Linda Bryant

High dose rate afterloading brachytherapy for prostate cancer: catheter and gland movement between fractions

Fractionated high dose rate afterloading brachytherapy for prostate cancer requires a robust means of catheter fixation with good quality assurance. Catheter position and dosimetry has been formally evaluated in 20 consecutive patients representing a total of 332 catheters undergoing two HDR afterloading brachytherapy fractions over 36 h. The mean interfraction movement of catheters as measured by external length was less than 1 mm, but within the prostate on consecutive CT scans there was a mean interfraction movement of 11.5 mm away from the prostate base. This has a significant impact on implant dosimetry as measured by D90 and the COIN index, unless corrected by repositioning the catheters.

Justification for inter-fraction correction of catheter movement in fractionated high dose-rate brachytherapy treatment of prostate cancer

BACKGROUND AND PURPOSEnFractionated high dose-rate (HDR) brachytherapy in the treatment of prostate cancer relies on reproducible catheter positions for each fraction to ensure adequate tumour coverage while minimising dose to normal tissues. Peri-prostatic oedema may cause caudal displacement of the catheters relative to the prostate gland between fractions. This can be corrected for by changing source dwell positions or by physical re-advancement of catheters before treatment.nnnMATERIALS AND METHODSnData for 20 consecutive monotherapy patients receiving three HDR fractions of 10.5 Gy per fraction over 2 days were analysed retrospectively. Pre-treatment CT scans were used to assess the effect of catheter movement between fractions on implant quality, with and without movement correction. Implant quality was evaluated using dosimetric parameters.nnnRESULTSnCompared to the first fraction (f1) the mean inter-fraction caudal movement relative to the prostate base was 7.9 mm (f2) (range 0-21 mm) and 3.9 mm (f3) (range 0-25.5 mm). PTV D90% was reduced without movement correction by a mean of 27.8% (f2) and 32.3% (f3), compared with 5.3% and 5.1%, respectively, with catheter movement correction. Dose to 2 cc of the rectum increased by a mean of 0.69 (f2) and 0.76 Gy (f3) compared with an increase of 0.03 and 0.04 Gy, respectively, with correction. The urethra V12 also increased by a mean of 0.36 (f2) and 0.39 Gy (f3) compared with 0.06 and 0.16 Gy, respectively, with correction.nnnCONCLUSIONSnInter-fraction correction for catheter movement using pre-treatment imaging is critical to maintain the quality of an implant. Without movement correction there is significant risk of tumour under-dosage and normal tissue over-dosage. The findings of this study justify additional imaging between fractions in order to carry out correction.

Critical structure movement in cervix brachytherapy

BACKGROUND AND PURPOSEnTo investigate critical structure movement and subsequent dose received during conformal MR-guided cervix brachytherapy.nnnMATERIALS AND METHODSn21 patients (36 HDR fractions) undergoing brachytherapy for cervical cancer underwent a second MR immediately prior to treatment (pre-treatment MR). Bowel (including sigmoid), bladder and rectum were outlined on both planning and pre-treatment MR scans and dosimetry compared.nnnRESULTSnNo statistically significant differences were found between the volumes of the OAR doses across the two scans but there were large variations between patients with differences of up to 3.3 Gy observed. The percentage of fractions for which D2cc was within 10% of that planned was 61.1%, 41.7% and 47.2% for bladder, rectum and bowel, respectively. The average time between MR scans was found to be 4.75 h (SD±1.2; range 3.2-9.9 h), with no correlation found with critical structure movement within this range.nnnCONCLUSIONSnOAR movement is difficult to predict though significant changes occur in individual patients. In 61% of cases in our sample the D2cc dose changed by at least 10% for at least one OAR from that planned. Pre-treatment imaging with subsequent adjustment of dosimetry will minimise the impact of organ movement on delivered dose.

Image-guided vulvovaginal interstitial brachytherapy in the treatment of primary and recurrent gynecological malignancies

PURPOSEnEvaluation of interstitial high-dose-rate brachytherapy (HDRB) to the vulvovaginal region both alone and in combination with external beam radiotherapy (EBRT) for primary or recurrent gynecological malignancy.nnnMETHODS AND MATERIALSnFrom 1998 to 2009, 37 women with a mean age of 68 years were treated with transperineal interstitial HDRB. Fifteen patients (40.5%) were treated for primary disease, whereas 22 (59.5%) patients were treated for recurrent disease. Median time to local recurrence was 31 months (2-312 months). Primary sites included endometrium (12), vulva (11), vagina (10), vulvovagina (1), cervix (1), and bladder (2). Thirty-one patients (83.7%) in this series were treated with radical intent, whereas 6 (16.3%) were treated with palliative intent. Radically treated patients received between 45 and 60Gy (median, 45Gy) of EBRT. The median number of days from EBRT to HDR boost was 5 days (1-35 days). The HDRB doses ranged from 11Gy in two fractions to 42Gy in six fractions (dose per fraction varied from 4 to 8.5Gy) and fractions were given at least 6-8h apart.nnnRESULTSnEight of the 31 patients (26%) treated with radical intent relapsed locally. Eleven of 37xa0patients (30%) treated with either radical or palliative intent recurred locally. The 2- and 5-year local progression-free survival was 74% and 63.4%, respectively. The total progression-free survival, which includes local, locoregional/nodal, and distant recurrence, at 2 and 5 years, was 73.6% and 45.6%, respectively. With a mean follow-up of 27 months (3.8-111.9 months), the median survival for the patient group was 16.6 months with a 2- and 5-year overall survival of 47.7% and 36.4%, respectively. Acute Grade 3 toxicity was seen in 13 (35%) of the 37 patients (skin: 10, urinary: 2, genital: 2, gastrointestinal: 0). No acute Grade 4 toxicities were seen. A total of 10 of the 37 patients (27%) developed late Grade 3 toxicities. Five of the 22 patients (22%) treated for recurrent disease with radical intent developed Grade 3 toxicity (skin: 4, urinary: 2, genital: 1, radiation-induced fracture of acetabulum: 1, and gastrointestinal: 0), whereas 1 of the 6 patients treated with palliative intent had Grade 3 toxicity affecting skin. No late Grade 4 toxicities were seen.nnnCONCLUSIONnThis retrospective series suggests that interstitial perineal HDRB is a safe and effective treatment option for primary or locally recurrent gynecological malignancies. It is axa0valuable option in patients who have received previous EBRT to the pelvis, achieving good local control with acceptable late treatment-related side effects.

High-dose-rate afterloading intraluminal brachytherapy for advanced inoperable rectal carcinoma

PURPOSEnHigh-dose-rate (HDR) intraluminal brachytherapy for advanced or inoperable tumors of the rectum has been used both palliatively and to dose escalate after chemoradiation for curative treatment.nnnMETHODSnBetween 1993 and 2007, 79 patients were treated with HDR afterloading brachytherapy for rectal cancer; 70 patients had adenocarcinoma of the rectum; and 9 patients had squamous cell carcinoma of the anal canal. Fifty-two patients had localized disease but were unfit for major surgery and received radiotherapy with radical intent. Twenty-seven patients with advanced or metastatic disease received palliative treatment. The median age was 82 years (range, 33-97). Radical treatment comprised either chemoradiation followed by intraluminal brachytherapy delivering 12 Gy at 1 cm in two fractions or radical monotherapy delivering up to 36 Gy at 1 cm in six fractions two to three times weekly. Palliative HDR brachytherapy schedules were predominantly 10 Gy at 1 cm single dose.nnnRESULTSnObjective local tumor response was seen in 41 of 48 assessable patients (85%); of whom, 28 patients (58%) had a complete response and 13 (27%) had a partial response. The most common symptom was rectal bleeding, which was controlled with a complete response rate of 63%. The median duration of the symptom response was 3 months (range, 1-73), and the median survival of the palliative patients was 6 months (range, 1 week-37 months). The median survival for patients treated with radical intent was 18.5 months (range, 2-119). Six patients reported late toxicity with three cases of rectal ulcer, two strictures, and one fistula.nnnCONCLUSIONSnIntraluminal HDR brachytherapy is effective as local treatment in both the radical and palliative setting, with high tumor and symptom response rates, and acceptable late toxicity.

The Influence of Prostate Volume on Outcome After High-Dose-Rate Brachytherapy Alone for Localized Prostate Cancer

OBJECTIVEnTo determine whether late genitourinary toxicity, biochemical control of prostate cancer, and dosimetric parameters in patients with large prostate glands is different from those variables in men with smaller glands after treatment with high-dose-rate brachytherapy alone (HDR-BT).nnnMETHODSnFrom November 2003 to July 2009, 164 patients with locally advanced prostate carcinoma were sequentially enrolled and treated with 34 or 36 Gy in 4 fractions and 31.5 Gy in 3 fractions of (192)Ir HDR-BT alone. The median follow-up time was 71 months. Gland size was not considered in the selection criteria for this study. Estimates of freedom from biochemical relapse (FFbR) and late morbidity, stratified by median clinical target volume (CTV), were obtained, and differences were compared.nnnRESULTSnThe median CTV volume was 60 cc (range, 15-208 cc). Dose-volume parameters D90 and V100 (ie, minimum dose to 90% of the prostate volume and volume receiving 100% of the prescribed isodose) achieved in patients with glands ≥60 cc were not significantly different from those with glands <60 cc (P≥.2). Nonetheless, biochemical control in patients with larger CTV was significantly higher (91% vs 78% at 6 years; P=.004). In univariate and multivariate analysis, CTV was a significant predictor for risk of biochemical relapse. This was not at the expense of an increase in either moderate (P=.6) or severe (P=.3) late genitourinary toxicity. The use of hormonal therapy was 17% lower in the large gland group (P=.01).nnnCONCLUSIONSnProstate gland size does not affect dosimetric parameters in HDR-BT assessed by D90 and V100. In patients with larger glands, a significantly higher biochemical control of disease was observed, with no difference in late toxicity. This improvement cannot be attributed to differences in dosimetry. Gland size should not be considered in the selection of patients for HDR-BT.

I-125 seed planning: An alternative method of urethra definition

BACKGROUND AND PURPOSEnTo investigate the use of aerated aqueous gel rather than a catheter to define the urethra during permanent I-125 seed implant planning.nnnMATERIALS AND METHODSnTwenty patients were treated between September 2007 and March 2008, each having two sequential volume studies: one visualizing the urethra with a catheter and the other using aerated gel. Two individually optimised plans were produced for each patient: one from the gel and the other from the catheter image set, and the plans were analysed dosimetrically. The plans were also interchanged (putting gel plan onto catheter image set and vice versa), and dose homogeneity within a slice was investigated. Three patients had MRI post-implant to check urethral position and dosimetry.nnnRESULTSnThe urethra appears larger when defined with gel rather than when defined with a catheter, with volumes of 0.9+/-0.3 [range: 0.6-1.6]cc and 0.7+/-0.2 [range: 0.4-1.0]cc, respectively. Catheter plans appear dosimetrically slightly preferable to gel plans with V(100) prostate being 99.7+/-0.2 [range: 99.3-100.0]% and 99.5+/-0.5 [range: 98.12-99.9]% for catheter and gel, respectively (p=0.048). The urethra appears to receive a higher dose when defined with gel with V(150) being 0.5+/-0.7 [range: 0-2.8]% and 0.2+/-0.2 [range: 0-2.6]% for gel- and catheter-defined urethras. Seed density, COIN and number of seeds were almost equivalent. Statistically, only V(100) prostate and D(90) prostate are significantly different. Putting the catheter plan on the gel image set shows a significant increase in urethral dose with V(150) urethra increasing significantly from 0.2+/-0.2 [range: 0-0.6]% from the catheter plan to 15.3+/-11.9 [range: 0.8-47.0]% for the catheter plan on gel image set (p<0.001). D(90) for the inner core of gel and catheter plans was 193.9+/-6.7 [range: 180.3-202.3]Gy and 198.7+/-4.7 [range: 190.7-211.5]Gy (p=0.023). Gel plans are cooler centrally and less homogeneous, which could be counteracted by increasing seed activity and/or prescription dose, though the clinical significance of this should be investigated before implementation.nnnCONCLUSIONSnThis investigation has shown that the urethral position is distorted by the presence of a urinary catheter. The dosimetry may be different from that planned if this is not taken into account.