Treatment outcomes of simultaneous integrated boost to intraprostatic lesions with external beam radiotherapy in localized prostate cancer patients

Abstract

Background To evaluate the treatment outcomes and toxicity of definitive radiotherapy (RT) for prostate cancer (PC) patients using the simultaneous integrated boost (SIB) technique, which delivered 78 Gy to the entire prostate and 86 Gy to the intraprostatic lesion (IPL) in 39 fractions. Materials and Methods Univariable and multivariable analyses were conducted of the prognostic factors for freedom from biochemical failure (FFBF), progression‐free survival (PFS), and PC‐specific survival (PCSS) of 619 PC patients who received definitive RT between September 2012 and August 2021. Predictors of late Grade ≥2 genitourinary (GU) and gastrointestinal (GI) toxicities were also identified using logistic regression. Results The median follow‐up for entire cohort was 68.5 months. The 5‐year FFBF, PFS, and PCSS rates were 93.2%, 83.2%, and 98.6%, respectively. They were predicted by the serum prostate‐specific antigen, Gleason score (GS), clinical nodal stage, and D'Amico risk group. Only 45 patients (7.3%) developed disease recurrence 41.9 months after RT. The 5‐year FFBF rates for low‐, intermediate‐, and high‐risk disease were 98.0%, 93.1%, and 88.5%, respectively (p < 0.001). The 5‐year PFS and PCSS rates according to risk groups were 91.0%, 82.1%, and 77.4% (p < 0.001), and 99.2%, 96.4%, and 95.9% (p = 0.03), and, respectively. GS > 7 and lymph node metastasis negatively predicted FFBF and PCSS in multivariable analysis. Ninety (14.6%) and 44 (7.1%) patients had acute Grade ≥2 GU and GI toxicities, respectively, and 42 (6.8%) and 27 (4.4%) patients had late Grade ≥2 GU and GI toxicities, respectively. Diabetes and transurethral resection independently predicted late Grade 2 GU toxicity, but no significant predictor of late Grade ≥2 GI toxicity was found. Conclusions Localized PC was effectively and safely treated with definitive RT using the SIB technique to deliver 86 Gy to the IPL in 39 fractions without severe late toxicity. This finding must be validated with long‐term results.

The effect of dose‐escalation radiotherapy with simultaneous‐integrated‐boost on the use of short‐term androgen deprivation therapy in patients with intermediate risk prostate cancer

“…The recent randomized FLAME trial found that adding a focal boost to the IPL in patients with intermediate‐ and high‐risk prostate cancer improved the bDFS rate without any negative impact on toxicity or quality of life 12 . In a similar fashion, we demonstrated that localized PC was successfully and safely treated with definitive RT using the SIB technique to deliver 86 Gy to the IPL in 39 fractions without severe late toxicity 13 …”

“…All patients received 78 Gy for their prostate and the proximal portion of the seminal vesicles, while patients receiving FB received 86 Gy to IPL using the SIB technique. Until 2012, the prescribed dose to the prostate was 78 Gy, but as of 2012, the treatment protocol has been modified to include a FB to the IPL 13 . No patients received pelvic lymph node irradiation.…”

“…The planning target volume (PTV) is created by adding a 5‐mm posterior margin and 8‐mm margins in all other directions to the prostate and seminal vesicle 15,16 . The PTV for SIB was created by expanding IPL by 4 mm in all directions 13 . The treatment plans were formulated utilizing the Monte Carlo algorithm in the Monaco Treatment Planning System (Elekta Ltd.) and radiation was delivered using Versa‐HD linear accelerator (Elekta AB).…”

Evaluation of Treatment Outcomes of Prostate Cancer Patients With Lymph Node Metastasis Treated With Definitive Radiotherapy

“…The clinical target volume included the prostate and the proximal two thirds of the seminal vesicles. The planning target volume for the prostate was determined by adding a 5-mm posterior margin to the clinical target volume, with an 8-mm margin in all other directions 16,17 . The pelvic nodal area was defined according to Radiation Therapy Oncology Group guidelines, 18 except that the pelvic field extended superiorly from L4/L5 to cover the proximal common iliac lymph nodes 19 …”

Dosimetric evaluation of ultrafractionated dose escalation with simultaneous integrated boost to intraprostatic lesion using 1.5-Tesla MR-Linac in localized prostate cancer

“…Previously, we demonstrated the dosimetric feasibility of delivering 78 Gy to the entire prostate and 86 Gy to IPL using the SIB technique delivered in 39 fractions [9], and we routinely employ this technique in clinical practice [26]. Literature data suggest that 36.25 Gy is an appropriate dose to avoid urinary side effects, but it may not be sufficient to ensure proper local control, particularly for prostate cancer with a high-to-intermediate risk.…”