CT-Based Adaptive Short Course Radiotherapy for Rectal Cancer: A Case Report.

Rectal cancer is a highly prevalent malignancy with an increasing number of treatment strategies and sequencing. Short-course radiotherapy (SCRT) combined with chemotherapy has shown to be a feasible treatment option for non-metastatic disease within the total neoadjuvant therapy paradigm. In contrast to conventionally fractionated chemoradiation, SCRT carries less logistical burden and reduces time off systemic therapy, which is particularly beneficial for patients with metastatic disease. We present a case of a 42-year-old male with metastatic rectal cancer who received SCRT using CT-based adaptive radiation, delivering 25 Gy to the pelvis with a simultaneous integrated boost of 30 Gy to the rectal tumor over five treatments. CT-based adaptive radiation was effective and well-tolerated and offers a pathway towards isotoxic radiotherapy dose escalation for patients considered to be inoperable. This case demonstrates the integration of adaptive SCRT as a promising strategy for rectal cancer.