Main Session
Sep
27
PQA 01 - Gastrointestinal Cancer and Central Nervous System
2072 - Initial Experience of Modern External Beam Dose Escalation in the Setting of Total Neoadjuvant Therapy for Rectal Cancer
Presenter(s)
Gobind Gill, MD - University of Alabama at Birmingham, Birmingham, AL
G. S. Gill1, M. Evans2, K. Hardiman3, R. Hollis3, M. Akce4, G. Gupta4, M. Malla4, and N. T. Pfister1; 1Department of Radiation Oncology, The University of Alabama at Birmingham School of Medicine, Birmingham, AL, 2The University of Alabama at Birmingham Heersink School of Medicine, Birmingham, AL, 3Department of Surgery, University of Alabama at Birmingham School of Medicine, Birmingham, AL, 4Department of Medicine, University of Alabama at Birmingham School of Medicine, Birmingham, AL
Purpose/Objective(s):
Dose-escalation using brachytherapy boost has been evaluated in a phase 3 setting and demonstrated increased rates of organ preservation compared to standard of care external beam radiation therapy. However, data on dose-escalation using modern external beam radiation therapy techniques is limited. Our hypothesis is that dose-escalated external beam radiation therapy may result in increased rates of compete response when used as a component of total neoadjuvant therapy without increasing radiation-related side effects.Materials/Methods:
A single institutional retrospective review spanning 2022-2025 was performed. We searched our EMR for patients with rectal cancer treated with long course concurrent chemoradiation who received greater than 60 Gy to the primary rectal tumor. Descriptive statistics were used to quantify response rates and CTCAE side effects. Patients with prior pelvic radiation were excluded from this analysis.Results:
11 patients who received a cumulative radiation therapy dose greater than 60 Gy were identified. Two patients were excluded due to prior pelvic radiation therapy. Median follow up was 1.6 years. Median age was 64 years old. Eight (89%) patients were either T3 or T4, one (11%) patient was T2. The median radiation dose to primary rectal GTV was 64.4 Gy. All patients were treated with VMAT. Seven patients completed systemic therapy (78%). Four (44%) patients had a complete response. Six (67%) patients underwent total mesorectal excision. One (11%) patient developed local recurrence in the setting of a positive margin. With respect to radiation-related adverse events, four (44%) patients developed acute grade 2 GI events and two (22%) patients developed acute grade 3 skin reaction. Only one (11%) patient had a late grade 2 GI event.Conclusion:
In this small retrospective series, dose escalation using external beam radiation therapy provides a favorable complete response rate and did not cause any severe (grade 3+) late toxicity. Prospective trials incorporating external beam dose escalation into nonoperative management should be performed to further quantify effectiveness and safety.