(UroToday.com) The 2022 ASTRO annual meeting featured a prostate cancer session, including a presentation by Dr. Marcin Miszczyk discussing the association between dose escalation and risk of developing metastases in intermediate and high risk prostate cancer patients treated with radiotherapy. Radiotherapy dose escalation through brachytherapy or simultaneous integrated boost have been successfully introduced to clinical practice, facilitating improved local control of the tumor in intermediate and high risk prostate cancer patients, but not necessarily improved metastasis-free survival. Moreover, the improvement in clinical endpoints is often associated with increased risk of adverse effects. In this study, Dr. Miszczyk and colleagues analyzed the effect of high dose-rate (HDR) brachytherapy boost dose escalation on freedom from metastases, based on real-world data.
This analysis was based on a multi-institutional retrospective database of 1,641 consecutive intermediate (30%) or high risk (70%) prostate cancer patients treated with external beam radiotherapy (70.9%) or external beam radiotherapy, combined with single or double fraction brachytherapy boost (29.1%). The majority of the patients (95%) received anti-androgen therapy (ADT), and the biologically effective dose was calculated using α/β of 3 Gy. The analysis included the Kaplan-Meier method and Cox regression models. A multivariable model was constructed utilizing backward stepwise feature selection based on Akaike information criterion. The model presented adjusted hazard ratios in multivariable analysis, and was further used to create a nomogram. C-index was used to assess the model.
The median age was 63.8 years (IQR 62.9 – 73.5), the majority of patients (94.3%) received ADT, and the median biologically effective dose was 177.3 Gy in external beam radiotherapy and 270 Gy in the brachytherapy boost group. Metastasis occurred in 234 patients and the median freedom from metastases was not achieved, and (14.1%) over the course of follow up. The univariate analysis showed that biologically effective dose was significantly associated with freedom from metastases (HR 0.99; CI 95% 0.98-0.99; p<0.001), along with Gleason grade group, PSA density, maximum PSA, pre-treatment PSA, T and N stage according to TNM, previous transurethral resection of the prostate, and NCCN risk group. Backward stepwise feature selection allowed to create multivariable model which included biologically effective dose, prostate volume, Gleason grade group and NCCN risk groups:
This model presented c-index of 0.665 and 5-fold cross-validation-corrected c-index of 0.652. Both freedom from metastasis and OS were significantly higher in patients treated with brachytherapy boost within risk groups, except for freedom from metastasis in the favorable intermediate risk group:
After propensity score matching, the 5-year freedom from metastasis (91.5% vs 87.7%, p < 0.001) and 10-year OS (67.4% vs 60.8%, p < 0.001) remained significantly higher in patients treated with brachytherapy boost:
Dr. Miszczyk concluded this presentation discussing the association between dose escalation and risk of developing metastases in intermediate and high risk prostate cancer patients treated with radiotherapy with the following concluding messages:
- Biologically effective dose is an independent prognostic factor for developing metastases in patients treated with radiotherapy for intermediate or high risk group prostate cancer
- Real world data suggests that dose escalation through brachytherapy boost can be used to decrease the risk of developing metastases in patients with adverse features
Presented by: Marcin Miszczyk, MD, IIIrd Radiotherapy and Chemotherapy Department, Maria Sklodowska-Curie National Research Institute of Oncology, Gliwice, Poland
Co-Authors: Ł. Magrowski2, J. Ciepał2, R. Stando3, O. Masri2, I. Jabłońska2, K. Stawiski4, T. Krzysztofiak2, P. Wojcieszek2, G. Depowska2, K. Chimiak2, G. Bylica2, M. Gmerek2, P. Rajwa5,6, R. Suwiński2, J. Sadowski3, J. Rembak-Szynkiewicz2, and W. Majewski2; 1IIIrd Radiotherapy and Chemotherapy Department, Maria Sklodowska-Curie National Research Institute of Oncology, Gliwice, Poland, 2Maria Sklodowska-Curie National Research Institute of Oncology, Gliwice, Poland, 3Holycross Cancer Centre, Kielce, Poland, 4Medical University of Lodz, Lodz, Poland, 5Medical University of Silesia, Zabrze, Poland, 6Medical University of Vienna, Vienna, Austria
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2022 American Society of Radiation Oncology (ASTRO) Annual Hybrid Meeting, San Antonio, TX, Sat, Oct 22 – Wed, Oct 26, 2022.