Clinical outcomes of high-dose-rate interstitial gynecologic brachytherapy using real-time CT guidance

PurposeTo evaluate clinical outcomes of CT-guided high-dose-rate (HDR) interstitial brachytherapy for primary and recurrent gynecologic cancer.Methods and MaterialsRecords were reviewed for 68 women (34 with primary disease and 34 with recurrence) treated with CT-guided HDR interstitial brachytherapy between May 2005 and September 2011. Interstitial application was performed under general anesthesia using an iterative approach of catheter insertion and adjustment with serial image acquisition by CT in a dedicated brachytherapy suite. The median fractional brachytherapy dose was 3.9 Gy delivered twice daily in seven fractions. The median cumulative dose in equivalent 2-Gy fractions was 74.8 Gy. Actuarial survival estimates were calculated using the Kaplan–Meier method, and toxicity was reported by Common Toxicity Criteria.ResultsPrimary disease sites were endometrial (34), cervical (17), vaginal (11), ovarian (3), and vulvar (3). Median age was 61.5 years, and tumor size at diagnosis was 3.4 cm. Median D₉₀ and V₁₀₀ were 73.6 Gy and 87.5%, respectively; median D_2cc for bladder, rectum, and sigmoid were 67.1, 64.6, and 53.7 Gy, respectively. With a median followup of 17 months, actuarial rates of local control, progression-free survival, and overall survival at 2 years for all patients were 86%, 60%, and 64%, respectively. There were 9 grade 3 late toxicities (six gastrointestinal and three vulvovaginal).ConclusionsHDR interstitial brachytherapy with CT-guided catheter placement results in acceptable local control, toxicity, and survival rates for women with primary or recurrent gynecologic cancer. Durable pelvic control may be achieved in most patients with this specialized brachytherapy technique.     

Toxicity and early treatment outcomes in low- and intermediate-risk prostate cancer managed by high-dose-rate brachytherapy as a monotherapy

PurposeTo determine the acute and late genitourinary (GU) and gastrointestinal (GI) toxicity and present short-term biochemical no evidence of disease (bNED) rates after high-dose-rate brachytherapy (HDR-B) monotherapy.Methods and MaterialsBetween October 2003 and June 2006, 36 patients with low (28) and intermediate (8) risk prostate cancer (PCA) were treated by HDR-B monotherapy. All patients received one implant and four fractions of 9.5 Gy within 48 h for a total prescribed dose (PD) of 38 Gy. Five patients received hormonal therapy (HT). Median age was 63.5 years and median followup was 3 years (range, 0.4–4 years). Toxicity was scored according to the CTCAE version 3.0. Biochemical failure was defined according to the Phoenix criteria.ResultsAcute and late Grade 3 GU toxicity was observed in 1 (3%) and 4 (11%) patients, respectively. Grade 3 GI toxicity was absent. The three- year bNED survival rate was 100%. The sexual preservation rate in patients without HT was 75%. Late Grade 3 GU toxicity was associated with the planning target volume (PTV) V₁₀₀ (% PTV receiving ≥100% of the PD; p = 0.036), D₉₀ (dose delivered to 90% of the PTV; p = 0.02), and the urethral V₁₂₀ (urethral volume receiving ≥120% of the PD; p = 0.043). The urethral V₁₂₀ was associated with increased PTV V₁₀₀ (p < 0.001) and D₉₀ (p = 0.003).ConclusionsAfter HDR-B monotherapy, late Grade 3 GU toxicity is associated with the urethral V₁₂₀ and the V₁₀₀ and D₉₀ of the PTV. Decrease of the irradiated urethral volume may reduce the GU toxicity and potentially improve the therapeutic ratio of this treatment.     

Interstitial preoperative high-dose-rate brachytherapy for early stage cervical cancer: Dose–volume histogram parameters,pathologic response and early clinical outcome

PurposeTo analyze dose–volume histogram parameters and pathologic response after preoperative high-dose-rate brachytherapy (HDRB) for high-risk early stage cervical cancers (ESCCs).Methods and MaterialsFrom June 2007 to December 2011, 32 patients with a histologically proven invasive cervical cancer with high risk of local recurrence (size >2 cm, adenocarcinoma type, perineural and/or lymphovascular invasion) underwent a preoperative HDRB, which delivered a total dose of 39 Gy in nine fractions over 5 days. All the patients underwent hysterectomy after HDRB.ResultsWith a median clinical target volume of 50 cc (minimum–maximum, 42–74), the median V₁₀₀ was 49 cc (minimum–maximum, 42–50). Median D₉₀ was 45 Gy (equivalent dose at 2 Gy per fraction, 56 Gy_αβ10). Median D_2cc was 34 Gy, 31 Gy, 28 Gy, and 38 Gy_αβ3 for bladder, rectum, sigmoid, and vagina, respectively. Twenty-eight patients (88.5%) achieved a complete histologic response after surgery, whereas for the 4 remaining patients, residual tumor cells (3 patients) and gross residual disease (1 patient) were observed in the pathologic specimen. With a median followup of 24 months (minimum–maximum, 5–48), no local recurrence was observed; 1 patient died of intercurrent cause. Early toxicity occurred within the 30 days after HDRB (Common Terminology Criteria for Adverse Events v3.0) was G1 diarrhea for 15 patients (47%) and G1 urinary frequency or urgency for 13 patients (40.6%). No G2–G3 toxicities were noticed.ConclusionsPreoperative HDRB for high-risk ESCCs represents a well-tolerated procedure, which leads to a high rate of postoperative pathologic response. Dose–volume histogram parameters were at least equivalent to those obtained with a low-dose-rate procedure. Long-term results will help to analyze the place of preoperative brachytherapy in the management of high-risk ESCCs.     

Urethral dosimetry and toxicity with high-dose-rate interstitial brachytherapy for vaginal cancer

PurposeThe tolerance and complication rates of the urethra are unknown for the interstitial high-dose-rate brachytherapy (HDR-BT) for vaginal cancer.Methods and MaterialsPatients with vaginal cancer near/involving the urethra who were treated with HDR-BT between 2008 and 2011 were included. Patients received mean external beam dose of 48.0 Gy followed by mean HDR-BT dose of 4.5 Gy/fraction for five fractions. With CT-based planning, the urethra was contoured from the bladder neck to the meatus. Doses were converted to the biologically equivalent dose in 2 Gy/fraction (EQD₂).ResultsA total of 16 patients were included, and the EQD₂ D₉₀ was 74.9 Gy. The urethral volume was 1.31 cm³, and the EQD₂ to 0.1 and 1 cm³ were 76.2 and 48.9 Gy, respectively. Two of the 6 patients with urethral involvement developed urethral necrosis. The D₉₀ for these 2 patients was 76.8 Gy, and the urethral doses to 0.1 and 1 cm³ were 95.1 and 45.8, respectively. Those who developed severe urethral toxicity had a trend to urethral EQD₂ (95.1 Gy vs. 73.4 Gy, p = 0.1) and significantly higher dose per fraction of HDR-BT to 0.1 cm³ of the urethra (5.7 Gy vs. 3.7 Gy, p = 0.02) when compared with those who did not develop severe urethral toxicity.ConclusionsThis study is among the first to assess urethral dosimetry for patients treated with HDR-BT for vaginal cancer. Patients who received five fractions of higher than 5 Gy/fraction to 0.1 cm³ of urethra (estimated EQD₂ of 85 Gy) are at increased risk of severe urethral toxicity.     

Interstitial brachytherapy vs. intensity-modulated radiation therapy for patients with cervical carcinoma not suitable for intracavitary radiation therapy

PurposeInterstitial brachytherapy (IBT) is the standard alternative treatment for patients with cervical carcinoma not suitable for intracavitary radiotherapy. There is an emerging belief that intensity-modulated radiotherapy (IMRT) has the potential to replace IBT. We aimed to compare the dosimetry achieved by IBT and IMRT in such patients.Methods and MaterialsThe CT imaging data, previously used for IBT planning of 12 patients with cervical carcinoma, were transferred to IMRT planning system to generate parallel IMRT plans. Prescribed dose to the planning target volume (PTV) was 20 Gy delivered in 2-weekly high-dose-rate fractions of 10 Gy each with IBT (biologically equivalent dose [BED₁₀] 40 Gy) and 33 Gy/13 fractions/2.5 wk with IMRT (BED₁₀ 41 Gy). For comparison, dose–volume parameters for target and organs at risk were recorded and expressed in terms of BED₁₀ and BED₃, respectively.ResultsFor PTV, the mean D₉₅ (dose received by 95% of PTV) was better with IBT (57.16 Gy vs. 41.47 Gy, p = 0.003). The mean conformity index was 0.94 and 0.90 with IBT and IMRT, respectively (p = 0.034). IBT delivered significantly reduced doses to 1.0 cc (D_max), 5.0 cc (D_{5 cc}), 50% (D₅₀), and 75% (D₇₅) of bladder volume as compared with IMRT. The mean rectal D_max was significantly better with IBT as compared with IMRT (54.64 Gy vs. 62.63 Gy, p = 0.02).ConclusionsIBT provides superior PTV coverage and organs at risk sparing to IMRT. Thus, IBT remains the standard treatment for patients with cervical carcinoma unsuitable for intracavitary radiotherapy.     

First report on the use of a thinner 125I radioactive seed within 20-gauge needles for permanent radioactive seed prostate brachytherapy: Evaluation of postimplant dosimetry and acute toxicity

PurposeTo compare postoperative dosimetry and acute toxicity of new 0.5-mm ¹²⁵I seeds in 20-gauge (20G) diameter prostate brachytherapy (PB) needles with standard 0.8-mm seeds in 18G needles.Methods and MaterialsPostoperative dosimetry was performed on 100 consecutive PB patients treated with ThinSeeds in 20G needles and compared with 100 consecutively treated PB patients using standard-sized seeds and needles (18G). Dosimetry was performed on postoperative Day 1 CT scans. Acute urinary retention was also compared between these two groups. Acute toxicity was evaluated in 22 consecutively treated patients with thinner seeds/needles and compared with 22 consecutive concurrent patients treated with standard seeds and needles. All patients were evaluated by pre- and post-PB self-administered surveys, physical examinations on post-PB Day 1, and telephone surveys on Day 7. Endpoints included dysuria, acute urinary retention, hematuria, perineal pain/bruising, and International Prostate Symptom Score.ResultsPost-PB dosimetric comparison demonstrated that the V₁₀₀ (95% vs. 91%), D₉₀ (161 Gy vs.149 Gy), V₁₅₀ (55% vs. 45%), and RV₁₀₀ (0.43 cc vs. 0.30 cc) were significantly (p < 0.0004) higher in the 20G group. Urinary retention rates were 8% and 7% and median catheter-dependent durations were 7 and 14 days for the 20G and 18G groups, respectively. No significant differences were found for dysuria, hematuria, or International Prostate Symptom Score. Post-PB Day 1 perineal bruising and pain scores on Days 1 and 7 were significantly less (p < 0.04) in 20G cohort.ConclusionsSmaller diameter needles and seeds resulted in improved post-PB Day 1 V₁₀₀ and D₉₀ dosimetry, and significantly less acute perineal pain and bruising.     

Electronic brachytherapy for postsurgical adjuvant vaginal cuff irradiation therapy in endometrial and cervical cancer: A retrospective study

PurposeA new platform for brachytherapy called electronic brachytherapy (EBT) has been developed, which uses a miniature X-ray source to generate low-energy radiation. A retrospective study of adverse events and clinical outcomes in patients treated with EBT to the vaginal cuff, either as monotherapy or in combination with external beam radiation therapy (EBRT), was conducted.Methods and MaterialsMedical records were reviewed from 16 patients treated with postoperative EBT for endometrial (n = 13) or cervical cancer (n = 3) between February 2009 and November 2010. Patients received either intracavitary vaginal EBT alone or EBT in combination with EBRT. The radiobiologic effectiveness of EBT was assumed to be one.ResultsMedian follow-up was 20.5 months (range, 7–36 months). When EBT was used alone (n = 5), the median dose per fraction, number of fractions, and total dose delivered were: 6 Gy (range, 5.5–6.2 Gy), 5 fractions (range, 5–6), and 30 Gy (range, 30–34 Gy), respectively. When EBT was combined with EBRT, the EBT component median dose per fraction, number of fractions, and total dose delivered were: 5 Gy (range, 4.5–7 Gy), 2 fractions (range, 2–4), and 14 Gy (range, 9–20 Gy), respectively. The median EBRT dose was 45 Gy (range, 45–49.2 Gy). Our local control rate, locoregional (pelvic) control rate, and overall survival rate were 94%, 94%, and 88%, respectively. Of the 16 patients, 4 patients reported Grade 2 or greater toxicity (25%); however, there were no Grade 4–5 adverse events. Gynecologic, genitourinary, and gastrointestinal adverse events accounted for 57% (n = 4), 43% (n = 3), and 0% (n = 0) of all Grade 2 or greater side effects. No Grade 2 or higher toxicities were noted in patients treated with EBT alone.ConclusionEBT is an acceptable means of delivering postoperative vaginal brachytherapy and appears comparable with other methods; as the sole method of treatment, the toxicity rates of EBT are low.     

Reirradiation of paraaortic lymph node metastasis by brachytherapy with hyaluronate injection via paravertebral approach: With DVH comparison to IMRT

Purpose/IntroductionTo safely irradiate retroperitoneal targets as paraaortic lymph node by separating abdominal at-risk organs from the target during irradiation, we created a percutaneous paravertebral approach of high-dose-rate brachytherapy with hyaluronate gel injection (HGI). We report a case treated with this technique.Methods and MaterialsWe encountered a patient with symptomatic regrowth of paraaortic lymph node metastasis from prostatic cancer. He had previously received 58.4 Gy of radiotherapy to the same region 12 months prior. Brachytherapy needles and a HGI needle were deployed via the paravertebral approach under local anesthesia at our outpatient clinic.ResultsA single dose of 22.5 Gy (equivalent to 60.94 Gy in 2 Gy per fraction schedule calculated at α/β = 10) was delivered to the target, with preservation of the surrounding small intestine by HGI with D_2cc (minimum dose to the most irradiated volume of 2 mL) of 5.05 Gy. Therapeutic ratio was 3.64 times higher for this brachytherapy plan compared with an intensity-modulated radiation therapy plan. At followup at 1 year after brachytherapy, the symptoms had disappeared, tumor size had reduced with no fluorodeoxyglucose accumulation, and prostate-specific antigen level had decreased.ConclusionWe consider that high-dose-rate brachytherapy with the HGI procedure offers effective treatment even in this type of reirradiation situation.     

Dosimetric comparison of multichannel with one single-channel vaginal cylinder for vaginal cancer treatments with high-dose-rate brachytherapy

PurposeTo compare the three-dimensional (3D) image (CT/MR)-based planning with a multichannel vaginal cylinder (MVC) to a single-channel vaginal cylinder (SVC) for the treatment of vaginal cancer.Methods and MaterialsA total of 20 consecutive patients were treated with 3D CT/MR image-based high-dose-rate (HDR) brachytherapy using an MVC. All patients received external beam radiation therapy before HDR brachytherapy. A brachytherapy dose of 20–25 Gy of more than five fractions was delivered to clinical target volume (CTV). Retrospectively, treatment plans for all patients were generated using the central channel only to mimic an SVC applicator. The SVC plans were optimized to match CTV coverage with MVC plans. Dose homogeneity index as well as bladder, rectum, sigmoid, and urethral doses were compared.ResultsThe mean D₉₀ for CTV was 74.2 Gy (range: 48.8–84.1 Gy). The mean (±standard deviation) of dose homogeneity index for MVC vs. SVC was 0.49 (±0.19) and 0.52 (±0.23), respectively (p = 0.09). Mean bladder 0.1, 1, and 2 cc doses for MVC vs. SVC were 69 vs. 71.2 Gy (p = 0.35), 61.4 vs. 63.8 Gy (p = 0.1), and 59.5 vs. 60.9 Gy (p = 0.31), respectively. Similarly, mean rectum 0.1, 1, and 2 cc doses for MVC vs. SVC were 67.2 vs. 75.4 Gy (p = 0.005), 60.0 vs. 65.6 Gy (p = 0.008), and 57.3 vs. 62.0 Gy (p = 0.015), respectively, and mean sigmoid doses were 56.3 vs. 60.5 Gy (p = 0.10), 50.9 vs. 53.1 Gy (p = 0.09), and 49.1 vs. 50.7 Gy (p = 0.10), respectively.ConclusionThe 3D CT-/MR-based plan with MVC may provide better dose distribution in the management of certain clinical situations of vaginal cancer requiring intracavitary brachytherapy, especially in minimizing potential late rectal complications.     

The impact of body mass index on rectal dose in locally advanced cervical cancer treated with high-dose-rate brachytherapy

PurposeThe impact of body mass index (BMI) on rectal dose in brachytherapy for cervical cancer is unknown. We assessed the association of BMI on rectal dose and lower gastrointestinal (GI) toxicity.Methods and MaterialsBetween 2007 and 2010, 51 patients with 97 brachytherapy planning images were reviewed. Volumetric measurements of the maximum percentage, mean percentage, dose to 2cc (D2cc), and dose to 1cc (D1cc) of the rectum, and the Internal Commission on Radiation Units and Measurement (ICRU) rectal point were recorded. Linear mixed effect models, analysis of variance, and regression analyses were used to determine the correlation between multiple observations or to detect a difference in the mean. The GI acute and late toxicity were prospectively recorded and retrospectively analyzed.ResultsThe average BMI (kg/m²) was 27.7 with a range of 17.4–46.6. Among the patients, 8% were morbidly obese, 25% obese, 25% overweight, 40% normal weight, and 2% underweight. The mean D1cc, D2cc, mean rectal dose (%), maximum rectal dose (%), and ICRU rectum was 3.03 Gy, 2.78 Gy, 20%, 60%, and 2.99 Gy, respectively. On multivariate analysis, there was a significant decrease in the D1cc and D2cc rectal dose (p = 0.016), ICRU rectal point dose (p = 0.022), and mean rectal dose percentage (p = 0.021) with an increase in BMI. There was, however, no statistically significant relationship between BMI and GI toxicity.ConclusionsObesity decreases the rectal dose given in high-dose-rate brachytherapy for locally advanced cervical cancer because of an increase in fatty tissue in the recto-uterine space. There is no significant correlation between BMI and acute or late GI toxicity.     

Clinical and dosimetric factors associated with acute rectal toxicity in patients treated with 131Cs brachytherapy for prostate cancer

Purpose¹³¹Cs has been recently introduced for use in prostate brachytherapy. We wished to identify clinical and dosimetric factors associated with acute bowel/rectal toxicity in patients treated with ¹³¹Cs.Methods and MaterialsPatients treated with ¹³¹Cs prostate brachytherapy at the University of Pittsburgh were asked to complete expanded prostate cancer index composite surveys preoperatively and at 2–4 weeks and 3 months postimplant. We identified patients who experienced acute and persistent acute bowel toxicity to determine if any factors could correlate with either situation.ResultsOne hundred six patients were treated with ¹³¹Cs from September 2006 to May 2008. Thirty-eight percent of patients met our criteria for patient-appreciated acute bowel symptoms. On multivariate analysis, the volume of rectum receiving 50% of the prescribed dose (R-V₅₀; 4.1 vs. 2.6 cc, p = 0.01), R-V₇₅ (1.3 vs. 0.62 cc, p = 0.01), the percentage of the prescribed dose received by 1 cc of the rectum (R-D-1cc; 75% vs. 64%, p = 0.02), and R-D-2cc (63% vs. 54%, p = 0.003) were found to be factors associated with a greater risk of severe acute bowel toxicity. At 3-month followup, 28% of patients had persistent acute bowel toxicity. On multivariate analysis, no factors were identified that correlated with persistent acute bowel toxicity.ConclusionsThis study identifies R-V₅₀, R-V₇₅, R-D-1cc, and R-D-2cc as factors associated with patient-appreciated acute rectal toxicity. We are performing dosimetric analysis to determine the optimal distance for the posterior needles from the prostate–rectal interface to decrease rectal dose while still maintaining adequate coverage of prostate.     

Re-irradiation with interstitial pulsed-dose-rate brachytherapy for unresectable recurrent head and neck carcinoma

PurposeTo assess the long-term results of protocol-based interstitial pulsed-dose-rate (PDR) brachytherapy combined with simultaneous chemotherapy in selected patients with recurrent head and neck tumors not amenable to salvage surgery.Methods and MaterialsA total of 51 patients with recurrent head and neck cancer were treated with interstitial PDR brachytherapy. Forty patients (78%) had salvage brachytherapy alone using a median total dose of 60 Gy. Salvage brachytherapy in combination with external beam therapy was performed in 11 patients (22%) using a median total dose of D_REF = 27 Gy. Simultaneously with the PDR brachytherapy, a concomitant chemotherapy was administered in 35/51 (69%) of patients. The analysis was performed after a median followup of 58 months.ResultsLocal control rates calculated according to Kaplan–Meier after 2 and 5 years were 71% and 57%, respectively. Comparing results of salvage PDR brachytherapy with or without simultaneous chemotherapy, the 5-year local recurrence-free survival rates were 78.9% vs. 38.5% (p = 0.01), respectively. No other patient or treatment-related parameters had a significant influence on treatment results. A total of 9/51 (17.7%) and 6/51 (11.8%) patients developed soft-tissue necrosis or bone necrosis, respectively, but only 2% of patients required surgical treatment.ConclusionsPDR interstitial brachytherapy with pulse doses between 0.4 and 0.7 Gy/h/24 h with simultaneous chemotherapy is an effective and safe option for curative therapy in selected patients with head and neck cancer in previously irradiated areas, which are not suitable for salvage surgery.     

Multi-parametric MRI-guided focal tumor boost using HDR prostate brachytherapy: A feasibility study

PurposeThis study investigates the feasibility of delivering focal boost dose to tumor regions, identified with multi-parametric MRI, in high-dose-rate prostate brachytherapy.Methods and MaterialsT2-weighted, diffusion-weighted, and dynamic-contrast-enhanced MRI were acquired the day before treatment and analyzed retrospectively for 15 patients. Twelve patients had hormone therapy before the MRI scan. The tumor was delineated on MRI by a radiologist and registered to treatment planning transrectal ultrasound images. A margin based on analysis of delineation and registration uncertainties was applied to create a focal boost planning target volume (F-PTV). Delivered treatment plans were compared with focal boost plans optimized to increase F-PTV dose as much as allowed by urethral and rectal dose constraints.ResultsTumors were delineated in all patients with volumes 0.4–23.0 cc. The margin for tumor delineation and image registration uncertainties was estimated to be 4.5 mm. For F-PTV, the focal boost treatment plans increased median D₉₀ from 17.6 to 20.9 Gy and median V₁₅₀ from 27.3% to 75.9%.ConclusionsMRI-guided high-dose-rate prostate brachytherapy focal tumor boost is feasible—tumor regions can be identified even after hormone therapy, and focal boost dose can be delivered without violating urethral and rectal dose constraints.     

Brachytherapy provides comparable outcomes and improved cost-effectiveness in the treatment of low/intermediate prostate cancer

PurposeTo evaluate the cost-effectiveness and outcomes of low-dose-rate (LDR) and high-dose-rate (HDR) brachytherapy compared with intensity-modulated radiation therapy (IMRT) in patients with low/intermediate risk of prostate cancer.Methods and MaterialsOne thousand three hundred twenty-eight patients with low or intermediate risk of prostate cancer were treated with LDR (n = 207), HDR with four fractions (n = 252), or IMRT (n = 869) between January 1992 and December 2008. LDR patients were treated with palladium seeds to a median dose of 120 Gy, whereas HDR patients were treated to a median dose 38.0 Gy (four fractions). IMRT patients received 42–44 fractions with a median dose of 75.6 Gy. Clinical outcomes were compared, including biochemical failure, cause-specific survival, and overall survival.ResultsOverall, no differences in 5-year biochemical control (BC) or cause-specific survival were noted among treatment modalities. The calculated reimbursement for LDR brachytherapy, HDR brachytherapy with four fractions, and IMRT was $9,938; $17,514; and $29,356, respectively. HDR and LDR brachytherapy were statistically less costly to Medicare and the institution than IMRT (p < 0.001), and LDR brachytherapy was less costly than HDR brachytherapy (p = 0.01 and p < 0.001). Incremental cost-effectiveness ratios for cost to Medicare for BC with IMRT were $4045 and $2754 per percent of BC for LDR and HDR brachytherapy, respectively. Incremental cost-effectiveness ratio using institutional cost comparing IMRT with LDR and HDR brachytherapy was $4962 and $4824 per 1% improvement in BC.ConclusionsIn this study of patients with low and intermediate risk of prostate cancer, comparable outcomes at 5 years were noted between modalities with increased costs associated with IMRT.     

Dosimetric and clinical outcome in image-based high-dose-rate interstitial brachytherapy for anal cancer

PurposeTo evaluate dosimetric and clinical outcome in patients of anal cancer treated with image-based interstitial high-dose-rate brachytherapy following chemoradiation.Methods and MaterialsSixteen patients with anal cancer were treated with chemoradiation followed by brachytherapy boost with image-based high-dose-rate interstitial brachytherapy from January 2007 to June 2011. Two brachytherapy dose schedules were used: 21 Gy in seven fractions and 18 Gy in six fractions depending on response to chemoradiation. CT scan was done after placement of needles for confirmation of placement and treatment planning. Target volume was contoured on CT scans. Volumetric quality indices and dose parameters were calculated.ResultsThe mean clinical target volume was 17.7 ± 4.98 cm³, and the median overall tumor size was 4.2 cm (3.4–5 cm). The mean values of coverage index, dose homogeneity index, overdose volume index, dose non-uniformity ratio, and conformal index were 0.94, 0.83, 0.21, 0.37, and 0.88, respectively. With a median followup of 41 months (range, 20–67.2 months), preservation of the anal sphincter was achieved in 14 patients. The 1- and 2-year local control rates were 93.8% and 87.5%, respectively. Treatment was well tolerated and none of the patients developed Grade 3 or higher late toxicity.ConclusionsThe combination of external beam radiotherapy with interstitial brachytherapy increases the dose to the tumor volume and limits the volume of irradiated normal tissue, thereby decreasing late toxicity. The use of image-based treatment planning provides better dose conformality with reduced toxicity and helps to prevent a geographic miss.     

Improving prostate brachytherapy quality assurance with MRI–CT fusion–based sector analysis in a phase II prospective trial of men with intermediate-risk prostate cancer

PurposeWe combined sector analysis with MRI–CT fusion to comprehensively assess postimplant dosimetry after prostate brachytherapy.Methods and MaterialsSubjects were 50 men with intermediate-risk prostate cancer treated with ¹²⁵I brachytherapy in a prospective phase II clinical trial. On Day 30 after the implantation, dosimetry was evaluated in the prostate base, midgland, and apex regions on fused MRI–CT scans and CT scans. Volumes of each sector receiving 100% of the prescribed dose (V₁₀₀) and doses to 90% of each sector (D₉₀) were also calculated on the ultrasonogram used for treatment planning and compared with values derived from CT and fused MRI–CT scans.ResultsFused MRI–CT scans revealed lower-than-expected doses for the whole prostate (V₁₀₀ = 91.3%, D₉₀ = 152.9 Gy) compared with CT scans (98.5% and 183.6 Gy, p < 0.0001) and lower doses to the prostate base (V₁₀₀ = 79%, D₉₀ = 130 Gy) vs. CT (96% and 170 Gy, p < 0.0001). However, lower doses to the prostate base did not adversely affect biochemical outcomes in men with biopsy-proven disease at the base. At a median followup time of 42 months, the mean prostate-specific antigen level for all patients was 0.3 ng/mL, and no patient had experienced biochemical or clinical progression or recurrence.ConclusionsMRI–CT fusion–based sector analysis was feasible and revealed significantly lower doses to the prostate base than doses estimated from CT alone, although this did not affect biochemical outcomes. MRI–CT fusion–based sector analysis may be useful for developing MRI-based dosimetric markers to predict disease outcomes and treatment-related morbidity.