Targeted Radiotherapy Using Contact X-ray Brachytherapy 50 kV

Area of Science:

• Oncology
• Radiation Oncology
• Surgical Oncology

Background:

• Rectal adenocarcinoma is radioresistant, necessitating advanced radiotherapy for non-operative management (NOM).
• Endocavitary brachytherapy (ECB) enhances tumor dose, with Contact X-ray brachytherapy (CXB) being a precise method.
• CXB uses low-penetration 50 kV X-rays for accessible, small rectal tumors.

Purpose of the Study:

• To evaluate the efficacy of Contact X-ray brachytherapy (CXB) as a boost to chemoradiotherapy for rectal cancer.
• To assess the impact of CXB on organ preservation (OP) and clinical complete response (cCR) rates.
• To compare CXB boost with external beam radiotherapy (EBRT) boost in the OPERA Phase III trial.

Main Methods:

• Focus on Contact X-ray brachytherapy (CXB), delivering 80–110 Gy in 3–4 fractions over 3–6 weeks.
• Utilized the Papillon P50TM device for CXB, pioneered by Papillon and used in European institutions.
• The OPERA Phase III trial compared CXB boost (90 Gy/3 fr) versus EBRT boost (9 Gy/5 fr) with chemoradiotherapy for T2-T3, N0-N1 rectal tumors.

Main Results:

• Historical data shows Papillon's CXB achieved ~85% local control for tumors < 3 cm.
• The Lyon R96-2 trial demonstrated CXB boost improved cCR and sphincter preservation when combined with preoperative EBRT.
• OPERA trial interim results (2-year follow-up) showed 77% cCR and 72% OP in 141 patients; 86% cCR and 85% OP for tumors < 3 cm.

Conclusions:

• Contact X-ray brachytherapy (CXB) is a viable option for organ preservation in selected early-stage rectal cancer.
• Combining CXB boost with chemoradiotherapy shows significant potential for high rates of clinical complete response and organ preservation.
• This approach warrants consideration for well-informed patients discussed within a multidisciplinary team (MDT).