Intensity-modulated radiotherapy for prostate cancer with seminal vesicle involvement (T3b): A multicentric retrospective analysis

Abstract

ObjectivesNo study has reported clinical results of external-beam radiotherapy specifically for T3b prostate cancer. The possibility of escalating the dose to the involved seminal vesicles (ISV) while respecting the dose constraints in the organs at risk is thus so far not clearly demonstrated. The objective of the study was to analyze the dose distribution and the clinical outcome in a large series of patients who received IMRT for T3b prostate cancer.Materials and methodsThis retrospective analysis included all patients who received IMRT and androgen deprivation therapy for T3b prostate cancer, between 2008 and 2017, in six French institutions, with available MRI images and dosimetric data.ResultsA total of 276 T3b patients were included. The median follow-up was 26 months. The median (range) prescribed doses (Gy) to the prostate and to the ISV were 77 (70–80) and 76 (46–80), respectively. The dose constraint recommendations were exceeded in less than 12% of patients for the rectum and the bladder. The 5-year risks of biochemical and clinical recurrences and cancer-specific death were 24.8%, 21.7%, and 10.3%, respectively. The 5-year risks of local, pelvic lymph node, and metastatic recurrences were 6.4%, 11.3%, and 15%, respectively. The number of involved lymph nodes (≤ 2 or ≥ 3) on MRI was the only significant prognostic factor in clinical recurrence (HR 9.86) and death (HR 2.78). Grade ≥ 2 acute and 5-year late toxicity rates were 13.2% and 12% for digestive toxicity, and 34% and 31.5% for urinary toxicity, respectively. The dose to the pelvic lymph node and the age were predictive of late digestive toxicity.ConclusionIMRT for T3b prostate cancer allows delivery of a curative dose in the ISV, with a moderate digestive toxicity but a higher urinary toxicity. Lymph node involvement increases the risk of recurrence and death.

Radiotherapy for Clinically Localized T3b or T4 Very-High-Risk Prostate Cancer-Role of Dose Escalation Using High-Dose-Rate Brachytherapy Boost or High Dose Intensity Modulated Radiotherapy

“…A number of studies provide evidence for the efficacy of dose escalation in prostate cancer [2,[14][15][16][17][18][19][20][21]. Our results are in line with previous findings that suggest that elevated dose could improve the bDFS rate in almost all risk groups [2,[14][15][16][17][18][19][20][21].…”

“…For very high risk group, Narang et al reported 46% of 10-year bDFS including 82% of 3D-CRT and 18% of IMRT with prescribed dose 70.2 Gy (64.8–75.6 Gy) [ 13 ]. Goupy et al reported a 5-years bDFS rate of 75.2% in T3bN0 disease with 74 (70–76) Gy of IMRT (FU 26 months) in French population [ 14 ]. Ishiyama reported 5-year bDFS of 81.9% using HDR + EBRT [ 4 ].…”

“…A number of studies provide evidence for the efficacy of dose escalation in prostate cancer [ 2 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Our results are in line with previous findings that suggest that elevated dose could improve the bDFS rate in almost all risk groups [ 2 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. We thought there were three important points to improve outcome; combination of high-dose, high-precision (IMRT and image guided radiotherapy; IGRT) radiotherapy, and androgen deprivation therapy (ADT).…”

“…We thought there were three important points to improve outcome; combination of high-dose, high-precision (IMRT and image guided radiotherapy; IGRT) radiotherapy, and androgen deprivation therapy (ADT). At first, high dose radiotherapy improved outcome [ 2 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. For example, Eade et al recommended doses of > or =80 Gy for most men with prostate cancer (5y bDFS <70 Gy, 70–74.9 Gy, 75–79.9 Gy, and >80 Gy = 70%, 81%, 83%, and 89%) [ 17 ], and Pollack et al confirmed 78 Gy arm showed superior outcome than 70 Gy arm (bDFS rates for the 70 and 78 Gy arms at 6 years were 64% and 70%) [ 18 ].…”

“…Of all techniques, BT has a unique character that allows it to deliver higher doses of radiation to the target lesion without excessive irradiation of the adjacent organs, and is considered to be one of the best radiotherapy options [ 23 ]. In addition, the lowα/β ratio and consequent high sensitivity to dose fractionation of prostate adenocarcinoma could be translated to higher sensitivity to large radiation doses per fraction than for most other malignancies [ 2 , 14 ]. Therefore, we hypothesized that the use of hypo-fractionated schedules could be a good strategy to achieve better outcomes with dose escalation; this is optimally achieved with HDR [ 24 ].…”