Volumetric tumor burden and its effect on brachial plexus dosimetry in head and neck intensity-modulated radiotherapy

To determine the effect of gross tumor volume of the primary (GTV-P) and nodal (GTV-N) disease on planned radiation dose to the brachial plexus (BP) in head and neck intensity-modulated radiotherapy (IMRT). Overall, 75 patients underwent definitive IMRT to a median total dose of 69.96 Gy in 33 fractions. The right BP and left BP were prospectively contoured as separate organs at risk. The GTV was related to BP dose using the unpaired t-test. Receiver operating characteristics curves were constructed to determine optimized volumetric thresholds of GTV-P and GTV-N corresponding to a maximum BP dose cutoff of > 66 Gy. Multivariate analyses were performed to account for factors associated with a higher maximal BP dose. A higher maximum BP dose (> 66 vs ≤ 66 Gy) correlated with a greater mean GTV-P (79.5 vs 30.8 cc; p = 0.001) and ipsilateral GTV-N (60.6 vs 19.8 cc; p = 0.014). When dichotomized by the optimized nodal volume, patients with an ipsilateral GTV-N ≥ 4.9 vs < 4.9 cc had a significant difference in maximum BP dose (64.2 vs 59.4 Gy; p = 0.001). Multivariate analysis confirmed that an ipsilateral GTV-N ≥ 4.9 cc was an independent predictor for the BP to receive a maximal dose of > 66 Gy when adjusted individually for BP volume, GTV-P, the use of a low anterior neck field technique, total planned radiation dose, and tumor category. Although both the primary and the nodal tumor volumes affected the BP maximal dose, the ipsilateral nodal tumor volume (GTV-N ≥ 4.9 cc) was an independent predictor for high maximal BP dose constraints in head and neck IMRT.     

Volumetric-modulated arc radiotherapy for pancreatic malignancies: Dosimetric comparison with sliding-window intensity-modulated radiotherapy and 3-dimensional conformal radiotherapy

Volumetric-modulated arc radiotherapy (VMAT) is an iteration of intensity-modulated radiotherapy (IMRT), both of which deliver highly conformal dose distributions. Studies have shown the superiority of VMAT and IMRT in comparison with 3-dimensional conformal radiotherapy (3D-CRT) in planning target volume (PTV) coverage and organs-at-risk (OARs) sparing. This is the first study examining the benefits of VMAT in pancreatic cancer for doses more than 55.8 Gy. A planning study comparing 3D-CRT, IMRT, and VMAT was performed in 20 patients with pancreatic cancer. Treatments were planned for a 25-fraction delivery of 45 Gy to a large field followed by a reduced-volume 8-fraction external beam boost to 59.4 Gy in total. OARs and PTV doses, conformality index (CI) deviations from 1.0, monitor units (MUs) delivered, and isodose volumes were compared. IMRT and VMAT CI deviations from 1.0 for the large-field and the boost plans were equivalent (large field: 0.032 and 0.046, respectively; boost: 0.042 and 0.037, respectively; p > 0.05 for all comparisons). Both IMRT and VMAT CI deviations from 1.0 were statistically superior to 3D-CRT (large field: 0.217, boost: 0.177; p < 0.05 for all comparisons). VMAT showed reduction of the mean dose to the boost PTV (VMAT: 61.4 Gy, IMRT: 62.4 Gy, and 3D-CRT: 62.3 Gy; p < 0.05). The mean number of MUs per fraction was significantly lower for VMAT for both the large-field and the boost plans. VMAT delivery time was less than 3 minutes compared with 8 minutes for IMRT. Although no statistically significant dose reduction to the OARs was identified when comparing VMAT with IMRT, VMAT showed a reduction in the volumes of the 100% isodose line for the large-field plans. Dose escalation to 59.4 Gy in pancreatic cancer is dosimetrically feasible with shorter treatment times, fewer MUs delivered, and comparable CIs for VMAT when compared with IMRT.     

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.     

Volumetric-modulated arc therapy in postprostatectomy radiotherapy patients: A planning comparison study

The purpose of this study was to compare postprostatectomy planning for volumetric-modulated arc therapy (VMAT) with both single arc (SA) and double arcs (DA) against dynamic sliding window intensity-modulated radiotherapy (IMRT). Ten cases were planned with IMRT, SA VMAT, and DA VMAT. All cases were planned to achieve a minimum dose of 68 Gy to 95% of the planning target volume (PTV) and goals to limit rectal volume >40 Gy to 35% and >65 Gy to 17%, and bladder volumes >40 Gy to 50% and >65 Gy to 25%. Plans were averaged across the 10 patients and compared for mean dose, conformity, homogeneity, rectal and bladder doses, and monitor units. The mean dose to the clinical target volume and PTV was significantly higher (p<0.05) for SA compared with DA or IMRT. The homogeneity index was not significantly different: SA = 0.09; DA = 0.08; and IMRT = 0.07. The rectal V40 was lowest for the DA plan. The rectal V20 was significantly lower (p<0.05) for both the VMAT plans compared with IMRT. There were no significant differences for bladder V40 or rectal and bladder V65. The IMRT plans required 1400 MU compared with 745 for DA and 708 for SA. This study shows that for equivalent dose coverage, SA and DA VMAT plans result in higher mean doses to the clinical target volume and PTV. This greater dose heterogeneity is balanced by improved low-range rectal doses and halving of the monitor units.     

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.     

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.     

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.     

Superior liver sparing by combined coplanar/noncoplanar volumetric-modulated arc therapy for hepatocellular carcinoma: A planning and feasibility study

Compared with step-and-shoot intensity-modulated radiotherapy (sIMRT) and tomotherapy, volumetric-modulated arc therapy (VMAT) allows additional arc configurations in treatment planning and noncoplanar (NC) delivery. This study was first to compare VMAT planning with sIMRT planning, and the second to evaluate the toxicity of coplanar (C)/NC-VMAT treatment in patients with hepatocellular carcinoma (HCC). Fifteen patients with HCC (7 with left-lobe and 8 with right-lobe tumors) were planned with C-VMAT, C/NC-VMAT, and sIMRT. The median total dose was 49 Gy (range: 40 to 56 Gy), whereas the median fractional dose was 3.5 Gy (range: 3 to 8 Gy). Different doses/fractionations were converted to normalized doses of 2 Gy per fraction using an α/β ratio of 2.5. The mean liver dose, volume fraction receiving more than 10 Gy (V10), 20 Gy (V20), 30 Gy (V30), effective volume (V_eff), and equivalent uniform dose (EUD) were compared. C/NC-VMAT in 6 patients was evaluated for delivery accuracy and treatment-related toxicity. Compared with sIMRT, both C-VMAT (p = 0.001) and C/NC-VMAT (p = 0.03) had significantly improved target conformity index. Compared with C-VMAT and sIMRT, C/NC-VMAT for treating left-lobe tumors provided significantly better liver sparing as evidenced by differences in mean liver dose (p = 0.03 and p = 0.007), V10 (p = 0.003 and p = 0.009), V20 (p = 0.006 and p = 0.01), V30 (p = 0.02 and p = 0.002), V_eff (p = 0.006 and p = 0.001), and EUD (p = 0.04 and p = 0.003), respectively. For right-lobe tumors, there was no difference in liver sparing between C/NC-VMAT, C-VMAT, and sIMRT. In all patients, dose to more than 95% of target points met the 3%/3 mm criteria. All 6 patients tolerated C/NC-VMAT and none of them had treatment-related ≥ grade 2 toxicity. The C/NC-VMAT can be used clinically for HCC and provides significantly better liver sparing in patients with left-lobe tumors.     

Efficacy of high-dose-rate interstitial brachytherapy in patients with oral tongue carcinoma

PurposeTo evaluate the results of high-dose-rate (HDR)-interstitial brachytherapy (ISBT) in oral tongue carcinomas.Methods and MaterialsBetween September 1999 and August 2007, 50 patients were treated for oral tongue carcinoma with HDR-ISBT. The patient's mean age was 58 years. Forty-two patients were in T1–2 stage and 8 patients were in T3 stage; 16 patients were in N+ stage and 34 patients in N0 stage. Exclusive ISBT was given to 17 patients (34%) in T1–2 N0 stage and complementary to external beam radiotherapy (EBRT) to 33 patients (66%). A perioperative technique was performed on 14 patients. The median total dose was 44 Gy when HDR was used alone (4 Gy per fraction) and 18 Gy when complementary to 50 Gy EBRT (3 Gy per fraction).ResultsThe median followup was 44 months. Actuarial disease-free survival rates at 3 and 5 years were 81% and 74%, respectively. Local failure developed in 7 patients. Actuarial local control (LC) rates were 87% and 79% at 3 and 5 years in T1–2 stage 94.5% and 91% and T3 stage 43% and 43% (with salvage surgery). Exclusive HDR cases showed LC in 100% of the cases, and the combined group (EBRT + HDR) showed LC in 80% and 69% of the cases at 3 and 5 years (p = 0.044). Soft-tissue necrosis developed in 16% and bone necrosis in 4% of the cases.ConclusionsHDR brachytherapy is an effective method for the treatment of oral tongue carcinoma in low-risk cases. Doses per fraction between 3 and 4 Gy yield LC and complication rates similar to low-dose rate. The perioperative technique promises encouraging results.     

Interstitial brachytherapy as boost for locally advanced T4 head and neck cancer

PurposeLocally advanced squamous cell cancers of the head and neck (SCCHN) with bone and cartilage invasion (BCI) or those with soft-tissue invasion (STI) have been treated with resection followedup with chemoradiotherapy (CRT) or definitive CRT. However, locoregional recurrence remained a large component of treatment failure. High-dose-rate interstitial brachytherapy (BT) has been used for dose escalation to further prevent local relapse. This is a review of our experience.Methods and MaterialsT4N0-3M0 locally advanced oral cavity and oropharyngeal squamous cell carcinoma (SCCA) patients underwent definitive CRT or radiotherapy (RT) followedup with brachytherapy (BT). RT doses ranged from 45 to 50.4 Gy. The patients were reassessed at this dose and if response was inadequate, patients underwent BT. BT doses ranged from 24 to 30 Gy at 3–4 Gy per fraction BID with 6 h in between fractions. Concurrent chemotherapy was platinum based.ResultsTwenty patients were treated with CRT or RT alone followed by BT. Thirteen patients had STI and 7 had BCI; 14 patients were treated with CRT followed by BT; and 6 patients were treated with RT alone followed by BT. Five-year locoregional control was 61%. Five-year overall survival was 29%. When we excluded the patients treated with RT alone, 5-year overall survival was 36%. Nodal status was the only prognostic factor.ConclusionsThis study suggests CRT followedup with BT for patients with T4 locally advanced SCCHN of the oral cavity, and oropharynx is a feasible treatment option. In patients with poor response to CRT, BT may be used for dose escalation to increase locoregional control.     

Effect of induction chemotherapy on estimated risk of radiation pneumonitis in bulky non–small cell lung cancer

Patients with bulky non–small cell lung cancer (NSCLC) may be at a high risk for radiation pneumonitis (RP) if treated with up-front concurrent chemoradiation. There is limited information about the effect of induction chemotherapy on the volume of normal lung subsequently irradiated. This study aims to estimate the reduction in risk of RP in patients with NSCLC after receiving induction chemotherapy. Between 2004 and 2009, 25 patients with Stage IV NSCLC were treated with chemotherapy alone (no surgery or radiation therapy [RT]) and had computed tomography (CT) scans before and after 2 cycles of chemotherapy. Simulated RT plans were created for the prechemotherapy and postchemotherapy scans so as to deliver 60 Gy to the thoracic disease in patients who had either a >20% volumetric increase or decrease in gross tumor volume (GTV) from chemotherapy. The prechemotherapy and postchemotherapy scans were analyzed to compare the percentage of lung volume receiving≥20 Gy (V20), mean lung dose (MLD), and normal tissue complication probability (NTCP). Eight patients (32%) had a GTV reduction >20%, 2 (8%) had GTV increase >20%, and 15 (60%) had stable GTV. In the 8 responders, there was an absolute median GTV decrease of 88.1 cc (7.3 to 351.6 cc) or a 48% (20% to 62%) relative reduction in tumor burden. One had >20% tumor progression during chemotherapy, yet had an improvement in dosimetric parameters postchemotherapy. Among these 9 patients, the median decrease in V20, MLD, and NTCP was 2.6% (p<0.01), 2.1 Gy (p<0.01), and 5.6% (p<0.01), respectively. Less than one-third of patients with NSCLC obtain >20% volumetric tumor reduction from chemotherapy alone. Even with that amount of volumetric reduction, the 5% reduced risk of RP was only modest and did not convert previously ineligible patients to safely receive definitive thoracic RT.     

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.     

Evaluation of bolus electron conformal therapy compared with conventional techniques for the treatment of left chest wall postmastectomy in patients with breast cancer

Postmastectomy radiation (PMRT) lowers local-regional recurrence risk and improves survival in selected patients with breast cancer. The chest wall and lower axilla are technically challenging areas to treat with homogenous doses and normal tissue sparing. This study compares several techniques for PMRT to provide data to guide selection of optimal treatment techniques. Twenty-five consecutive left-sided patients treated postmastectomy were contoured using Radiation Therapy Oncology Group (RTOG) atlas guidelines then planned using 4 different PMRT techniques: opposed tangents with wedges (3-dimensional [3D] wedges), opposed tangents with field-in-field (FiF) modulation, 8-field intensity modulation radiotherapy (IMRT), and custom bolus electron conformal therapy (BolusECT, .decimal, Inc., Sanford, FL). Required planning target volume (PTV) coverage was held constant, and then dose homogeneity and normal tissue dose parameters were compared among the 4 techniques. BolusECT achieved clincally acceptable PTV coverage for 22 out of 25 cases. Compared with either tangential technique, IMRT and BolusECT provided the lowest heart V₂₅ doses (3.3% ± 0.9% and 6.6% ± 3.2%, respectively with p < 0.0001). FiF had the lowest mean total lung dose (7.3 ± 1.1 Gy, with p = 0.0013), IMRT had the lowest total lung V₂₀ (10.3% ± 1.6%, p < 0.0001), and BolusECT had the lowest mean heart dose (7.3 ± 2.0 Gy, p = 0.0002). IMRT provided the optimal dose homogeneity and normal tissue sparing compared with all other techniques for the cases in which BolusECT could not achieve acceptable PTV coverage. IMRT generally exposes contralateral breast and lung to slightly higher doses. Optimal PMRT technique depends upon patient anatomy. Patients whose maximal target volume depth is about 5.7 cm or less can be treated with BolusECT-assisted 12 or 15 MeV electron beams. At these energies, BolusECT has comparable dose-volume statistics as IMRT and lower heart V₂₅ than opposed tangential beams. Patients with larger depths are best treated with IMRT, which provides significant advantages in both dose homogeneity and normal tissue sparing compared with all other techniques.     

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.     

Prostate gland edema after single-fraction high-dose rate brachytherapy before external beam radiation therapy

PurposeHigh–dose rate brachytherapy (HDRB) is frequently used as a boost to external beam radiation therapy (EBRT) in prostate cancer patients. With the increasing use of small planning target volume margins in EBRT, prostatic edema induced by HDRB can be a contributing factor to geometric miss when HDRB is performed before or during EBRT. We assessed prostate gland volumetric change after single-fraction HDRB and its impact on definition of treatment volume for EBRT.Methods and MaterialsThirty-one consecutive patients with intermediate-risk prostate cancer treated with single-fraction HDRB (10 Gy) combined with hypofractionated EBRT were analyzed. A second CT scan was performed 7 days after HDRB, and images were coregistered with the planning CT scan that contained the original clinical target volume (CTV). The post-HDRB prostate CTV volume was compared with the original CTV by a single observer.ResultsAll patients presented volumetric variation. In most cases (68%), the prostate increased in volume, whereas it decreased in 32%. The mean prostatic volume was 42.2 cc before HDRB and 43.6 cc after HDRB, representing a mean volume difference of 3.4%, ranging from ?14.2% to 23.8% (p = 0.756). This difference is the result of mean changes of 0.6 mm (?6.1 to 6.6) in the anterior–posterior, 0.5 mm (?5.5 to 3.0) in the lateral, and 0.2 mm (?5.0 to 5.0) in the superior–inferior axes.ConclusionsAlthough a nonsignificant volumetric change occurs after single-fraction HDRB, individual variations on specific axis could lead to important uncertainties during EBRT.     

Circumferential or sectored beam arrangements for stereotactic body radiation therapy (SBRT) of primary lung tumors: Effect on target and normal-structure dose-volume metrics

To compare 2 beam arrangements, sectored (beam entry over ipsilateral hemithorax) vs circumferential (beam entry over both ipsilateral and contralateral lungs), for static-gantry intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) delivery techniques with respect to target and organs-at-risk (OAR) dose-volume metrics, as well as treatment delivery efficiency. Data from 60 consecutive patients treated using stereotactic body radiation therapy (SBRT) for primary non–small-cell lung cancer (NSCLC) formed the basis of this study. Four treatment plans were generated per data set: IMRT/VMAT plans using sectored (-s) and circumferential (-c) configurations. The prescribed dose (PD) was 60 Gy in 5 fractions to 95% of the planning target volume (PTV) (maximum PTV dose ~ 150% PD) for a 6-MV photon beam. Plan conformality, R₅₀ (ratio of volume circumscribed by the 50% isodose line and the PTV), and D_2 cm (D_max at a distance ≥2 cm beyond the PTV) were evaluated. For lungs, mean doses (mean lung dose [MLD]) and percent V₃₀/V₂₀/V₁₀/V₅ Gy were assessed. Spinal cord and esophagus D_max and D₅/D₅₀ were computed. Chest wall (CW) D_max and absolute V₃₀/V₂₀/V₁₀/V_5 Gy were reported. Sectored SBRT planning resulted in significant decrease in contralateral MLD and V₁₀/V_5 Gy, as well as contralateral CW D_max and V₁₀/V_5 Gy (all p < 0.001). Nominal reductions of D_max and D₅/D₅₀ for the spinal cord with sectored planning did not reach statistical significance for static-gantry IMRT, although VMAT metrics did show a statistically significant decrease (all p < 0.001). The respective measures for esophageal doses were significantly lower with sectored planning (p < 0.001). Despite comparable dose conformality, irrespective of planning configuration, R₅₀ significantly improved with IMRT-s/VMAT-c (p < 0.001/p = 0.008), whereas D_2 cm significantly improved with VMAT-c (p < 0.001). Plan delivery efficiency improved with sectored technique (p < 0.001); mean monitor unit (MU)/cGy of PD decreased from 5.8 ± 1.9 vs 5.3 ± 1.7 (IMRT) and 2.7 ± 0.4 vs 2.4 ± 0.3 (VMAT). The sectored configuration achieves unambiguous dosimetric advantages over circumferential arrangement in terms of esophageal, contralateral CW, and contralateral lung sparing, in addition to being more efficient at delivery.