A new study published in December 2022, authored by Noelia Sanmamed, Lisa Joseph, Juanita Crook, Tim Craig, Padraig Warde, Anne Di Tomasso, Peter Chung, Alejandro Berlin, Andrew Bayley, Elantholi P Saibishkumar, Rachel Glicksman, Srinivas Raman, Charles Catton and Joelle Helou, has compared the long-term oncologic outcomes of intermediate-risk (IR) prostate cancer patients (PCa) treated with low dose-rate brachytherapy (LDR-BT) versus those treated with moderate hypofractionated external beam radiotherapy (HF-EBRT).

Factors that are compared include the biochemical disease-free survival (bDFS) in patients treated with LDR-BT or HF-ERBT, as well as the PSA (Prostate Specific Antigen) nadir (defined as the lowest PSA achieved after the treatment) at 4 years; distant metastases; prostate cancer-specific survival (PCSS) and overall survival (OS).

Patients with intermediate-risk localised prostate cancer have several choices to make among curative-intent treatments, such as radical prostatectomy, external beam radiotherapy (EBRT) and LDR brachytherapy.

Previous studies have found that LDR-BT reports long-term bDFS, with rates over 90%. On the other hand, HF-EBRT is thought to enhance biological effectiveness, thus offering a non-invasive method of dose escalation, with a promise of more convenience.

Observational data has previously suggested a higher biochemical disease-free survival rate in patients treated with LDR-BT compared to standard fractionated EBRT. However, before this study, there was no published data comparing moderately HF-EBRT to LDR-BT – with treatment choice being based on patient preference, physician expertise and treatment availability.

The research included patients who were diagnosed with intermediate-risk prostate cancer and treated with either LDR-BT or HF-EBRT between January 2005 and December 2013. Overall, 246 patients with IR PCa were treated, 122 patients with LDR-BT and 124 with HF-EBRT. Within the study, the Kaplan-Meier (KM) method was used to estimate OS and PCSS, and a log-rank test was used to compare treatment groups. Furthermore, a 2-tailed p-value <0.05 was considered statistically significant.

The results found that patients in the HF-EBRT cohort had a higher ISUP (International Society of Urologic Pathologists) grade, with 28% and 11% of patients presenting with ISUP grade 3 in HF-EBRT and LDR-BT respectively.

Additionally, the median PSA nadir was 0.05 ng/ML for LDR-BT and 0.33ng/ML for HF-EBRT. Furthermore, the median PSA at 4 years was 0.09ng/ML and 0.52ng/ML respectively.

A biochemical recurrence was observed in 5 patients treated with LDR-BT and 34 treated with HF-EBRT. At 60 and 90 months, the cumulative index function (CIF) of BR was 0.9% and 3.5% in the LDR-BT group vs. 16.6% and 23.7% in the HF-EBRT group, respectively.

2 patients treated with LR-BT developed metastases, versus 12 treated with HF-EBRT, in which all had UIR disease. At 90 and 108 months, the CIF of metastases was 0% and 1.6% in the LDR-BT group compared to 3.4% and 9.1% in the HF-EBRT group.

4 and 22 patients were treated with salvage intent in the LDR-BT and HF-EBRT cohorts respectively. In the LDR-BT group, salvage treatment consisted of ADT (hormone therapy), lymph node dissection and high-intensity focused ultrasound, whereas in the HF-EBRT group, 16 patients received ADT, 5 were treated with BT (brachytherapy), and 1 underwent HIFU (High-Intensity Focused Ultrasound)

At the last follow-up, 24 patients were deceased in the entire cohort; 15 in the HF-EBRT group and 9 in the LDR-BT group. Prostate cancer was the leading cause of death in 3 of 10 patients in the HF-EBRT group, compared to 0 in the LDR-BT group.

In conclusion, LDR-BT was associated with higher biochemical and metastases control in the cohort when compared to moderately HF-EBRT. The research found that in the absence of a randomised trial, LDR-BT, when feasible, should be offered to younger patients with a life expectancy of >8 years.

Saheed Rashid, managing director, BXTA adds: “This study unequivocally refutes prior thinking that HF-EBRT offers enhanced biological effectiveness. On every clinical measure, LDR brachytherapy delivers improved patient outcomes over HF-EBRT and is therefore further clinical proof that LDR-B is indeed a highly viable treatment option for intermediate-risk prostate cancer patients.”

ENDS

Ref: N. Sanmamed et al. , Long-term oncologic outcomes of low dose-rate brachytherapy compared to hypofractionated external beam radiotherapy for intermediate -risk prostate cancer, Brachytherapy https:// doi.org/ 10.1016/ j.brachy.2022.09.159