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  • br Treatment br The EBRT

    2022-05-06


    Treatment
    The EBRT was delivered to the prostate and seminal vesicles with either three-dimensional conformal radiotherapy (3DCRT) or intensity-modulated radiotherapy (IMRT) to a dose of 45 Gy in 25 fractions using 1.8 Gy fractions. Fiducial markers were inserted in 66% (n ¼ 21) of patients for image-guided radiotherapy (IGRT). In the absence of fiducial markers in situ, bony matching was used for IGRT. All patients with fidu-cial markers had IMRT. The clinical target volume (CTV) was defined as the prostate and seminal vesicles. A planning target volume (PTV) was created by adding a 7 mm margin all Selamectin around to the CTV except posteriorly where the expansion was limited to 5 mm with fiducial marker verification. In the initial cohort of patients undergoing bone matching for IGRT, the PTV was a 10 mm margin all around the CTV except posteriorly where it was limited to 7 mm. Departmental Selamectin and rectal filling protocols were followed. Dosimetry was forward planned for 3DCRT and inverse planned for IMRT on the Pinnacle v6–8 (Philips, Fitchburg, WI) treatment planning system.
    For 81% patients (n ¼ 25), LDR brachytherapy was per-formed 2–4 weeks after the completion of EBRT. The re-maining 19% of patients (n ¼ 6) underwent LDR brachytherapy before EBRT because of social reasons. In all patients, the LDR implant was performed by interstitial im-plantation using a transperineal template technique under transrectal ultrasound guidance. Volume study was acquired 2 weeks before the implant for preplanning. The brachyther-apy CTV was the prostate alone identified on the transrectal ultrasound. PTV was generated with a 3 mm expansion all around except posteriorly at the prostate/rectal wall interface, where no margin was applied. Dosimetry was forward planned adhering to TG-43 formulism in the VariSeed v8.0 (Varian, Palo Alto, CA) treatment planning system. Pre-scribed dose was 108 Gy for I125. Median seed strength was 0.43 mCi (IQR 0.413–0.433). A computed tomography scan was obtained 4 weeks post implant to assess dosimetry.
    Statistics
    The database was closed for analysis in December 2017. Biochemical failure was defined using the Phoenix consensus
    definition of the nadir PSA þ2 ng/mL. Confirmation of local recurrence or distant metastases was based on radiographic or biopsy findings. Toxicity was graded using the Common Ter-minology Criteria for Adverse Events version 4.0.
    Five-year product-limit estimates (Kaplan–Meier method) were calculated for the following prognostic factors: cT stage, ISUP grading, % biopsy core positive, risk group, and androgen deprivation therapy for different end points (bPFS/MFS/OS). The log-rank test was used to determine the magnitude of difference between the prognostic factors.
    Results
    The bPFS, local recurrence-free survival, and metastases-free survival (MFS) at 5 years were 87.1%, 95.5%, and 96.3%, respectively. The prostate cancer-specific survival and OS at 5 years were 100% and 92%, respectively. As shown in Table 2, we were unable to establish any predictors of bPFS, MFS, or OS on univariate analysis. Four patients had biochemical recurrence occurring at 24, 42, 58, and 104 months after initial presentation. Two patients had sem-inal vesicle recurrences detected on prostate-specific mem-brane antigen positron emission tomographic scans when their biochemical recurrence was confirmed (58 and 104 months). One patient had an oligometastasis detected
    Table 1
    Patient Characteristics
    Characteristics N ¼ 31 cT Stage
    Favourable 10 Unfavourable 21 ADT
    cT, clinical tumor; ISUP, International Society for Urological Pathology; ADT, androgen deprivation therapy.  Table 2
    Univariate Analysis of Clinical Factors That May Influence bPFS, MFS, and r> OS
    Clinical Prognostic Factors bPFS MFS OS
    Intermediate-Risk Group .82 .55 .44 (Favourable vs. Unfavourable)
    bPFS, biochemical progression-free survival; MFS, metastases-free sur-vival; OS, overall survival; cT, clinical tumor; ISUP, International Society for Urological Pathology; ADT, androgen deprivation therapy.
    on his prostate-specific membrane antigen positron emission tomographic scan 10 months after his biochemical recurrence (24 months) and subsequently had stereotactic body radio-therapy directed at the oligometastasis. The final patient has not developed any detectable local recurrence or metastases 73 months after his biochemical recurrence (42 months).
    The incidence of late grade 1 and 2 GU toxicities were 54.8% and 6.5%, respectively. The most common late grade 1 toxicities were urinary urgency, urinary tract pain, urinary retention, and urinary frequency. The incidence of late grade 3 GU toxicity was 6.5% with urinary retention occurring in two patients requiring either a bladder neck incision (BNI) or transurethral resection of the prostate (TURP). Of the four patients who had BNI or TURP before their treatment, one patient who had a prior BNI developed further retention with urethral stricture and required a subsequent TURP. The incidence of any late GU toxicity was 80% in the 3DCRT with bone matching IGRT cohort vs. 43% in the IMRT with fiducial marker cohort.