Californium-252 neutron intracavity brachytherapy alone for T1N0 low-lying rectal adenocarcinoma: A definitive anal sphincter-preserving radiotherapy

Neutron brachytherapy in the modern era: Indications and evidence

Hadrontherapy is a form of radiation therapy (RT) that relies on heavy particles, such as proton, heavy ions, or neutrons, to enhance anti-tumoral efficacy based on their specific dosimetric and radio-biological properties. Neutrons are characterized by specific radiobiological properties that might deserve greater consideration, including the high linear energy transfer and the low oxygen enhancement ratio. Neutron brachytherapy, relying on interstitial or intracavitary neutron sources, has been developed since the 1950s using Californium-252 (252Cf) as a mixed emitter of fission fast neutrons and γ-photos. However, the place of NBT in the era of modern radiation therapy is yet to be precisely defined. In this systematic review, we aim to provide an up-to-date analysis of current experience and clinical evidence of NBT in the XXI ^th century, by answering the following clinical questions: How is NBT currently delivered? What are the current efficacy data and tolerance profiles of NBT?

The Evolving Strategy of Californium-252 Neutron Intracavitary Brachytherapy in Treating Patients With Low-Lying T2 or T3 Rectal Adenocarcinoma: From Fixed to Individualized Regime With Intrarectal Peritumoral Injection of Amifostine

Purpose

To retrospectively and comparatively evaluate the improvement of the efficacy and safety on the addition of ²⁵²Cf neutron intracavitary brachytherapy (ICBT), individualized or individualized with intrarectal peritumoral injection of amifostine (IPIA) to external-beam radiotherapy (EBRT) or concurrent chemo-EBRT in 314 patients with T2N0-1 or T3N0-1 low-lying rectal adenocarcinoma.

Methods

Phase I: from 2009 to 2011, 157 patients were treated with additional ²⁵²Cf neutron ICBT for four fixed fractions with a total dose of 40–45 Gy-eq during the EBRT. Phase II: from 2011 to 2013, 75 patients were treated with individualized neutron ICBT delivered for two to five fractions with a total dose of 26–45 Gy-eq according to the response of tumor after concurrent chemo-EBRT. Phase III: from 2013 to 2014, 82 patients were treated with individualized ICBT protected by pretreatment IPIA.

Results

The 4-year local control rates for the entire T2 and T3 patients were 69.4, 72.0, and 79.3%, while the 4-year overall survival rates were 63.1, 54.7, and 72.0% (P=0.08), and the 4-year disease-free survival rates were 55.4, 52.0, and 69.5% (P=0.053) in Phases I, II, and III, respectively. The late complication (LAC, ≥G2) rates were 33.8, 26.7, and 15.9%, respectively (P=0.012), and the serious LAC (≥G3) rates were 4.5, 4.2, and 0%, respectively, in Phases I, II, and III.

Conclusion

Concurrent chemo-EBRT combined with individualized ²⁵²Cf neutron ICBT protected by IPIA shows promising efficacy and safety in treating low-lying T2 and T3 rectal adenocarcinoma patients without surgery opportunity or willing.

Neutrons are forever! Historical perspectives

Purpose: Neutrons were an active field of radiobiology at the time of publication of the first issues of the International Journal of Radiation Biology in 1959. Three back-to-back papers published by Neary and his colleagues contain key elements of interest at the time. The present article aims to put these papers into context with the discovery of the neutron 27 years previously and then give a feel for how the field has progressed to the present day. It does not intend to provide a comprehensive review of this enormous field, but rather to provide selective summaries of main driving forces and developments. Conclusions: Neutron radiobiology has continued as a vigorous field of study throughout the past 84 years. Main driving forces have included concern for protection from the harmful effects of neutrons, exploitation and optimization for cancer therapy (fast beam therapy, brachytherapy and boron capture therapy), and scientific curiosity about the mechanisms of radiation action. Effort has fluctuated as the emphasis has shifted from time to time, but all three areas remain active today. Whatever the future holds for the various types of neutron therapy, the health protection aspects will remain with us permanently because of natural environmental exposure to neutrons as well as increased additional exposures from a variety of human activities.