Elsevier

Radiotherapy and Oncology

Volume 117, Issue 2, November 2015, Pages 258-261
Radiotherapy and Oncology

Iodine-125 brachytherapy
Multiparametric MRI and post implant CT-based dosimetry after prostate brachytherapy with iodine seeds: The higher the dose to the dominant index lesion, the lower the PSA bounce

https://doi.org/10.1016/j.radonc.2015.08.020Get rights and content

Abstract

Purpose

To determine whether post-implant MRI-based dosimetry of the Dominant Intra-prostatic Lesion (DIL) could best predict the occurrence of PSA bounce after prostate brachytherapy.

Methods and materials

We selected 66 patients with a low risk prostate cancer treated with 125I prostate brachytherapy as monotherapy. Post-implant dosimetry based on day 30 CT-scan and multiparametric MRI co-registration was generated: planned D90, D95, V100, V150 values were calculated for each DIL. Bounce was defined as a PSA elevation ⩾0.2 ng/mL from the previous baseline value followed by a decrease to or below the prior nadir with no additional treatment.

Results

After a median follow-up of 35.5 months (range 13.2–72.5), a PSA bounce occurred in 24 (36.4%) patients. The mean planned D90 of the DIL was significantly lower in bouncers: 196 ± 61 Gy vs. 234 ± 62 Gy, p = 0.018. The mean planned V150 of the DIL was 56 ± 32% for bouncers while it was 75 ± 30% for non-bouncers, p = 0.026.

Conclusion

A lower planned D90 or V150 in the DIL were predictive of PSA bounce after prostate brachytherapy. PSA bounce could be caused by delayed cell death related to sublethal damage accumulation in the tumor.

Section snippets

Methods and materials

Sixty-six patients with a low risk prostate adenocarcinoma have been included in this retrospective analysis.

Results

Patients and treatments’ characteristics are summarized in Table 1, Table 2, according to the presence or absence of a PSA bounce. The median biochemical follow-up was 35.5 months (range, 13.2–72.5) after the PPI. There was no statistically significant difference between clinical and disease characteristics of patients who had a PSA bounce and those who did not. At time of analysis, no biochemical recurrence was observed.

Discussion

PSA bounces remain problematic and unpredictable in the case of localized prostate cancer after prostate brachytherapy. The pathogenesis of the bounce is still a matter of conjecture. Some clinical and dosimetric factors have been correlated with PSA bounces. Prostatitis, related to the insertion of radioactive iodine seeds or needles, younger age, the presence of benign prostatic hyperplasia (BPH), a large gland, a high D90 or V150 to the whole gland [9], a T2 stage over T1 (i.e. presence of a

Conflicts of interest

None.

Acknowledgements

We want to thank the Canceropole Grand Est for its support and funding and Prof. Jean Marc Cosset (Institut Curie, Paris) for his helpful comments and his wise advises.

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