors influencing complete response rates include:
- Tumor characteristics, such as size, stage, and location
- Molecular features, particularly microsatellite instability status
- Specific TNT regimen used
- The mechanism behind complete response involves tumor cell death through DNA damage from radiation combined with the cytotoxic effects of chemotherapy, leading to complete elimination of viable tumor cells.
- Assessment of complete response typically occurs 8-12 weeks after completion of neoadjuvant therapy using clinical examination, imaging, and sometimes endoscopic evaluation.
- It is essential to note that Trastuzumab (Herceptin) is not typically used in the treatment of rectal cancer, as it is primarily used for HER2-positive breast cancer.
- The study from 2024 1 provides the most recent and highest quality evidence, with complete response rates of 71% for TNT with INCT and 76% for TNT with CCRT, making it the basis for this recommendation.
From the Research
Neoadjuvant Therapies in Rectal Cancer
- Total Neoadjuvant Therapy (TNT) has been shown to increase pathological complete response rates in rectal cancer patients, with rates ranging from 21% to 37% 2, 3.
- Studies have identified several predictors of complete response to TNT, including younger age, normal carcinoembryonic antigen levels, clinical node-negative status, smaller tumors, and wild-type p53 and SMAD4 2.
- Neoadjuvant chemoradiotherapy (CRT) has also been shown to achieve complete response rates of approximately 20% in rectal cancer patients 4.
- The use of Trastuzumab (Herceptin) in combination with other neoadjuvant therapies in rectal cancer is not well-established, and further research is needed to determine its efficacy in this setting.
Predictors of Complete Response
- N-stage, circumferential resection margin (CRM) status, average vascularity (AV), surgical procedure, and postoperative tumor size have been identified as independent predictors of complete response after TNT 3.
- Clinical, biomarker, and radiological predictors of pathological response to fluoropyrimide-based chemoradiotherapy have been studied, but the current ability to predict response is limited 4.
Treatment Outcomes
- Patients with complete response to TNT have been shown to have excellent long-term oncologic results, with some studies suggesting that surgical resection may be unnecessary in these patients 5.
- The overall response rates to TNT in rectal cancer patients have been reported to be 21% for complete response, 21% for near-complete response, 42% for partial response, and 16% for progressive disease 3.