Helical Tomotherapy as a Means of Delivering Accelerated Partial Breast Irradiation

Is stereotactic CyberKnife radiotherapy or multicatheter HDR brachytherapy the better option dosimetrically for accelerated partial breast irradiation?

OBJECTIVE

To compare dosimetrically the stereotactic CyberKnife (CK) therapy and multicatheter high-dose-rate (HDR) brachytherapy (BT) for accelerated partial breast irradiation (APBI).

METHODS

Treatment plans of 25 patients treated with CK were selected, and additional plans using multicatheter HDR BT were created on the same CT images. The prescribed dose was 6.25/25 Gy in both plans to the target volume (PTV). The dose-volume parameters were calculated for both techniques and compared.

RESULTS

The D90 total dose of the PTV was significantly lower with CK than with HDR BT, D90 was 25.7 Gy, and 27.0 Gy (p < 0.001). However, CK plans were more conformal than BT, COIN was 0.87, and 0.81 (p = 0.0030). The V50 of the non-target breast was higher with CK than with BT: 10.5% and 3.3% (p = 0.0010), while there was no difference in the dose of the contralateral breast and contralateral lung. Dose to skin, ipsilateral lung, and ribs were higher with CK than with BT: D₁ was 20.6 Gy vs. 11.5 Gy (p = 0.0018) to skin, 11.4 Gy vs. 9.6 Gy (p = 0.0272) to ipsilateral lung and 18.5 Gy vs. 12.3 Gy (p = 0.0013) to ribs, while D_0.1 to heart was lower, 3.0 Gy vs. 3.2 Gy (p = 0.0476), respectively.

CONCLUSIONS

Multicatheter HDR BT yields more advantageous plans than stereotactic CyberKnife treatment in accelerated partial breast irradiation, except in terms of dose conformality and the dose to the heart. There was no difference in the dose of the contralateral breast and lung.

Detection of a numeric value predictive of increased dose to left anterior descending coronary artery (LAD) in radiotherapy of breast cancer

Purpose

We have evaluated thoracic conformation of patients in order to derive a numeric value predictive of an increased dose to left anterior descending coronary artery (LAD), critical structure for the development of late radio induced cardiac morbidity.

Methods

We have evaluated 91 patients (36–88 years) affected by breast cancer stage I–II (Tis–T1–2 N0–1), undergoing adjuvant radiotherapy with conventional fractionation. For each patient on CT images was measured the distance between the back face of the sternum (manubrium) and the anterior face of body of the corresponding vertebra (a), and the distance measured on the line at 45° between the vertebral body of the same vertebra and the back face of the rib corresponding (b). The a/b ratio showed values between 0.626 and 1.123. We used the median value (0.821) as cut-off to divide the patients in two groups. We calculated in both groups: Volume (Vol) heart, Vol LAD with an expansion of 0.6 mm; Dmean LAD (Gy); Dmax LAD (Gy); V10–V20–V30 (%) LAD and we correlated these values with parametric and non-parametric tests.

Results

The Pearson test has showed a statistically significant correlation between Vol breast and V10, V20, V30 with borderline significance (p = 0.006; p = 0.02; p = 0.05). The data were confirmed by testing non-parametric Kendall (tau = 0.004; tau = 0.015; tau = 0.016) and Spearman (rho = 0.003; rho = 0.016; rho = 0.015). We conducted categorizing into quartiles of breast volume and evaluated the correlation with a/b. We have found a significative correlation (p = 0.01) between small Vol breast (≤660.23 cc) and a/b < 0.0821 and greater Vol breast (>660.23 cc) with a/b > 0.0821. From the evaluation of the distribution of V10 in the two groups taking account of the Dmean ≤5 or >5 significance was found with a/b; Chi square 0.009 (0.01). Values ≤5 were observed in women with a/b < 0.0821. Values >5 in women with a/b > 0.0821.

Conclusions

The geometric conformity of chest thorax considering a/b and the value of 0.0821 can reveals an important parameter in the selection of patients suitable for radiation therapy on left breast in order to evaluate the risk of late cardiac events. This consideration during treatment planning can change the technique or the set-up allowing the development of a customized plan.

Initial validation and clinical experience with 3D optical-surface-guided whole breast irradiation of breast cancer

We had introduced 3D optical surface-guided radiotherapy (SGRT) of the breast cancer (BC). We then initiated the feasibility, accuracy, and precision studies of stereovision in detection of any breast displacement through the course of treatment for total thirty breasts undertaken whole breast irradiation (WBI). In the SGRT, CT-based plan data were parsed into an in-house computer program through which the reference surfaces were generated in 3D video format. When patients were positioned on treatment Tables, real-time stereovisions were rapidly acquired while the live surface tracking shown steady thorax motion. The real-time surface images were automatically aligned with the reference surface and detected shape and location changes of the breast were online corrected through the Table and beam adjustments. Accumulated dose to each patient was computed according to the frequency distribution of the measured breast locations during beam on time. Application of SGRT had diminished large skin-marking errors of > 5-mm and daily breast-setup errors of >10-mm that occurred on half of cases. Accuracy (mean) and precision (two standard deviations) of the breast displacements across the tangential field edges in the (U, V) directions were improved from (-0.5 ± 8.8,  2.2 ± 10.8) mm in conventional setup to (0.4 ± 4.6,  0.7 ± 4.4) mm in the final position while intra-fractional motion contributed only (0.1 ± 2.8, 0.0 ± 2.2) mm in free breathing. Dose uniformity and coverage to targets had both been increased by up to 10% and the lung or heart intersections have been decreased by half of those volumes if they were irradiated at the initial positions. SGRT of BC appears to be feasible regardless of skin tones, as fast as a snapshot for 3D imaging, and very accurate and precise for daily setup of flexible breast targets. Importantly, the technique allows us to verify the breast shape and position during beam-on time.

[Conformal accelerated partial breast irradiation: state of the art]

Breast conserving treatment (breast conserving surgery followed by whole breast irradiation) has commonly been used in early breast cancer since many years. New radiation modalities have been recently developed in early breast cancers, particularly accelerated partial breast irradiation. Three-dimensional conformal accelerated partial breast irradiation is the most commonly used modality of radiotherapy. Other techniques are currently being developed, such as intensity-modulated radiotherapy, arctherapy, and tomotherapy. The present article reviews the indications, treatment modalities and side effects of accelerated partial breast irradiation.

Simultaneous irradiation of the breast and regional lymph nodes in prone position using helical tomotherapy

OBJECTIVE

We investigated dosimetric advantages of using helical tomotherapy to simultaneously irradiate the breast and regional lymph nodes for patients positioned prone, and compared tomotherapy plan qualities for the prone position with those previously published for the supine position.

METHODS

Tomotherapy plans for 11 patients (5 left breast, 6 right) simulated with the involved breast suspended downward were generated. Each target (ipsilateral breast and supraclavicular, axillary and internal mammary chain nodes) was to receive 45 Gy.

RESULTS

For targets, V(40.5)≥99.9% and V(42.8)≥99.5% for all patients, where V(40.5) and V(42.8) denote the relative target volume receiving at least 40.5 and 42.8 Gy, respectively. The targets' maximum dose was, on average, approximately 49.5 Gy. The mean doses to the contralateral lung and heart were lower for right-breast cases (2.8 Gy lung, 2.7 Gy heart) than for left-breast cases (3.8 Gy lung, 8.7 Gy heart). Mean organ doses to the ipsilateral lung (9.3 Gy) and contralateral breast (2.3 Gy) from the prone breast tomotherapy plans were similar to those reported for conventional radiotherapy techniques. For the left breast with regional nodes, tomotherapy plans for prone-positioned patients yielded lower mean doses to the contralateral breast and heart than previously reported data for tomotherapy plans for supine-positioned patients.

CONCLUSION

Helical tomotherapy with prone breast positioning can simultaneously cover the breast and regional nodes with acceptable uniformity and can provide reduced mean dose to proximal organs at risk compared with tomotherapy with supine position. The similarity of plan quality to existing data for conventional breast radiotherapy indicates that this planning approach is appropriate, and that the risk of secondary tumour formation should not be significantly greater.

Three-dimensional patient setup errors at different treatment sites measured by the Tomotherapy megavoltage CT

BACKGROUND AND PURPOSE

Reduction of interfraction setup uncertainty is vital for assuring the accuracy of conformal radiotherapy. We report a systematic study of setup error to assess patients' three-dimensional (3D) localization at various treatment sites.

PATIENTS AND METHODS

Tomotherapy megavoltage CT (MVCT) images were scanned daily in 259 patients from 2005-2008. We analyzed 6,465 MVCT images to measure setup error for head and neck (H&N), chest/thorax, abdomen, prostate, legs, and total marrow irradiation (TMI). Statistical comparisons of the absolute displacements across sites and time were performed in rotation (R), lateral (x), craniocaudal (y), and vertical (z) directions.

RESULTS

The global systematic errors were measured to be less than 3 mm in each direction with increasing order of errors for different sites: H&N, prostate, chest, pelvis, spine, legs, and TMI. The differences in displacements in the x, y, and z directions, and 3D average displacement between treatment sites were significant (p < 0.01). Overall improvement in patient localization with time (after 3-4 treatment fractions) was observed. Large displacement (> 5 mm) was observed in the 75(th) percentile of the patient groups for chest, pelvis, legs, and spine in the x and y direction in the second week of the treatment.

CONCLUSION

MVCT imaging is essential for determining 3D setup error and to reduce uncertainty in localization at all anatomical locations. Setup error evaluation should be performed daily for all treatment regions, preferably for all treatment fractions.

Dosimetric and clinical review of helical tomotherapy

As a modality for delivering rotational therapy, helical tomotherapy offers dosimetric advantages by combining a continuously rotating gantry with a binary multileaf collimator. Helical tomotherapy, embodied in the TomoTherapy(®) Hi-Art II(®) system, delivers intensity-modulated fan beams in a helical pattern using binary multileaf collimator leaves while the couch is translated through the gantry. Helical tomotherapy offers the possibility of treating a variety of cases--from simple to complex--with improved target conformality and sensitive structure sparing compared with 3D or conventional static field IMRT plans, thereby allowing biologically effective dose escalation. For precise irradiation and possible treatment adaptation, the fully integrated on-board image-guidance system provides online volumetric images of patient anatomy using 3.5-MV x-ray beams and the xenon computed tomography detector. Several review articles were published before the year 2007 but emphasized the technical aspects of helical tomotherapy. In this article, we review very recent papers and focus on the dosimetric and clinical aspects of helical tomotherapy.

Helical tomotherapy in patients with breast cancer and complex treatment volumes

PURPOSE

To describe early clinical results of tomotherapy treatment in patients with breast cancer and complex treatment volumes.

METHODS AND MATERIALS

Ten patients were treated with tomotherapy between January 2009 and March 2010. Treatment planning objectives were to cover at least 95% of the planning target volume with the 95% isodose; to have a minimum dose of 90% and a maximum dose of 105%. All treatments included daily CT/megavoltage image guidance. Acute toxicity was recorded weekly.

RESULTS

Six patients were treated because constraints were not accomplished for heart, lung or contralateral breast in a previous three-dimensional conformal plan; two for preexisting cardiac or pulmonary disease, and two more for bilateral breast irradiation. Treatment volumes included the whole breast in the majority of patients, as well as the supraclavicular and the internal mammary chain nodes when indicated. Most patients were older than 50 years, and had an early breast cancer, with positive oestrogen receptors, negative HER2 expression and a poorly differentiated, infiltrating ductal carcinoma. The majority of patients had received neoadjuvant chemotherapy associated to breast-conserving surgery and adjuvant hormonotherapy. Median homogeneity index was 1.09; median coverage index was 0.81. Median V20Gy and V10Gy for ipsilateral lung was 20% and 37.1% respectively. Median V25 and V35 for heart was 15% and 4% respectively. Median dose for contralateral breast was 7 Gy. Skin acute toxicity was grade 1 in 41.7% and grade 2 in 58.3%.

CONCLUSION

Tomotherapy is a technique capable of delivering a well tolerated treatment with high homogeneity and coverage indexes and high capabilities for sparing the organs at risk in patients with anatomically complex breast cancer, bilateral breast cancer, indication for internal mammary chain node irradiation, cardiac toxicity derived from chemotherapy, or preexisting cardiac or pulmonary disease. Further studies are required to evaluate local control and late toxicity.

The role of helical tomotherapy in the treatment of bone plasmacytoma

We evaluated the early clinical outcome of patients with solitary bone plasmacytoma (SP) or a solitary lesion of multiple myeloma (MM) treated with helical tomotherapy (HT) compared with 3D conformal radiotherapy (3D-CRT), in terms of target coverage and exposure of critical organs. Ten patients with SP and 3 patients with a solitary lesion of MM underwent radiation therapy (RT) delivered by HT, to a dose of 40 Gy in 20 fractions. Treatment planning was then performed with 3D-CRT and the dosimetric parameters of both techniques were compared. Patients were also assessed for response to treatment and acute toxicities. With a median follow-up of 13 months, 78% of patients with pain before RT had resolution of their symptoms. Coverage of target lesion was adequate with both techniques in 12 of 13 patients. Target coverage was significantly lower for HT (V(95%) = 98.55% vs. 97.15%; p = 0.04, for 3D-CRT and HT, respectively). Target overdoses were also lower with HT (V(105%) = 2.01% vs. 0.19%; p= 0.16), although nonsignificant. Finally, there were no significant differences in organs-at-risk irradiation between both techniques. The early treatment tolerance was excellent, with no toxicity higher than grade I. RT of SP and MM with a solitary lesion can be safely delivered with HT, with no major acute side effects and good symptomatic control. Finally, HT provides a dosimetry similar to that of 3D-CRT in terms of organs-at-risk sparing and target volume coverage.

Feasibility of intrafraction whole-body motion tracking for total marrow irradiation

With image-guided tomotherapy, highly targeted total marrow irradiation (TMI) has become a feasible alternative to conventional total body irradiation. The uncertainties in patient localization and intrafraction motion of the whole body during hour-long TMI treatment may pose a risk to the safety and accuracy of targeted radiation treatment. The feasibility of near-infrared markers and optical tracking system (OTS) is accessed along with a megavoltage scanning system of tomotherapy. Three near-infrared markers placed on the face of a rando phantom are used to evaluate the capability of OTS in measuring changes in the markers' positions as the rando is moved in the translational direction. The OTS is also employed to determine breathing motion related changes in the position of 16 markers placed on the chest surface of human volunteers. The maximum uncertainty in locating marker position with the OTS is 1.5 mm. In the case of normal and deep breathing motion, the maximum marker position change is observed in anterior-posterior direction with the respective values of 4 and 12 mm. The OTS is able to measure surface changes due to breathing motion. The OTS may be optimized to monitor whole body motion during TMI to increase the accuracy of treatment delivery and reduce the radiation dose to the lungs.

Simultaneous integrated boost in breast conserving treatment of breast cancer: a dosimetric comparison of helical tomotherapy and three-dimensional conformal radiotherapy

BACKGROUND AND PURPOSE

To evaluate the dosimetry of helical tomotherapy (HT) and three-dimensional conformal radiotherapy (3D-CRT) in breast cancer patients undergoing whole breast radiation with simultaneous integrated boost (SIB) of the tumor bed.

MATERIAL AND METHODS

Thirteen patients with breast cancer treated by lumpectomy and requiring whole breast radiotherapy with tumor bed boost were planned using both HT and 3D-CRT using the field-in-field technique. The whole breast and tumor bed were prescribed 50.68 Gy and 64.4 Gy, respectively, in 28 fractions. Dosimetries for both techniques were compared.

RESULTS

Coverage of the whole breast was adequate with both techniques (V(95%)=96.22% vs. 96.25%, with HT and 3D-CRT, respectively; p=0.64). Adequate tumor bed coverage was also achieved, although it was significantly lower with HT (V(95%)=97.18% vs. 99.72%; p<0.001). Overdose of the breast volume outside the tumor bed was significantly lower with HT (V(54.23 Gy)=12.47% vs. 30.83%; p<0.001). Ipsilateral lung V(20 Gy) (6.34% vs. 10.17%; p<0.001), V(5 Gy) (16.54% vs. 18.53%; p<0.05) and mean dose (4.05 Gy vs. 6.36 Gy; p<0.001) were significantly lower with HT. In patients with left-sided tumors, heart V(30 Gy) (0.03% vs. 1.14%; p<0.05) and mean dose (1.35 Gy vs. 2.22 Gy; p<0.01) were significantly lower with HT, but not V(5 Gy). Contralateral breast V(5 Gy) (0.27% vs. 0.00%; p<0.01) and maximum dose were significantly increased with HT.

CONCLUSIONS

In breast cancer treated with SIB, both HT and 3D-CRT provided adequate target volume coverage and low heart doses. Tumor bed coverage was slightly lower with HT, but HT avoided unnecessary breast overdosage while improving ipsilateral lung dosimetry.

Multimodality image guided total marrow irradiation and verification of the dose delivered to the lung, PTV, and thoracic bone in a patient: a case study

This work reports our initial experience using multimodality image guidance to improve total marrow irradiation (TMI) using helical tomotherapy. We also monitored the details of the treatment delivery to glean information necessary for the implementation of future adaptive processes. A patient with metastatic Ewing's sarcoma underwent MRI, and bone scan imaging prior to TMI. A whole body kilovoltage CT (kVCT) scan was obtained for intensity modulated TMI treatment planning, including a boost treatment to areas of bony involvement. The delivered dose was estimated by using MVCT images from the helical tomotherapy treatment unit, compared to the expected dose distributions mapped onto the kVCT images. Clinical concerns regarding patient treatment and dosimetric uncertainties were also evaluated. A small fraction of thoracic bone volume received lower radiation dose than the prescribed dose. Reconstructed planned treatment volume (PTV) and the dose delivered to the lung were identical to planned dose. Bone scan imaging had a higher sensitivity for detecting skeletal metastasis compared to MR imaging. However the bone scan lacked sufficient specificity in three dimensions to be useful for planning conformal radiation boost treatments. Inclusion of appropriate imaging modalities improves detection of metastases, which allows the possibility of a radiation dose boost to metastases during TMI. Conformal intensity modulated radiation therapy via helical tomotherapy permitted radiation delivery to metastases in the skull with reduced dose to brain in conjunction with TMI. While TMI reduces irradiation to the lungs, onboard megavoltage computed tomography (MVCT) to verify accurate volumetric dose coverage to marrow-containing thoracic bones may be essential for successful conformal TMI treatment.

Hypofractionated Breast and Chest Wall Irradiation Using Simultaneous in-field Boost IMRT Delivered via Helical Tomotherapy

Although helical tomotherapy has been described as a means of administering accelerated partial breast irradiation, its practicality in routine whole breast irradiation as part of breast conserving therapy or chest wall irradiation has been questioned. In this technical note we describe our method of whole breast or chest wall irradiation using helical tomotherapy based image-guided, hypofractionated, simultaneous in-field boost intensity modulated radiation therapy.

We have observed that excellent dose-distributions can be achieved with helical tomotherapy through a careful selection of treatment planning parameters. Dose homogeneity to the whole breast and simultaneously targeted lumpectomy region appears superior to conventional “tangents” with minimal hot or cold spots. Dose-volume histogram analysis documents effective reduction of high dose to critical sensitive structures (heart and lung) although a greater volume of these non-target organs receives low dose compared to what is typical with tangential beams. Treatment planning is efficient and is usually completed within one to two hours, although physician contouring requires more time and attention than non-IMRT approaches. Pretreatment megavoltage CT (MVCT) imaging has proved invaluable in aiding set-up and engenders greater confidence that the planned IMRT dose distributions are truly being delivered. In some situations, MVCT can provide visual feedback when a seroma or overall breast volume has changed significantly since simulation, thereby identifying cases where replanning might be prudent. Treatment is brief, typically completed in 6 to 9 minutes.

Initial clinical application has confirmed the feasibility and practicality of helical tomotherapy as an efficient means of administering radiation therapy for routine breast-conserving therapy and post-mastectomy chest wall irradiation. A simultaneous in-field boost technique reduces the length of the overall course by about a week thereby adding convenience and reducing costs. Further refinements of our technique are being explored and formal prospective clinical evaluation is underway.

Evaluating target coverage and normal tissue sparing in the adjuvant radiotherapy of malignant pleural mesothelioma: helical tomotherapy compared with step-and-shoot IMRT

PURPOSE

To evaluate the potential of helical tomotherapy in the adjuvant treatment of malignant pleural mesothelioma and compare target homogeneity, conformity and normal tissue dose with step-and-shoot intensity-modulated radiotherapy.

METHODS AND MATERIALS

Ten patients with malignant pleural mesothelioma who had undergone neoadjuvant chemotherapy with cisplatin and permetrexed followed by extrapleural pneumonectomy (EPP) were treated in our department with 54 Gy to the hemithorax delivered by step-and-shoot IMRT. A planning comparison was performed by creating radiation plans for helical tomotherapy. The different plans were compared by analysing target homogeneity using the homogeneity indices HI(max) and HI(min) and target conformity by using the conformity index CI(95). To assess target coverage and normal tissue sparing TV(90), TV(95) and mean and maximum doses were compared.

RESULTS

Both modalities achieved excellent dose distributions while sparing organs at risk. Target coverage and homogeneity could be increased significantly with helical tomotherapy compared with step-and-shoot IMRT. Mean dose to the contralateral lung could be lowered beyond 5 Gy.

CONCLUSIONS

Our planning study showed that helical tomotherapy is an excellent option for the adjuvant intensity-modulated radiotherapy of MPM. It is capable of improving target coverage and homogeneity.

Cardiac toxicity in breast cancer survivors: review of potential cardiac problems

As breast cancer survival is increased by the diagnosis of earlier-stage disease and treatments improve, the side effects of cancer treatments, such as cardiotoxicity, remain clinically important. Although physicians have known for 30 years that anthracyclines cause acute and chronic cardiotoxicity, the cardiotoxic effects of radiation therapy, hormonal therapy (including tamoxifen and the aromatase inhibitors), and chemotherapy with taxanes and trastuzumab treatment have emerged more recently. This review examines the cardiac toxicity of adjuvant therapy, monitoring for early changes and existing guidelines for monitoring cardiac function in patients with breast cancer.

Skin-sparing radiation using intensity-modulated radiotherapy after conservative surgery in early-stage breast cancer: a planning study

PURPOSE

To evaluate the feasibility of skin-sparing by configuring it as an organ-at-risk (OAR) while delivering whole-breast intensity-modulated radiotherapy (IMRT) in early breast cancer.

METHODS AND MATERIALS

Archival computed tomography scan images of 14 left-sided early-breast tumor patients who had undergone lumpectomy were selected for this study. Skin was contoured as a 4- to 5-mm strip extending from the patient outline to anterior margin of the breast planning target volume (PTV). Two IMRT plans were generated by the helical tomotherapy approach to deliver 50 Gy in 25 fractions to the breast alone: one with skin dose constraints (skin-sparing plan) and the other without (non-skin-sparing plan). Comparison of the plans was done using a two-sided paired Student t test.

RESULTS

The mean skin dose and volume of skin receiving 50 Gy were significantly less with the skin-sparing plan compared with non-skin-sparing plan (42.3 Gy vs. 47.7 Gy and 12.2% vs. 57.8% respectively; p < 0.001). The reduction in skin dose was confirmed by TLD measurements in anthropomorphic phantom using the same plans. Dose-volume analyses for other OARs were similar in both plans.

CONCLUSIONS

By configuring the skin as an OAR, it is possible to achieve skin dose reduction while delivering whole-breast IMRT without compromising dose profiles to PTV and OARs.

A Dosimetric Comparison of Electronic Compensation, Conventional Intensity Modulated Radiotherapy, and Tomotherapy in Patients With Early-Stage Carcinoma of the Left Breast

PURPOSE

Intensity modulated radiation therapy (IMRT) has been shown to significantly reduce dose to normal tissue while maintaining coverage of the clinical target volume (CTV) in patients with intact breast cancer. We compared delivery of whole breast irradiation utilizing three techniques: electronic tissue compensation (ECOMP), inverse-planned dynamic multileaf collimation IMRT (DMLC), and tomotherapy (TOMO).

PATIENTS AND METHODS

Ten patients with early stage, left-sided breast cancer were selected for planning. CTV was defined as breast encompassed in a standard tangent field minus the superficial 5 mm from the skin edge. Normal tissue contours included the heart, lungs, and contralateral breast. Plans included delivery of 45 Gy in 25 fractions and were normalized to ensure > or =95% coverage of the CTV. Isodose distributions and dose-volume histograms for CTV and normal tissue were compared between plans. The time it took to plan each patient excluding contouring, as well as number of monitor units (MUs) required to execute each plan were additionally tabulated.

RESULTS

The TOMO plans resulted in significantly greater heterogeneity (CTV V(115)) versus ECOMP (p = 0.0029). The ECOMP plans resulted in significantly lower doses to heart, lung, and contralateral breast when compared with TOMO plans. The ECOMP plans were generated in the shortest time (12 min) and resulted in the lowest number of MUs when compared with DMLC (p = 0.002, p < 0.0001) and TOMO (p = 0.0015, p < 0.0001).

CONCLUSIONS

The ECOMP plans produced superior dose distributions in both the CTV and normal tissue when compared with TOMO or DMLC plans. In addition, ECOMP plans resulted in the lowest number of MUs and labor cost.

Distribution of Brain Metastases in Relation to the Hippocampus: Implications for Neurocognitive Functional Preservation

PURPOSE

With the advent of intensity-modulated radiotherapy, the ability to limit the radiation dose to normal tissue offers an avenue to limit side effects. This study attempted to delineate the distribution of brain metastases with relation to the hippocampus for the purpose of exploring the viability of tomotherapy-guided hippocampal sparing therapy potentially to reduce neurocognitive deficits from radiation.

METHODS AND MATERIALS

The pre-radiotherapy T1-weighted, postcontrast axial MR images of 100 patients who received whole brain radiotherapy, stereotactic radiosurgery, or a radiosurgical boost following whole brain radiotherapy between 2002 and 2006 were examined. We contoured brain metastases as well as hippocampi with 5-, 10-, and 15-mm expansion envelopes.

RESULTS

Of the 272 identified metastases, 3.3% (n = 9) were within 5 mm of the hippocampus, and 86.4% of metastases were greater than 15 mm from the hippocampus (n = 235). The most common location for metastatic disease was the frontal lobe (31.6%, n = 86). This was followed by the cerebellum (24.3%, n = 66), parietal lobe (16.9%, n = 46), temporal lobe (12.9%, n = 35), occipital lobe (7.7%, n = 21), deep brain nuclei (4.0%, n = 11), and brainstem (2.6%, n = 7).

CONCLUSIONS

Of the 100 patients, 8 had metastases within 5 mm of the hippocampus. Hence, a 5-mm margin around the hippocampus for conformal avoidance whole brain radiotherapy represents an acceptable risk, especially because these patients in the absence of any other intracranial disease could be salvaged using stereotactic radiosurgery. Moreover, we developed a hippocampal sparing tomotherapy plan as proof of principle to verify the feasibility of this therapy in the setting of brain metastases.

A Dosimetric Comparison of Accelerated Partial Breast Irradiation Techniques: Multicatheter Interstitial Brachytherapy, Three-Dimensional Conformal Radiotherapy, and Supine Versus Prone Helical Tomotherapy

PURPOSE

To compare dosimetrically four different techniques of accelerated partial breast irradiation (APBI) in the same patient.

METHODS AND MATERIALS

Thirteen post-lumpectomy interstitial brachytherapy (IB) patients underwent imaging with preimplant computed tomography (CT) in the prone and supine position. These CT scans were then used to generate three-dimensional conformal radiotherapy (3D-CRT) and prone and supine helical tomotherapy (PT and ST, respectively) APBI plans and compared with the treated IB plans. Dose-volume histogram analysis and the mean dose (NTD(mean)) values were compared.

RESULTS

Planning target volume coverage was excellent for all methods. Statistical significance was considered to be a p value <0.05. The mean V100 was significantly lower for IB (12% vs. 15% for PT, 18% for ST, and 26% for 3D-CRT). A greater significant differential was seen when comparing V50 with mean values of 24%, 43%, 47%, and 52% for IB, PT, ST, and 3D-CRT, respectively. The IB and PT were similar and delivered an average lung NTD(mean) dose of 1.3 Gy(3) and 1.2 Gy(3), respectively. Both of these methods were statistically significantly lower than the supine external beam techniques. Overall, all four methods yielded similar low doses to the heart.

CONCLUSIONS

The use of IB and PT resulted in greater normal tissue sparing (especially ipsilateral breast and lung) than the use of supine external beam techniques of 3D-CRT or ST. However, the choice of APBI technique must be tailored to the patient's anatomy, lumpectomy cavity location, and overall treatment goals.

A treatment planning study comparing whole breast radiation therapy against conformal, IMRT and tomotherapy for accelerated partial breast irradiation

PURPOSE AND BACKGROUND

Conventional early breast cancer treatment consists of a lumpectomy followed by whole breast radiation therapy. Accelerated partial breast irradiation (APBI) is an investigational approach to post-lumpectomy radiation for early breast cancer. The purpose of this study is to compare four external beam APBI techniques, including tomotherapy, with conventional whole breast irradiation for their radiation conformity index, dose homogeneity index, and dose to organs at risk.

METHODS AND MATERIALS

Small-field tangents, three-dimensional conformal radiation therapy, intensity-modulated radiation therapy and helical tomotherapy were compared for each of 15 patients (7 right, 8 left). One radiation conformity and two dose homogeneity indices were used to evaluate the dose to the target. The mean dose to organs at risk was also evaluated.

RESULTS

All proposed APBI techniques improved the conformity index significantly over whole breast tangents while maintaining dose homogeneity and without a significant increase in dose to organs at risk.

CONCLUSION

The four-field IMRT plan produced the best dosimetric results; however this technique would require appropriate respiratory motion management. An alternative would be to use a four-field conformal technique that is less sensitive to the effects of respiratory motion.

Breast movement during normal and deep breathing, respiratory training and set up errors: implications for external beam partial breast irradiation

This study was designed to evaluate interfraction and intrafraction breast movement and to study the effect of respiratory training on respiratory indices. Five patients were immobilized in supine position in a vacuum bag and three-dimensional set up errors, respiratory movement of the breast during normal and deep breathing, tidal volume and breath hold time were recorded. All patients underwent respiratory training and all the respiratory indices were re-evaluated at the end of training. Cumulative maximum movement error (CMME) was calculated by adding directional maximum set up error and maximum post training movement during normal breathing. The mean set up deviation was 1.3 mm (SD +/- 0.5 mm), 1.3 mm (SD +/- 0.3 mm) and 4.4 mm (SD +/- 2.6 mm) in the mediolateral, superoinferior and anteroposterior dimensions. Pre-training mean of the maximum marker movement during normal breathing was 1.07 mm, 1.94 mm and 1.86 mm in the mediolateral, superoinferior and anteroposterior dimensions. During deep breathing these values were 2 mm, 5.5 mm and 4.8 mm. While respiratory training had negligible effect on breast movement during normal breathing, it resulted in a modest reduction during deep breathing (p = 0.2). The mean CMME recorded for these patients was 3.4 mm, 4.5 mm and 7.1 mm in the mediolateral, superoinferior and anteroposterior dimension. Respiratory training also resulted in an increase in breath hold time from a mean of 31 s to 44 s (p = 0.04) and tidal volume from a mean of 560 cm(3) to 1160 cm(3) (p = 0.04). With patients immobilized in the vacuum bag the CMMEs are relatively less. Individualized directional margins may aid in reduction of planning target volume (PTV).

History of tomotherapy

Tomotherapy is the delivery of intensity modulated radiation therapy using rotational delivery of a fan beam in the manner of a CT scanner. In helical tomotherapy the couch and gantry are in continuous motion akin to a helical CT scanner. Helical tomotherapy is inherently capable of acquiring CT images of the patient in treatment position and using this information for image guidance. This review documents technological advancements of the field concentrating on the conceptual beginnings through to its first clinical implementation. The history of helical tomotherapy is also a story of technology migration from academic research to a university-industrial partnership, and finally to commercialization and widespread clinical use.

Dosimetric comparisons of helical tomotherapy treatment plans and step-and-shoot intensity-modulated radiosurgery treatment plans in intracranial stereotactic radiosurgery

PURPOSE

To evaluate dose conformity, dose homogeneity, and dose gradient in helical tomotherapy treatment plans for stereotactic radiosurgery, and compare results with step-and-shoot intensity-modulated radiosurgery (IMRS) treatment plans.

METHODS AND MATERIALS

Sixteen patients were selected with a mean tumor size of 14.65 +/- 11.2 cm3. Original step-and-shoot IMRS treatment plans used coplanar fields because of the constraint of the beam stopper. Retrospective step-and-shoot IMRS plans were generated using noncoplanar fields. Helical tomotherapy treatment plans were generated using the tomotherapy planning station. Dose conformity index, dose gradient score index, and homogeneity index were used in plan intercomparisons.

RESULTS

Noncoplanar IMRS plans increased dose conformity and dose gradient, but not dose homogeneity, compared with coplanar IMRS plans. Tomotherapy plans increased dose conformity and dose gradient, yet increased dose heterogeneity compared with noncoplanar IMRS plans. The average dose conformity index values were 1.53 +/- 0.38, 1.35 +/- 0.15, and 1.26 +/- 0.10 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The average dose homogeneity index values were 1.15 +/- 0.05, 1.13 +/- 0.04, and 1.18 +/- 0.09 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The mean dose gradient score index values were 1.37 +/- 19.08, 22.32 +/- 19.20, and 43.28 +/- 13.78 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The mean treatment time in tomotherapy was 42 +/- 16 min.

CONCLUSIONS

We were able to achieve better dose conformity and dose gradient in tomotherapy plans compared with step-and-shoot IMRS plans for intracranial stereotactic radiosurgery. However, tomotherapy treatment time was significantly larger than that in step-and-shoot IMRS.

Significant improvement in normal tissue sparing and target coverage for head and neck cancer by means of helical tomotherapy

PURPOSE

In order to explore the potential of helical Tomotherapy in the treatment of head and neck cancers (HNC), a planning study comparing our routinely delivered IMRT technique (dynamic MLC Varian 600CD Linac, inversely optimised by the Helios/Eclipse system) against two different Tomotherapy planning approaches was performed.

MATERIALS AND METHODS

In the first Tomotherapy plan (TOMO-a), we merely applied the same constraints used for the IMRT-Linac technique; in the second one (TOMO-b), we tried to stress the sparing of parotids and mandible while keeping PTV coverage and spinal cord Dmax similar to their values in the TOMO-a plan. Five patients with locally advanced oropharinx (n=3), hypopharinx (n=1) and larynx (n=1) cancer were considered. For each patient, CTV1 including neck nodes and the tumour was defined and was expanded with a margin of 0.5 cm (PTV1); then, CTV2 including high risk nodes and CTV3 including only T were defined and the corresponding PTV2/PTV3 were defined by a 0.5 cm expansion. IMRT and Tomotherapy planning were optimised to deliver 54 Gy in 30 fractions on PTV1 and 16.2 Gy in 9 fractions on PTV3; in the case a PTV2 was defined, 15 Gy were concomitantly delivered while delivering 16.2 Gy on PTV3. Separated plans for the two phases (Phase 1: first 30 fractions; Phase 2: last 9 fractions) were compared in terms of dose-volume histograms (DVH) and dose statistics on PTVs and OARs.

RESULTS

When considering Phase 1, Tomotherapy improved the homogeneity of the dose distribution within PTV1 while delivering the same prescribed dose (assessed to be the median dose to PTV): the fraction of PTV1 receiving more than 95% of the prescribed dose (V95%) increased from 90% (IMRT) to 96-97% for Tomotherapy plans. Dmax within PTV1 decreased from 60.3 Gy (IMRT) to 57.4 Gy (TOMO-a) and 58.7 Gy (TOMO-b). Spinal cord Dmax decreased from 31.6 Gy (IMRT) to 26.5 Gy (TOMO-a) and 24.6 Gy (TOMO-b). No attempts to further reduce spinal cord Dmax were done. Mean dose to the parotids decreased from 26.1 Gy (IMRT) to 25.1 Gy (TOMO-a) and 20.8 Gy (TOMO-b). Mandible was significantly better spared with Tomotherapy: mean dose decreased from 34.9 Gy (IMRT) to 34.0 Gy (TOMO-a) and 30.7 Gy (TOMO-b). When considering phase 2, the average gains (TOMO-b vs IMRT) were more modest and depended on the location of PTV2/PTV3.

CONCLUSIONS

Preliminary findings obtained in a sequential approach for HNC suggest that Tomotherapy has the potential to significantly improve the therapeutic ratio with respect to a conventional IMRT delivery method.

Irradiation du cancer du sein : incertitudes liées aux mouvements respiratoires et au repositionnement

Adjuvant Radiotherapy has been shown to significantly reduce locoregional recurrence but this advantage is associated with increased cardiovascular and pulmonary morbidities. All uncertainties inherent to conformal radiation therapy must be identified in order to increase the precision of treatment; misestimation of these uncertainties increases the potential risk of geometrical misses with, as a consequence, underdosage of the tumor and/or overdosage of healthy tissues. Geometric uncertainties due to respiratory movements or set-up errors are well known. Two strategies have been proposed to limit their effect: quantification of these uncertainties, which are then taken into account in the final calculation of safety margins and/or reduction of respiratory and set-up uncertainties by an efficient immobilization or gating systems. Measured on portal films with two tangential fields, CLD (central lung distance), defined as the distance between the deep field edge and the interior chest wall at the central axis, seems to be the best predictor of set-up uncertainties. Using CLD, estimated mean set-up errors from the literature are 3.8 and 3.2 mm for the systematic and random errors respectively. These depend partly on the type of immobilization device and could be reduced by the use of portal imaging systems. Furthermore, breast is mobile during respiration with motion amplitude as high as 0.8 to 10 mm in the anteroposterior direction. Respiratory gating techniques, currently on evaluation, have the potential to reduce effect of these movements. Each radiotherapy department should perform its own assessments and determine the geometric uncertainties with respect of the equipment used and its particular treatment practices. This paper is a review of the main geometric uncertainties in breast treatment, due to respiration and set-up, and solutions proposed to limit their impact.