A man in his 50s was found to have amalignant rectal tumor located 3 cm above the anal verge during a health check-up. Colonoscopy and abdominal CT scan revealed partial obstruction andpelvic lymph node, confirming the diagnosis of stage IIIB rectal adenocarcinoma. After a multidisciplinary team discussion at our hospital, we suggest total neoadjuvant therapy for him, including five fractions of short-course pelvic radiation therapy and 12 weeks of chemotherapy. Considering the patient's strong desire to maintain his quality of life and preserve the anus, we utilized MRgRT . This technology allows for daily adaptive treatment planning and real-time target monitoring, delivering precise treatment to the rectal tumor with only mild side effects. The patient was able to return to normal work within one week. Preoperative colonoscopy revealed complete tumor regression!

What are the advantages of MR-guided radiotherapy?

Reducing the radiation treatment area and minimizing side effects: Traditional treatments often encompass a slightly larger field than the actual tumor size to account for potential errors, which increases irradiating normal tissue. However, withMRgRT, the tumor image is clearer, and the radiotherapy is replanned daily. Real-time imaging monitoring during irradiation allows for a significant reduction in the radiation area, thereby minimizing damage to normal tissue. For example, in rectal cancer treatment, daily MRI corrections can sometimes detect tumor shifts of up to 2 cm. Using MRgRT enables precise targeting of the tumor without needing to extend the radiation field by 2 cm, thus reducing side effects and improving treatment success rates.

Daily Radiation Treatment Plan Adjustment: Conventional radiation therapy typically uses the same treatment plan every day, which cannot accommodate the daily anatomical and physiological changes of the patient. The ideal approach is to adjust based on the daily position and shape of the tumor and normal organs. MRgRT allows for daily adaptive planning. For example, in treating pancreatic cancer, not only does the tumor position vary daily, but the position and shape of the normal intestines also change. Only by replanning the radiation treatment daily can the most optimal results be achieved.

Providing Functional Imaging and Personalized Treatment: MRI can capture more detailed tumor information, including not only the traditional aspects of tumor location and size but also tumor activity and cellular composition. The imaging parameters obtained from daily radiation therapy can be used to predict treatment efficacy and serve as a reference for treatment adjustments. This approach ensures that each patient's treatment is no longer a fixed regimen but can be adjusted to achieve personalized cancer therapy.

Safely Increasing Radiation Therapy Dosage and Cure Rates: Conventional radiation therapy is often limited by the consideration of side effects, making it impossible to deliver an adequate dose. For example, abdominal tumors typically cannot receive sufficient radiation doses due to concerns about gastrointestinal side effects. In the case of pancreatic cancer, traditional treatment methods usually result in a tumor control rate of only 60% due to the fear of severe side effects from a full dose, which patients cannot tolerate, leading to reduced doses. With the precision treatment advantage of MR-guided radiotherapy, many clinical trials abroad have been able to increase the treatment dose without increasing side effects, thereby achieving higher cure rates.

The Tri-Service General Hospital has introduced Taiwan's first high-resolution MR-guided radiotherapy system (MRgRT 1.5T). By integrating magnetic resonance imaging (MRI) and radiation therapy technologies, this advancement offers more precise and effective treatment, leading to better treatment outcomes and quality of life for patients. With ongoing technological advancements and applications, MR-guided radiotherapy is expected to play an increasingly important role in oncological treatment, becoming a key modality in the future of cancer therapy.

Attending Physician of the Radiation Oncology Department: Wen-Yen Huang