Feasibility of tomotherapy to reduce normal lung and cardiac toxicity for distal esophageal cancer compared to three-dimensional radiotherapy

Purpose

To compare the effectiveness of tomotherapy and three-dimensional (3D) conformal radiotherapy to spare normal critical structures (spinal cord, lungs, and ventricles) from excessive radiation in patients with distal esophageal cancers.

Materials and methods

A retrospective dosimetric study of nine patients who had advanced gastro-esophageal (GE) junction cancer (7) or thoracic esophageal cancer (2) extending into the distal esophagus. Two plans were created for each of the patients. A three-dimensional plan was constructed with either three (anteroposterior, right posterior oblique, and left posterior oblique) or four (right anterior oblique, left anterior oblique, right posterior oblique, and left posterior oblique) fields. The second plan was for tomotherapy. Doses were 45 Gy to the PTV with an integrated boost of 5 Gy for tomotherapy.

Results

Mean lung dose was respectively 7.4 and 11.8 Gy (p = 0.004) for tomotherapy and 3D plans. Corresponding values were 12.4 and 18.3 Gy (p = 0.006) for cardiac ventricles. Maximum spinal cord dose was respectively 31.3 and 37.4 Gy (p < 0.007) for tomotherapy and 3D plans. Homogeneity index was two for both groups.

Conclusions

Compared to 3D conformal radiotherapy, tomotherapy decreased significantly the amount of normal tissue irradiated and may reduce treatment toxicity for possible dose escalation in future prospective studies.     

Adjuvant radiotherapy after extrapleural pneumonectomy for mesothelioma. Prospective analysis of a multi-institutional series

Background and purpose

To evaluate survival, locoregional control and toxicity in a series of 56 mesothelioma patients treated from May 2005 to May 2010 with post-operative radiotherapy after extrapleural pneumonectomy (EPP) in three Italian Institutions (Brescia, Florence, and Modena).

Material and methods

Fifty-six patients treated with adjuvant radiotherapy (RT) after EPP were analyzed. Four patients were treated with 3DCRT, 50 with IMRT and two with helical tomotherapy. Forty-five to 50 Gy in 25 fractions were given to the affected hemithorax and to ipsilateral mediastinum, with a simultaneous integrated boost to the sites of microscopically involved margins up to 60 Gy in 20/56 cases.

Results

Three year locoregional control (LRC), distant metastasis free (DMF), disease free (DF), disease specific (DSS) and overall survival (OS) rates are 90%, 66%, 57%, 62%, and 60%, respectively.

Conclusion

Postoperative RT with modern techniques is an effective method to obtain excellent local control and cure rates in mesothelioma patients submitted to EPP.     

Stereotactic body radiation therapy for lung metastases

Introduction

Stereotactic body radiation therapy (SBRT) has an emerging role in patients affected with pulmonary metastases. Purpose of this study was to evaluate efficacy and tolerability of SBRT in a cohort of patients treated between 2003 and 2009 at our institution.

Methods

A total of 61 patients with oligometastatic lung tumors (single pulmonary nodules in 73.7%) were included in the study. SBRT was performed with a stereotactic body frame and a 3D-conformal technique. Fifty-one patients received 26 Gy in 1 fraction, 22 a dose of 45 Gy in 3 fractions and 3 a dose of 36 Gy in 4 fractions. Primary tumor was lung cancer in 45.7% of patients, colorectal cancer in 21.3% and a variety of other origins in 33%. The primary endpoint was local control, secondary endpoints were survival and toxicity.

Results

After a median follow-up interval of 20.4 months, local control rates at 2 and 3 years were 89% and 83.5%, overall survival 66.5% and 52.5%, cancer-specific survival 75.4% and 67%, progression-free survival 32.4% and 22.3%. Tumor volume was significantly associated to survival, with highest rates in patients with single small tumors. Median survival time was 42.8 months, while median progression-free survival time was 11.9 months. Toxicity profiles were good, with just one case of grade III toxicity (pneumonitis).

Conclusion

This study shows that SBRT is an effective and safe local treatment option for patients with lung metastases. Definitive results are strictly correlated to clinical selection of patients.     

Stereotactic radiotherapy with real-time tumor tracking for non-small cell lung cancer: Clinical outcome

Purpose

To report the clinical outcome of treatment using real-time tumor tracking for 70 patients with inoperable stage I non-small cell lung cancer (NSCLC).

Materials and methods

Seventy inoperable patients with peripherally located early-stage NSCLC were treated with 45 or 60 Gy in three fractions using CyberKnife. Pathology was available in 51% of patients. Thirty-nine patients had a T1-tumor and 31 had a T2-tumor. Markers were placed using the vascular, percutaneous intra-, or extra-pulmonary approach, depending on the risk of pneumothorax.

Results

The actuarial 2-year local control rate for patients treated with 60 Gy was 96%, compared to 78% for patients treated with a total dose of 45 Gy (p = 0.197). All local recurrences (n = 4) occurred in patients with T2-tumors. Overall survival for the whole group at two years was 62% and the cause specific survival was 85%. The median follow-up was 15 months. Grade 3 toxicity occurred in two patients (3%) after marker placement. Treatment-related late grade 3 toxicity occurred in 7 patients (10%). No grade ?4 toxicity occurred.

Conclusion

Excellent local control of 96% at 1- and 2-years was achieved using 60 Gy in three fractions for NSCLC patients treated with the real-time tumor tracking. Toxicity was low.     

Efficacy of a hypofractionated schedule in electron beam radiotherapy for epithelial skin cancer: Analysis of 434 cases

Background and purpose

Efficacy of radiotherapy for epithelial skin cancer was evaluated and treatment outcomes of two electron beam fractionation schedules were compared.

Materials and methods

Outcome data of 434 epithelial skin cancers in 333 patients were analysed; 332 were basal cell carcinomas (BCCs) and 102 squamous cell carcinomas (SCCs). Patients were treated with electron beam, and received either 54 Gy in 18 fractions (n = 159) or 44 Gy in 10 fractions (n = 275). Local recurrence free (LRF) rates were analysed as well as metastases free rates, cancer specific survival (CSS) and cosmetic result.

Results

Median follow-up was 42.8 months. For BCC, actuarial 3-year LRF rates were 97.6% for tumours treated with 54 Gy and 96.9% for 44 Gy. In SCC 3-year LRF rates were 97.0% for 54 Gy and 93.6% for 44 Gy (n.s.).T stage was found to be the only significant factor for recurrence (p = 0.036). Three-year CSS was 98% for SCC and 100% for BCC.

Conclusions

Electron beam irradiation is a safe and effective treatment modality for epithelial skin cancer. In view of a similar efficacy and patient convenience of the hypofractionated schedule, 44 Gy in 10 fractions can be regarded the radiation schedule of choice.     

Helical tomotherapy and intensity modulated proton therapy in the treatment of early stage prostate cancer: A treatment planning comparison

Purpose

To compare helical tomotherapy (HT) and intensity modulated proton therapy (IMPT) on early stage prostate cancer treatments delivered with simultaneous integrated boost (SIB) in moderate hypofractionation.

Material/methods

Eight patients treated with HT were replanned with two-field IMPT (2fIMPT) and five-field IMPT (5fIMPT), using a small pencil beam size (3 mm sigma). The prescribed dose was 74.3 Gy in 28 fractions on PTV1 (prostate) and PTV2 (proximal seminal vesicles), 65.5 Gy on PTV3 (distal seminal vesicles) and on the overlap between rectum and PTVs.

Results

IMPT and HT achieved similar target coverage and dose homogeneity, with 5fIMPT providing the best results. The conformity indexes of IMPT were significantly lower for PTV1+2 and PTV3. Above 65 Gy, HT and IMPT were equivalent in the rectum, while IMPT spared the bladder and the penile bulb from 0 to 70 Gy. From 0 up to 60 Gy, IMPT dosimetric values were (much) lower for all OARs except the femur heads, where HT was better than 2fIMPT in the 25-35 Gy dose range. OARs mean doses were typically reduced by 30-50% by IMPT. NTCPs for the rectum were within 1% between the two techniques, except when the endpoint was stool frequency, where IMPT showed a small (though statistically significant) benefit.

Conclusions

HT and IMPT produce similar dose distributions in the target volume. The current knowledge on dose-effect relations does not allow to quantify the clinical impact of the large sparing of IMPT at medium-to-low doses.     

Managing supraclavicular disease from breast cancer with brachial plexus-sparing techniques using helical tomotherapy

Aims

Managing supraclavicular fossa (SCF) disease in patients with breast cancer can be challenging, with brachial plexopathy recognised as a complication of high-dose radiotherapy to the SCF. Local control of SCF disease is an important end point. Intensity-modulated radiotherapy (IMRT) techniques provide a steep dose gradient and improve the therapeutic index, making it possible to escalate dose to planning target volumes (PTVs), while reducing the dose to organs at risk (OAR). We explored image-guided IMRT techniques using helical tomotherapy to dose escalate SCF lymph nodes with a view to restrict the dose to the brachial plexus.

Materials and methods

Three cases with SCF nodal disease in varying clinical stages of breast cancer were planned and treated using helical tomotherapy-IMRT to assess the feasibility and safety of radiotherapy dose escalation to improve the chances of local control in SCF while restricting the dose to the brachial plexus. Consultant clinical oncologists were asked to define the PTVs and OARs as per agreed inhouse policy. The brachial plexus was outlined as a separate OAR in all three cases. In case 1 the left breast and SCF were treated with adjuvant radiotherapy (40 Gy in 15 fractions) with a sequential boost (10 Gy in five fractions) to the SCF PTV. In case 2, local recurrence was salvaged using a simultaneous integrated boost to the gross tumour plus a 3 mm margin to 63 Gy and 54 Gy to the entire SCF. Case 3 was to control nodal disease with re-irradiation of the SCF to a median dose of 44 Gy, while maintaining a low dose to the brachial plexus. Inverse planning constraints (helical tomotherapy) were applied to the PTV and OARs with the brachial plexus allowed a maximum biologically effective dose (BED) of 120 Gy.

Results

It was possible to treat the SCF to a higher dose using helical tomotherapy-IMRT. The treatment was successful in controlling disease in the SCF. No patients reported symptoms suggestive of brachial plexopathy.

Conclusion

Sequential or simultaneous integrated boost to the SCF was safe and feasible. This is the first publication of dose escalation to the SCF when treating breast cancer with brachial plexus-sparing IMRT techniques. The feasibility of such techniques warrants a multicentre phase II study of dose escalation with IMRT to improve local control in isolated SCF disease.     

Three-dimensional conformal radiation therapy for squamous cell carcinoma of the esophagus: A prospective phase I/II study

Purpose

A prospective phase I-II study was conducted to determine the tolerance and local control rate of three-dimensional conformal radiotherapy (3-DCRT) for esophageal squamous cell carcinoma (SCC).

Methods and materials

Thirty patients underwent 3-DCRT for thoracic esophageal SCC. PTV1 composed of a 1.2-1.5 cm margin lateral around GTV and 3.0 cm margin superior/inferior of GTV. PTV2 encompassed GTV with a margin of 0.5-0.7 cm. The dose for PTV1 was 50 Gy in 2 Gy daily fractions; PTV2 received a boost of 16 Gy in 2 Gy daily fractions to a total dose of 66 Gy.

Results

Median follow-up time was 18 months. The most common acute toxicity was esophagitis in 63% of patients with RTOG grades 1-2, and in 3% with grade 3. RTOG grades 1-2 radiation pneumonitis developed in 27% of patients. One patient developed pulmonary fibrosis RTOG grade 2 and another patient experienced grade 3 pulmonary fibrosis. Two patients developed mild esophageal stricture requiring dilatation. Two-year overall survival, local disease progression-free rate, and distant metastasis-free rate were 69%, 36% and 56%, respectively.

Conclusions

Although 3-DCRT to 66 Gy for esophageal SCC was well tolerated, the local control was disappointing. The result supports the use of chemoradiation as the standard care for esophageal SCC.     

Hypofractionated accelerated CT-guided interstitial Ir-HDR-Brachytherapy as re-irradiation in inoperable recurrent cervical lymphadenopathy from head and neck cancer

Background

Despite significant improvements in the treatment of head and neck cancer (HNC), lymph node recurrences remain a clinical challenge after primary radiotherapy. The value of interstitial (IRT) brachytherapy (BRT) for control of lymph node recurrence remains unclear. In order to clarify its role a retrospective review was undertaken on the value of computed tomography (CT)-guided IRT high-dose-rate (HDR)-BRT in isolated recurrent disease from HNC.

Patients and methods

From 2000 to 2007, 74 patients were treated for inoperable recurrent cervical lymphadenopathy. All patients had previously been treated with radical radiotherapy or chemoradiation with or without surgery. The HDR-BRT delivered a median salvage dose of 30.0 Gy (range, 12.0-36.0 Gy) in twice-daily fractions of 2.0-5.0 Gy in 71 patients and of 30.0 Gy (range, 10.0-36.0 Gy) in once-daily fractions of 6.0-10.0 Gy in three patients.

Results

The overall and disease-free survival rates at one, two and three years were 42%, 19%, 6%, and 42%, 37% and 19%, respectively. The local control probability at one, two and three years was 67% at all three time points. Grade III-IV complications occurred in 13% of patients.

Conclusions

In patients with inoperable recurrent neck disease from HNC, hypofractionated accelerated CT-guided IRT-HDR-BRT can play an important role in providing palliation and tumor control.     

Determining DVH parameters for combined external beam and brachytherapy treatment: 3D biological dose adding for patients with cervical cancer

Purpose

To compare two methods of DVH parameter determination for combined external beam and brachytherapy treatment of cervical cancer.

Materials and methods

Clinical treatment plans from five patients were used in this study. We simulated two applications given with PDR (32 × 60 cGy per application, given hourly) or HDR (4 × 7 Gy in two applications; each application of two fractions of 7 Gy, given within 17 h) standard and optimised treatment plans, all combined with IMRT (25 × 1.8 Gy). Additionally, we simulated an external beam (EBRT) boost to pathological lymph nodes or the parametrium (7 × 2 Gy).We determined D90 of the high-risk CTV (HR-CTV) and D_2cc of bladder and rectum in EQD2 in two ways. (1) ‘Parameter adding’: assuming a uniform contribution of the EBRT dose distribution and adding the values of DVH parameters for the two brachytherapy insertions, and (2) ‘distributions adding’: summing 3D biological dose distributions of IMRT and brachytherapy plans and subsequently determining the values of the DVH parameters. We took α/β = 10 Gy for HR-CTV, α/β = 3 Gy otherwise and half-time of repair 1.5 h.

Results

Without EBRT boost, ‘parameter adding’ yielded a good approximation. With an EBRT boost to lymph nodes, the total D90 HR-CTV was underestimated by 2.6 (SD 1.3)% for PDR and 2.8 (SD 1.4)% for HDR. This was even worse with a parametrium boost: 9.1 (SD 6.2)% for PDR and 9.9 (SD 6.2)% for HDR.

Conclusion

Without an EBRT boost ‘parameter adding’, as proposed by the GEC-ESTRO, yielded accurate results for the values for DVH parameters. If an EBRT boost is given ‘distributions adding’ should be considered.     

Stereotactic body radiotherapy (SBRT) for oligometastatic lung tumors from colorectal cancer and other primary cancers in comparison with primary lung cancer

Purpose

To analyze local control of oligometastatic lung tumors (OLTs) compared with that of primary lung cancer after stereotactic body radiotherapy (SBRT).

Materials and methods

Retrospective record review of patients with OLTs who received SBRT with 50 Gy in 5 fractions. Local control rates (LCRs), toxicities, and factors of prognostic significance were assessed.

Results

Twenty-one colorectal OLTs, 23 OLTs from other origins, and 188 primary lung cancers were included. Multivariate analysis revealed only tumor origin was prognostically significant (p < 0.05). The 1-year/2-year LCRs in colorectal OLTs and OLTs from other origins were 80%/72% and 94%/94%, respectively. The LCR in colorectal OLTs was significantly worse than that in OLTs from the other origins and primary lung cancers with pathological and clinical diagnosis (p < 0.05, p < 0.0001 and p < 0.005). Among 44 OLT patients, Grades 2 and 3 radiation pneumonitis were identified in 2 and 1 patients, respectively. No other toxicities of more than Grade 3 occurred.

Conclusion

SBRT for OLTs is tolerable. The LCR for OLTs from origins other than colorectal cancer is excellent. However, LCR for colorectal OLTs is worse than that from other origins. Therefore dose escalation should be considered to achieve good local control for colorectal OLTs.     

A phase II trial of accelerated hypofractionated three-dimensional conformal radiation therapy in locally advanced non-small cell lung cancer

Purpose

The aim of this study is to evaluate the safety and efficacy of accelerated hypofractionated radiotherapy (HypoRT) combined with sequential chemotherapy in locally advanced non-small cell lung cancer (NSCLC).

Materials and methods

A total of 34 patients with stage III NSCLC were enrolled. All patients received accelerated HypoRT (initially 50 Gy/20 fractions, then a fraction dose of 3 Gy) using three-dimensional conformal radiation therapy (3D-CRT), omitting elective nodal irradiation (ENI), to a total dose of 65-68 Gy. All patients received two cycles of induction chemotherapy; 1-2 cycles of consolidation chemotherapy were given to 31 patients. The primary outcome measure was a profile of radiation toxicity. The secondary endpoints included overall survival (OS), progression-free survival (PFS), locoregional PFS (LR-PFS) and the pattern of initial failure.

Results

Radiation toxicity was minimal. The median and 3-year OS, PFS were 19.0 months, 32.1%; 10.0 months, 29.8%, respectively. The 1-, 2-, and 3-year LR-PFS were 69.6%, 60.9% and 60.9%, respectively. No patient experienced isolated elective nodal failure as the first site of failure.

Conclusion

This study suggests that accelerated HypoRT using 3D-CRT omitting ENI can be used in combination with sequential chemotherapy in locally advanced NSCLC.     

Stereotactic radiotherapy of histologically proven inoperable stage I non-small cell lung cancer: Patterns of failure

Background and purpose

To report patterns of failure of stereotactic body radiation therapy (SBRT) in inoperable patients with histologically confirmed stage I NSCLC.

Materials and methods

Ninety-two inoperable patients (median age: 75 years) with clinically staged, histologically proven T1 (n = 31) or T2 (n = 61), N0, M0 non-small cell lung cancer (NSCLC) were included in this study. Treatment consisted of 3-5 fractions with 7-15 Gy per fraction prescribed to the 60% isodose.

Results

Freedom from local recurrence at 1, 3 and 5 years was 89%, 83% and 83%, respectively. All 10 local failures were observed in patients with T2 tumors. Isolated regional recurrence was observed in 7.6%. The crude rate of distant progression was 20.7%. Overall survival at 1, 3, and 5 years was 79%, 38% and 17% with a median survival of 29 months. Disease specific survival at 1, 3, and 5 years was 93%, 64% and 48%. Karnofsky performance status, T stage, gross tumor volume and tumor location had no significant impact on overall and disease specific survival. SBRT was generally well tolerated and all patients completed therapy as planned.

Conclusion

SBRT for stage I lung cancer is very well tolerated in this patient cohort with significant cardiopulmonal comorbidity and results in excellent local control rates, although a considerable portion develops regional and distant metastases.     

Impact of radiation dose on locoregional control and survival on squamous cell carcinoma of anal canal

Purpose

To perform a systematic analysis of clinical data of presentation, treatment, outcome, toxicity, survival and other associated prognostic factors of the patients of anal canal who received treatment at our hospital.

Methods and materials

The medical records of 257 patients treated with radiotherapy with or without chemotherapy from the year 1985 to 2005 were studied.

Results

Median follow-up was 36 months. Complete clinical response after radiotherapy was 74.4% in the whole group. The 5 years overall (OAS) and disease-free (DFS) survival for the whole group was 71.5% and 61%, respectively. Patients with T1-2 tumors which received the radiation dose between 55 and 60 Gy had superior locoregional control, DFS and OAS. Similarly T3-4 tumors receiving radiation dose more than 60 Gy independently improved the locoregional control, DFS and OAS irrespective of the nodal status and addition of chemotherapy.

Conclusions

Radiation dose of 56-60 Gy for T1 and T2 and 65 Gy for T3 and T4 tumors along with concurrent chemotherapy is required to achieve better local control, disease-free survival and overall survival, with acceptable toxicity.     

Is single fraction 15 Gy the preferred high dose-rate brachytherapy boost dose for prostate cancer?

Background and purpose

High dose-rate (HDR) brachytherapy is most commonly administered as a boost in two or more fractions combined with external beam radiotherapy (EBRT). Our purpose is to compare outcomes with a single fraction HDR boost to that with a standard fractionated boost in intermediate risk prostate cancer.

Materials and methods

Results of two sequential phase II clinical trials are compared. The Single Fraction protocol consists of 15 Gy HDR in one fraction followed by 37.5 Gy EBRT in 15 fractions over 3 weeks; the Standard Fractionation protocol consisted of two HDR fractions each of 10 Gy, 1 week apart, followed by 45 Gy EBRT in 25 fractions. Patients had intermediate risk disease, and were well balanced for prognostic factors. Patients were followed prospectively for efficacy, toxicity and health-related quality of life (Expanded Prostate Index Composite). Efficacy was assessed biochemically using the Phoenix definition, and by biopsy at 2 years.

Results

The Single Fraction protocol accrued 123 patients and the Standard Fractionation protocol, 60. With a median follow-up of 45 and 72 months, respectively, the biochemical disease-free survival was 95.1% and 97.9% in the Single and Standard Fractionation trials (p = 0.3528). Two-year prostate biopsy was positive in only 4% and 8%, respectively. There was no difference in late urinary or rectal toxicity rates, or in health-related quality of life between the two protocols.

Conclusions

The Single Fraction HDR protocol results in high disease control rate and low toxicity similar to our previous protocol using two HDR insertions, with significant savings in resources. While mature results with longer follow-up are awaited, a single 15 Gy may be considered as a standard fractionation regimen in combination with EBRT for men with intermediate risk disease.     

Reduced dose radiotherapy for local control in non-Hodgkin lymphoma: A randomised phase III trial

Purpose

This multicentre, prospective, randomised-controlled trial compared efficacy and toxicity of differing radiotherapy doses in non-Hodgkin lymphoma (NHL).

Patients and methods

Patients with any histological subtype of NHL, requiring radiotherapy for local disease control, whether radical, consolidative or palliative, were included. Three hundred and sixty one sites of indolent NHL (predominantly follicular NHL and marginal zone lymphoma) were randomised to receive 40-45 Gy in 20-23 fractions or 24 Gy in 12 fractions. Six hundred and forty sites of aggressive NHL (predominantly diffuse large B cell lymphoma as part of combined-modality therapy) were randomised to receive 40-45 Gy in 20-23 fractions or 30 Gy in 15 fractions. Patients with all stages of disease, having first-line and subsequent therapies were included; first presentations of early-stage disease predominated.

Results

There was no difference in overall response rate (ORR) between standard and lower-dose arms. In the indolent group, ORR was 93% and 92%, respectively, (p = 0.72); in the aggressive group, ORR was 91% in both arms (p = 0.87). With a median follow-up of 5.6 years, there was no significant difference detected in the rate of within-radiation field progression (HR = 1.09, 95%CI = 0.76-1.56, p = 0.64 in the indolent group; HR = 0.98, 95%CI = 0.68-1.4, p = 0.89 in the aggressive group). There was also no significant difference detected in the progression free or overall survival. There was a trend for reduced toxicities in the low-dose arms; only the reduction in reported erythema reached significance.

Conclusion

In a large, randomised trial, there was no loss of efficacy associated with radiotherapy doses of 24 Gy in indolent NHL and 30 Gy in aggressive NHL, compared with previous standard doses of 40-45 Gy.     

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

Background and purpose

Fractionated 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.

Materials and methods

Data 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.

Results

Compared 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.

Conclusions

Inter-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.     

A comparison of several modulated radiotherapy techniques for head and neck cancer and dosimetric validation of VMAT

Purpose

Volumetric modulated arc therapy (VMAT) has the potential to shorten treatment times for fluence modulated radiotherapy. We compared dose distributions of VMAT, step-and-shoot IMRT and serial tomotherapy for typical head and neck (H&N) planning target volumes (PTV) with sparing of one parotid, a complex paradigm and a situation often encountered in H&N radiotherapy. Finally, we validated the dosimetric accuracy of VMAT delivery.

Material and methods

Based on CT datasets of 10 patients treated for H&N cancer (PTV1:60 Gy/PTV2:56 Gy) with IMRT (7/9 fields), serial tomotherapy (MIMiC) and VMAT were compared with regard to plan quality and treatment efficiency. Plan quality was assessed by calculating homogeneity/conformity index (HI/CI), mean dose to parotid and brain stem and the maximum dose to the spinal cord. For plan efficiency evaluation, total treatment time (TTT) and number of monitor units (MU) were considered. A dosimetric evaluation of VMAT was performed using radiosensitive film, ion chamber and 2D-array.

Results

For MIMiC/IMRT_7F/IMRT_9F/VMAT, mean CI was 1.98/2.23/2.23/1.82, HI_PTV1 was 1.12/1.20/1.20/1.11 and HI_PTV2 was 1.11/1.15/1.13/1.12. Mean doses to the shielded parotid were 19.5 Gy/14.1 Gy/13.9 Gy/14.9 Gy and the spinal cord received maximum doses of 43.6 Gy/40.8 Gy/41.6 Gy/42.6 Gy. The mean MU’s were 2551/945/925/521 and the mean TTT was 12.8 min/7.6 min/8.5 min/4.32 min. The ion chamber measurements showed an absolute deviation of 0.08 ± 1.10% and 98.45 ± 3.25% pixels passed γ-analyses for 3%/3 mm and 99.95 ± 0.09% for 5%/5 mm for films. 2D-array measurements reported an agreement for 3%/3 mm of 95.65 ± 2.47%-98.33 ± 0.65% and for 5%/5 mm 99.79 ± 0.24%-99.92 ± 0.09% depending on the measurement protocol.

Conclusion

All treatment paradigms produced plans of excellent quality and dosimetric accuracy with IMRT providing best OAR sparing and VMAT being the most efficient treatment option in our comparison of treatment plans with high complexity.     

Volumetric modulated arc therapy (VMAT) vs. serial tomotherapy, step-and-shoot IMRT and 3D-conformal RT for treatment of prostate cancer

Introduction

Volumetric modulated arc therapy (VMAT), a complex treatment strategy for intensity-modulated radiation therapy, may increase treatment efficiency and has recently been established clinically. This analysis compares VMAT against established IMRT and 3D-conformal radiation therapy (3D-CRT) delivery techniques.

Methods

Based on CT datasets of 9 patients treated for prostate cancer step-and-shoot IMRT, serial tomotherapy (MIMiC), 3D-CRT and VMAT were compared with regard to plan quality and treatment efficiency. Two VMAT approaches (one rotation (VMAT1x) and one rotation plus a second 200° rotation (VMAT2x)) were calculated for the plan comparison. Plan quality was assessed by calculating homogeneity and conformity index (HI and CI), dose to normal tissue (non-target) and D_95% (dose encompassing 95% of the target volume). For plan efficiency evaluation, treatment time and number of monitor units (MU) were considered.

Results

For MIMiC/IMRT_MLC/VMAT2x/VMAT1x/3D-CRT, mean CI was 1.5/1.23/1.45/1.51/1.46 and HI was 1.19/1.1/1.09/1.11/1.04. For a prescribed dose of 76 Gy, mean doses to organs-at-risk (OAR) were 50.69 Gy/53.99 Gy/60.29 Gy/61.59 Gy/66.33 Gy for the anterior half of the rectum and 31.85 Gy/34.89 Gy/38.75 Gy/38.57 Gy/55.43 Gy for the posterior rectum. Volumes of non-target normal tissue receiving ?70% of prescribed dose (53 Gy) were 337 ml/284 ml/482 ml/505 ml/414 ml, for ? 50% (38 Gy) 869 ml/933 ml/1155 ml/1231 ml/1993 ml and for ? 30% (23 Gy) 2819 ml/3414 ml/3340 ml/3438 ml /3061 ml. D_95% was 69.79 Gy/70.51 Gy/71,7 Gy/71.59 Gy/73.42 Gy. Mean treatment time was 12 min/6 min/3.7 min/1.8 min/2.5 min.

Conclusion

All approaches yield treatment plans of improved quality when compared to 3D-conformal treatments, with serial tomotherapy providing best OAR sparing and VMAT being the most efficient treatment option in our comparison. Plans which were calculated with 3D-CRT provided good target coverage but resulted in higher dose to the rectum.