Reirradiation of prostate cancer with rectum preservation: eradicative high-dose-rate brachytherapy with natural type hyaluronate injection

Abstract

Introduction: Reirradiation of locally recurrent prostate cancer after radiotherapy is limited because of its toxicity to the rectum that is closely adjacent to the prostate. To solve geometric anatomic constraints, including rectal size and distance from the prostate, we developed a technique that modifies the geometry by noninvasive direct intervention.

Methods and materials: In a patient with local recurrence of prostate cancer at 18 months after initial radiotherapy of 61.8 GyE(LQ2,3) (gray equivalent in 2 Gy/fraction at α/β=3 calculated with linear quadratic [LQ] model) to the prostate, we prescribed 16 Gy (60.8 GyE(LQ2,3) or 78.2 GyE(LQ2,1.6)) of reirradiation by high-dose-rate brachytherapy, using a bolus injection of native-type hyaluronate to create and maintain a distance between the prostate and the rectum and decrease rectal size during treatment.

Results: The procedure was achieved in 10min, without complications. Rectal D(2cc) of the reirradiation was 5.58 Gy (9.58 GyE(LQ2,3)). Compared with the initial radiation, the gel injection resulted in an improved therapeutic ratio. The patient was regularly followed up at our clinic; at over 3.5 years after reirradiation, there was no evidence of recurrence or radiation-related toxicities greater than Grade 2, maintaining a nadir prostate-specific antigen level of 0.03 ng/mL without hormonal therapy.

Conclusion: We consider that this technique is useful for achieving safe and curative reirradiation of prostate cancer.