Dosimetry of local failure with single dose 19 Gy high-dose-rate brachytherapy for prostate cancer

• Published in: Radiotherapy and oncology 2021-04, Vol.157, p.93-98
• Main Authors: Armstrong, Shreya, Tsang, Yatman, Lowe, Gerry, Tharmalingam, Hannah, Alonzi, Roberto, Ostler, Peter, Hughes, Robert, Hoskin, Peter
• Format: Article
• Language: English
• Subjects: 19Gy; Brachytherapy; Dominant intraprostatic nodule; HDR brachytherapy; Humans; Local recurrence; Male; Neoplasm Recurrence, Local - radiotherapy; Prostate cancer; Prostatic Neoplasms - radiotherapy; Radiotherapy Dosage; Retrospective Studies; Single fraction
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2021.01.006

•Of 180 patients who received 19 Gy high-dose-rate brachytherapy (HDR-BT) for localised prostate cancer, with a median follow up of 36 months, 19 (10.6%) patients developed biochemical recurrence of which 13 had a local relapse, including 7 at the site of dominant intraprostatic nodule (DIL).•The 19 biochemical recurrences (failures) were matched to 19 control patients, who were matched to pre-treatment CTV size, Gleason score, T stage, risk category and presence of a DIL. For these patients, clinical and dosimetric parameters were analysed to see if there were any predictors for biochemical recurrence, local recurrence or recurrence within the DIL.•There were no statistically significant differences in all OARs, CTV, PTV and DIL dosimetric parameters between the failures and controls.•In univariate analysis, there were no statistically significant clinical or dosimetric parameters that predicted for biochemical progression free survival, local recurrence free survival or DIL recurrence free survival.•Whilst a large proportion of patients recur at the site of original disease, and these results may support rationale for further dose escalation, in our cohort actual dose delivered to DIL was around 26 Gy. Other studies employing dose escalation to whole gland or focal boost have failed to show improved clinical outcomes to justify this approach, hence HDR-BT should be undertaken using a minimum of two fractions. Long-term follow up of single dose high-dose rate brachytherapy (HDR BT) for localised prostate cancer has revealed higher than expected rates of biochemical and local failure. This study aimed (i) to investigate the pattern of relapse within the prostate with reference to the initial site of disease in those patients; and (ii) to examine if there were any relationships between the HDR BT dosimetric parameters to these areas of recurrence. A retrospective review of treatment records of patients who received 19 Gy single fraction of HDR BT was carried out. A matched pair analysis used one control for each biochemical recurrence case matched with pre-treatment Clinical target volume (CTV) size, Gleason score, T stage, risk category and presence of an identifiable dominant intraprostatic nodule (DIL) for each biochemical recurrence case identified. For all datasets, the pre HDR BT DILs were delineated on the diagnostic pre-treatment T2-weighted MRI and planning CT images. For patients with local recurrence post HDR BT, the recurrent nodules were contou