Nomogram to predict ipsilateral breast relapse based on pathology review from the EORTC 22881-10882 boost versus no boost trial

Background and purpose

The EORTC 22881-10882 trial showed that for patients treated with breast conserving therapy (BCT), a 16 Gy boost dose significantly improved local control, but increased the risk of breast fibrosis. A model to estimate the risk of ipsilateral breast relapse (IBR) already exists, but now a model has been developed which takes boost treatment into account and is based on centrally reviewed pathology.

Materials and methods

A Cox model was developed based on central pathology review data and clinical data of 1603 patients from the EORTC 22881-10882 trial with a median follow-up of 11.5 years. From a predefined set of variables, predictors with a maximal effect on 10-year IBR rate >4% were retained in the model. Bootstrap re-sampling was used to assess model calibration and discrimination. The results are presented in the form of a nomogram.

Results

Apart from young age and no boost, presence of DCIS adjacent to the invasive tumor was associated with increased risk of IBR (HR 1.96, p = 0.001). Patients with high grade invasive tumors were younger than patients with low/intermediate grade (p < 0.0001). The nomogram includes histologic grade, DCIS, tumor diameter, age, tamoxifen, chemotherapy, and boost with a concordance probability estimate of 0.68.

Conclusions

The nomogram for predicting IBR 10 years after BCT includes seven factors, with young age, presence of DCIS and boost treatment as the most dominant factors. The nomogram estimates IBR and confirms the importance of a boost dose. Combined with a model to predict fibrosis published previously, the nomogram presented here may assist in decision making for individual patients.     

Electronic portal images (EPIs) based position verification for the breast simultaneous integrated boost (SIB) technique

Background and purpose

To develop a method based on electronic portal images (EPIs) for the position verification of breast cancer patients that are treated with a simultaneous integrated boost (SIB) technique.

Method

3D setup errors of the breast outline and the thoracic wall were determined from EPIs of the tangential treatment fields and anterior posterior (AP) verification field. The method was verified with repeated CT scans of 38 patients with an average setup error larger than 5 mm.

Result

The 3D position deviation of the boost volume can best be determined from the position deviation of the breast outline in the ventrodorsal direction and the thoracic wall in the lateral and longitudinal directions from the tangential and AP EPIs. The method gives an average overestimation of the deviation of the boost volume in the ventrodorsal, lateral and longitudinal directions by 28%, 20% and 6%, respectively and an average underestimation of the deviation of the whole breast by 32%, 17% and 39%.

Conclusions

The described method is superior to using tangential EPIs only and is recommended for position verification of breast cancer patients that are treated with a SIB technique if no Cone beam CT (CBCT) or fiducial markers can be used.     

Target volume delineation variation in radiotherapy for early stage rectal cancer in the Netherlands

Purpose

The aim of this study was to measure and improve the quality of target volume delineation by means of national consensus on target volume definition in early-stage rectal cancer.

Methods and materials

The CTV’s for eight patients were delineated by 11 radiation oncologists in 10 institutes according to local guidelines (phase 1). After observer variation analysis a workshop was organized to establish delineation guidelines and a digital atlas, with which the same observers re-delineated the dataset (phase 2). Variation in volume, most caudal and cranial slice and local surface distance variation were analyzed.

Results

The average delineated CTV volume decreased from 620 to 460 cc (p < 0.001) in phase 2. Variation in the caudal CTV border was reduced significantly from 1.8 to 1.2 cm SD (p = 0.01), while it remained 0.7 cm SD for the cranial border. The local surface distance variation (cm SD) reduced from 1.02 to 0.74 for anterior, 0.63 to 0.54 for lateral, 0.33 to 0.25 for posterior and 1.22 to 0.46 for the sphincter region, respectively.

Conclusions

The large variation in target volume delineation could significantly be reduced by use of consensus guidelines and a digital delineation atlas. Despite the significant reduction there is still a need for further improvement.     

Preoperative radiotherapy and local excision of rectal cancer with immediate radical re-operation for poor responders

Background and purpose

To report an early analysis of prospective study exploring preoperative radiotherapy and local excision in rectal cancer.

Materials and methods

Mucosa at tumour edges was tattooed. Patients with cT1-3N0 tumour <3-4 cm were treated with either 5 × 5 Gy + 4 Gy boost (N = 31) or chemoradiation (50.4 Gy + 5.4 Gy boost, 1.8 Gy per fraction + 5-fluorouracyl and leucovorin; N = 13). Thirteen patients from the short-course group were unfit for chemotherapy. The interval from radiation to full-thickness local excision was 6 weeks. The protocol called for conversion to a transabdominal surgery in case of ypT2-3 disease or positive margin.

Results

The postoperative complications requiring hospitalization were recorded in 9% of patients. The rate of pathological complete response was 41%. The rate of patients requiring conversion was 34%; however, 18% actually underwent conversion and the remaining 16% refused or were unfit. During the 14 months of median follow-up, local recurrence was detected in 7% of patients and all underwent salvage surgery. Of 19 patients in whom initially anterior resection was likely, 16% had abdominoperineal resection performed for a conversion or as a rescue procedure.

Conclusion

Our study suggests that the short-course radiation prior to local excision is a treatment option for high-risk patients.     

Planning the breast boost: How accurately do surgical clips represent the CT seroma?

Background and purpose

To measure the distance between surgical clips and edge of CT-defined seroma in a coronal plane in women who have undergone wide local excision of breast cancer and to evaluate dosimetric coverage of CT-defined boost volumes by conventional clip-based electron fields.

Materials and methods

Planning CT images of 30 lumpectomy cavities from 30 patients were reviewed. All seroma cavities had at least 4 clips and Cavity Visualization Score ?3. Distances between clips and seroma edge (D_c-s) were measured at the radial margins for each patient. Clips-based electron fields were generated by including all the clips with 2 cm margin in the coronal plane and three-dimensional conformal radiotherapy plans (3D-CRT) were devised based on CT tumor beds (CT-TBs). The parameters of dose-volume histogram between the two boost treatment plans were analyzed.

Results

The mean seroma edge extended beyond the clips by 0.3-0.5 cm. In all 120 D_c-ss, 76.7% were ?0.5 cm, 8.3% were >1 cm and 15% were between 0.5 and 1 cm. Twenty patients (20/30) had D_c-smax (The maximal D_c-s of each patient) > 0.5 cm and 7 patients had D_c-smax > 1 cm. With the electron fields, only 46.7% (14/30) had D₉₀ (The minimal dose received by 90% of the planning target volume (PTV)) > 90% and geographical miss (any portion of the PTV receiving <50% of the prescribed dose) was found in 36.7% (11/30). D_c-smax > 0.5 cm was associated with D₉₀ < 90% (P < 0.001) and >1 cm was associated with geographic miss (P = 0.001).

Conclusions

Surgical clips are not always consistent with the edge of seroma. Electron boost field based on clips leads to insufficient dose coverage to the CT-TB. 3D-CRT planning should be considered to ameliorate the dose coverage to the tumor bed.     

Adjuvant chemoradiation versus surgery alone for adenocarcinoma of the ampulla of Vater

Background and purpose

To examine the role of adjuvant chemoradiation (CRT) in patients with resected ampullary adenocarcinoma.

Materials and methods

The records of patients who underwent curative surgery for ampullary adenocarcinoma at a single institution between 1992 and 2007 were reviewed. Final analysis included 111 patients, 45% of which also received adjuvant CRT.

Results

Median overall survival (OS) was 36.2 months for all patients. Adverse prognostic factors for OS included T stage (T3/4 vs. T1/T2, p = 0.046), node status (positive vs. negative, p < 0.001), and histological grade (grade 3 vs. 1/2, p = 0.09). Patients receiving CRT were more likely to have advanced T-stage (p = 0.001), node positivity (p < 0.001), and poor histologic grade (p = 0.015). Patients who received CRT were also significantly younger (p = 0.001). On univariate analysis, adjuvant CRT failed to result in a significant difference in survival when compared to surgery alone (median OS: 33.4 vs. 36.2 months, p = 0.969). Patients with node-positive resections who underwent CRT had a non-significant improvement in survival (median OS: 21.6 vs. 13.0 months, p = 0.092). Thirty-three percent of patients developed distant metastasis. Common sites of distant metastasis included liver (23%) and peritoneum (7%).

Conclusions

Adjuvant chemoradiation following curative resection for ampullary adenocarcinoma did not lead to a statistically significant benefit in overall survival. A significant proportion of patients still developed distant metastatic disease suggesting a need for more effective systemic adjuvant therapy.     

Target volume shape variation during hypo-fractionated preoperative irradiation of rectal cancer patients

Purpose

To quantify the day-to-day target volume shape variation in rectal-cancer patients treated with preoperative 5 × 5 Gy radiotherapy.

Materials and methods

For 27 patients a prone position plan-CT (pCT) and five daily pre-treatment cone-beam-CT (CBCT) scans were acquired. A sub-region of the CTV (MesoRect, anus up to the cranial end of the mesorectal-fascia) was delineated on all scans. The MesoRect deformation was quantified by the distance between pCT- and CBCT-delineations and was stored in surface-maps. Finally, the influence of bladder and rectum filling on MesoRect deformation was evaluated. Data were analyzed for male and female patients separately.

Results

A large range of systematic and random deformations, 1-7 mm (1SD), on different areas of the MesoRect were found. The maximum deformations were located at the upper-anterior-side of the MesoRect. For females the errors were up to 3 mm larger than for males. Small correlations, r² ? 0.4, were found with changes in bladder volume. Larger correlations, r² ? 0.7, were found for rectal volume in a distinctive area in the upper-half of the MesoRect.

Conclusions

Substantial and heterogeneous deformations of the MesoRect were found. Therefore different PTV margins in positions along the cranio-caudal axis, in the anterior-posterior direction. Margins should also be larger for female patients compared to male patients.     

Significance of an exon 2 G4C14-to-A4T14 polymorphism in the p73 gene on survival in rectal cancer patients with or without preoperative radiotherapy

Background and purpose

An exon 2 G4C14 → A4T14 polymorphism in the p73 gene was shown to be related to survival in several types of cancers, including colorectal cancer. The purpose was to investigate if this polymorphism was related to survival in rectal cancer patients with or without preoperative radiotherapy.

Materials and methods

DNA extracted from tissue of 138 rectal cancer patients that received preoperative radiotherapy or had surgery alone was typed for the polymorphism by PCR using confronting two-pair primers.

Results

Among patients, 69% had GC/GC genotype, 27% had GC/AT and 4% had AT/AT. In the radiotherapy group, patients carrying the AT (GC/AT + AT/AT) allele had stronger expression of p53 (p = 0.001) and survivin protein (p = 0.03) than those carrying the GC/GC genotype. Further, among patients receiving preoperative radiotherapy the GC/GC genotype tended to be related to better survival (p = 0.20). Patients with GC/GC genotype, along with negative p53 and weak survivin expression showed better survival than the other patients (p = 0.03), even after adjusting for TNM stage and tumor differentiation (p = 0.01, RR, 7.63, 95% CI, 1.50-38.74). In the non-radiotherapy group, the polymorphism was not related to survival (p = 0.74).

Conclusions

Results suggest that the p73 G4C14 → A4T14 polymorphism could be one factor influencing outcome of preoperative radiotherapy in rectal cancer patients.     

Sparing the penile bulb in the radical irradiation of clinically localised prostate carcinoma: A comparison between MRI and CT prostatic apex definition in 3DCRT, Linac-IMRT and Helical Tomotherapy

Background and purpose

To assess the impact of using MRI and Helical Tomotherapy (HT) compared to 3DCRT and dynamic IMRT on the dose to the penile bulb (PB).

Materials and methods

Eight patients diagnosed with prostate cancer entered a treatment protocol including CT and MRI simulation. The prostate apex was defined on both MRI and CT. Treatment plans (HT, Linac-IMRT, 3DCRT and conventional technique), were elaborated on both MRI and CT images. A dose of 71.4 Gy (2.55 Gy/fraction) was prescribed; it was requested that PTVs be covered by 95% isodose line. The mean dose and V50 of PB were evaluated.

Results

PTV-MRI plans reduced PB mean dose and V50 compared to PTV-CT plans. This improvement, deriving also from the treatment modality, was 89% for 3DCRT, 99% for Linac-IMRT and 97% for HT (p < 0.01), considering V50. Conventional plans resulted in a significantly higher mean PB dose/V50 compared to 3DCRT-PTV-CT (+27%/+38%), Linac-IMRT-PTV-CT (+42%/+57%) and HT-PTV-CT (+32%/+48%) (p < 0.01). The comparison between conventional and PTV-MRI techniques showed a still larger increase: +73%/+93% 3DCRT; +86%/+99% Linac-IMRT; +56%/+99% HT (p < 0.01). The PB mean dose reduction with Linac-IMRT compared to 3DCRT was 24% (p = 0.034) and 40% (p = 0.027) for PTV-CT and PTV-MRI, respectively. This gain remained significant even when comparing Linac-IMRT to HT: 21% (p = 0.07) PTV-CT and 68% (p = 0.00002) PTV-MRI. HT was superior to 3DCRT with respect to PTV-CT (average gain 4%, p = 0.044), whereas it resulted to be detrimental considering PTV-MRI (26 Gy vs 16.5 Gy), possibly due to the helical delivery of HT; however, in a patient where the distance bulb-PTV <1 cm, HT provided better PB sparing than 3DCRT (29.5 Gy vs 45.2 Gy).

Conclusions

MRI allowed efficient sparing of PB irrespective of the treatment modality. Linac-IMRT was shown to further reduce the dose to the bulb compared to 3DCRT and HT.     

Functional image-based radiotherapy planning for non-small cell lung cancer: A simulation study

Background and purpose

To investigate the incorporation of data from single-photon emission computed tomography (SPECT) or hyperpolarized helium-3 magnetic resonance imaging (³He-MRI) into intensity-modulated radiotherapy (IMRT) planning for non-small cell lung cancer (NSCLC).

Material and methods

Seven scenarios were simulated that represent cases of NSCLC with significant functional lung defects. Two independent IMRT plans were produced for each scenario; one to minimise total lung volume receiving ?20 Gy (V₂₀), and the other to minimise only the functional lung volume receiving ?20 Gy (FV₂₀). Dose-volume characteristics and a plan quality index related to planning target volume coverage by the 95% isodose (V_PTV95/FV₂₀) were compared between anatomical and functional plans using the Wilcoxon signed ranks test.

Results

Compared to anatomical IMRT plans, functional planning reduced FV₂₀ (median 2.7%, range 0.6-3.5%, p = 0.02), and total lung V₂₀ (median 1.5%, 0.5-2.7%, p = 0.02), with a small reduction in mean functional lung dose (median 0.4 Gy, 0-0.7 Gy, p = 0.03). There were no significant differences in target volume coverage or organ-at-risk doses. Plan quality index was improved for functional plans (median increase 1.4, range 0-11.8, p = 0.02).

Conclusions

Statistically significant reductions in FV₂₀, V₂₀ and mean functional lung dose are possible when IMRT planning is supplemented by functional information derived from SPECT or ³He-MRI.     

Concomitant intensity modulated boost during whole breast hypofractionated radiotherapy - A feasibility and toxicity study

Background

Breast cancer sensitivity to large fraction size may be enhanced using hypofractionated concomitant boost radiotherapy (CBRT), thereby shortening overall treatment time. This ethics approved, prospective single cohort feasibility study was designed to evaluate the dosimetry and toxicity of CBRT using an intensity-modulated radiotherapy (IMRT) technique, compared with a standard sequential boost technique (SBT).

Methods

Fifteen women (11 right-sided; 4 left-sided) received 42.4 Gy to the whole breast and an additional 10.08 Gy to the tumor bed in 16 daily fractions, using IMRT and standard dose constraints. Each patient was replanned with the SBT, using mixed photon-electrons. Clinical target volume (CTV), dose evaluation volume (DEV), and organs at risk (OAR) dose distributions were compared with the SBT. Toxicity and treatment times were prospectively recorded.

Results

All 15 CBRT plans achieved the desired CTV (V_49.9Gy ? 99%) and DEV (V_49.9Gy ? 95%), coverage of the boost, compared with only 10 (66.7%, p = 0.03), and 12 (80%, p = 0.125) SBT plans, respectively. Ipsilateral lung (p < 0.0001), and heart (right-sided, p = 0.001; left-sided, p = 0.13) doses were lower. Grade 3 acute toxicity occurred in 1 (6.7%) patient. At 1 year, two (13.3%) additional patients had overall grade 2 late toxicity, compared with baseline. No grade 3-4 late toxicity was observed.

Conclusions

CBRT using IMRT improved boost coverage and lowered OAR doses, compared with SBT. Toxicities were acceptable using a daily boost of 3.28 Gy. While resource utilization was greater, overall treatment time was reduced.     

Intensity modulated radiotherapy in the management of sacral chordoma in primary versus recurrent disease

Purpose

To investigate treatment outcome in patients suffering from sacral chordoma after intensity modulated radiotherapy (IMRT) for primary versus recurrent disease.

Material/methods

We report on 34 patients with histologically proven sacral chordoma. Seventeen patients were treated at time of initial diagnosis with post-operative IMRT (n = 13) or with IMRT alone (n = 4). Seventeen patients were treated in recurrent disease after surgery (n = 11) or with radiotherapy alone (n = 6). Median total dose to the boost volume (PTV2) was 66 Gy (range, 72-54) with 2 Gy per fraction using an integrated boost concept. Median dose to target volume (PTV1) was 54 Gy in 1.8 Gy.

Results

Local control was 35% (12/34) and overall survival 74% (25/34) after a median follow-up of 4.5 years. Actuarial local control was 79%, 55% and 27% after 1, 2 and 5 years, respectively. Local control was significantly higher in patients treated for primary tumors (p < 0.03) and in total doses >60 Gy (p < 0.01). Actuarial overall survival was 97%, 91% and 70% after 1, 2 and 5 years, respectively.

Conclusion

These data demonstrate that local control after IMRT is higher in patients treated for primary tumors and using higher radiation doses. Therefore, we recommend radiotherapy as part of initial treatment in sacral chordoma.     

Localization of the surgical bed using supine magnetic resonance and computed tomography scan fusion for planification of breast interstitial brachytherapy

Purpose

To evaluate the feasibility of supine breast magnetic resonance imaging (MR) for definition and localization of the surgical bed (SB) after breast conservative surgery. To assess the inter-observer variability of surgical bed delineation on computed tomography (CT) and supine MR.

Materials and methods

Patients candidate for breast brachytherapy and no contra-indications for MR were eligible for this study. Patients were placed in supine position, with the ipsilateral arm above the head in an immobilization device. All patients underwent CT and MR in the same implant/treatment position. Four points were predefined for CT-MRI image fusion. The surgical cavity was drawn on CT then MRI, by three independent observers. Fusion and analysis of CT and MR images were performed using the ECLIPSE treatment planning software.

Results

From September 2005 to November 2008, 70 patients were included in this prospective study. For each patient, we were able to acquire axial T1 and T2 images of good quality. Using the predefined fusion points, the median error following the fusion was 2.7 mm. For each observer, volumes obtained on MR were, respectively, 30%, 38% and 40% smaller than those derived from CT images. A highly significant inter-observer variability in the delineation of the SB on CT was demonstrated (p < 0.0001). On the contrary, all three observers agreed on the volume of the SB drawn on MR.

Conclusion

Supine breast MRI yields a more precise definition of the SB with a smaller inter-observer variability than CT and may obviate the need for surgical clips. The volume of the SB is smaller with MRI. In our opinion, CT-MRI fusion should be used for SB delineation, in view of partial breast irradiation.     

Dose-escalation using intensity-modulated radiotherapy for prostate cancer - Evaluation of the dose distribution with and without F-choline PET-CT detected simultaneous integrated boost

Background and purpose

The aim of the study was to evaluate the impact of a dose escalation to an ¹⁸F-choline PET-CT defined simultaneous integrated boost (IB) on the dose distribution and changes of the equivalent uniform dose (EUD).

Materials and methods

PET-CT was performed in 12 consecutive patients for treatment planning. An intraprostatic lesion was defined by a tumour-to-background uptake value ratio >2 (GTV_PET). Dose escalation was focused only on the intraprostatic lesion. Two comparisons were evaluated: whole prostate irradiation to 76 Gy ± boost to 80 Gy (C1) and whole prostate irradiation to 66.6 Gy ± boost to 83.25 Gy (C2).

Results

PTV/GTV_PET + margins were covered by a mean EUD of 75.9/76.1 Gy vs. 77.1/80.1 Gy (C1) and 66.5/66.2 Gy vs. 71.1/82.9 Gy (C2) (p < 0.01, respectively). Concerning the organs at risk, EUD increased slightly with an additional boost (mean EUD for bladder: C1 53.2 Gy vs. 53.8 Gy; C2 43.0 Gy vs. 45.1 Gy; for rectum: C1 52.0 Gy vs. 52.6 Gy; C2 43.0 Gy vs. 45.4 Gy; p < 0.01, respectively). The distance to the organs at risk had a significant impact on the respective maximum doses in the treatment plans with IB.

Conclusions

Treatment planning with IB allows an individually adapted dose escalation. The therapeutic ratio can be improved by a considerable dose escalation to the macroscopic tumour, but only minor EUD changes to the bladder and rectum.     

Chromosomal aberrations in peripheral blood lymphocytes of prostate cancer patients treated with IMRT and carbon ions

Background and purpose

To investigate the cytogenetic damage in blood lymphocytes of patients treated for prostate cancer with different radiation qualities and target volumes.

Materials and methods

Twenty patients receiving carbon-ion boost irradiation followed by IMRT or IMRT alone for the treatment of prostate cancer entered the study. Cytogenetic damage induced in peripheral blood lymphocytes of these patients was investigated at different times during the radiotherapy course using Giemsa staining and mFISH. A blood sample from each patient was taken before initiation of radiation therapy and irradiated in vitro to test for individual radiosensitivity. In addition, in vitro dose-effect curves for the induction of chromosomal exchanges by X-rays and carbon ions of different energies were measured.

Results

The yield of chromosome aberrations increased during the therapy course, and the frequency was lower in patients irradiated with carbon ions as compared to patients treated with IMRT with similar target volumes. A higher frequency of aberrations was measured by increasing the target volume. In vitro, high-LET carbon ions were more effective than X-rays in inducing aberrations and yielded a higher fraction of complex exchanges. The yield of complex aberrations observed in vivo was very low.

Conclusion

The investigation showed no higher aberration yield induced by treatment with a carbon-ion boost. In contrast, the reduced integral dose to the normal tissue is reflected in a lower chromosomal aberration yield when a carbon-ion boost is used instead of IMRT alone. No cytogenetic “signature” of exposure to densely ionizing carbon ions could be detected in vivo.     

Sequentially delivered boost plans are superior to simultaneously delivered plans in head and neck cancer when the boost volume is located further away from the parotid glands

Purpose

To find parameters that predict which head and neck patients benefit from a sequentially delivered boost treatment plan compared to a simultaneously delivered plan, with the aim to spare the salivary glands.

Methods and materials

We evaluated 50 recently treated head and neck cancer patients. Apart from the clinical plan with a sequentially (SEQ) given boost using an Intensity Modulated Radiotherapy Technique (IMRT), a simultaneous integrated boost (SIB) technique plan was constructed with the same beam set-up. The mean dose to the parotid glands was calculated and compared. The elective nodal areas were bilateral in all cases, with a boost on either one side or both sides of the neck.

Results

When the parotid gland volume and the Planning Target Volume (PTV) for the boost overlap there is on average a lower dose to the parotid gland with a SIB technique (−1.2 Gy), which is, however, not significant (p = 0.08).For all parotid glands with no boost PTV overlap, there is a benefit from a SEQ technique compared to a SIB technique for the gland evaluated (on average a 2.5 Gy lower dose to the parotid gland, p < 0.001). When the distance between gland and PTV is 0-1 cm, this difference is on average 0.8 Gy, for 1-2 cm distance 2.9 Gy and for glands with a distance greater than 2 cm, 3.3 Gy. When the lymph nodes on the evaluated side are also included in the boost PTV, however, this relationship between the distance and the gain of a SEQ seems less clear.

Conclusions

A sequentially delivered boost technique results in a better treatment plan for most cases, compared to a simultaneous integrated boost IMRT technique, if the boost PTV is more than 1 cm away from at least one parotid gland.     

Comparison of conventional radiotherapy and intensity-modulated radiotherapy for post-operative radiotherapy for primary extremity soft tissue sarcoma

Introduction

Doses in conventional radiotherapy for extremity soft tissue sarcoma (STS) potentially exceed normal tissue tolerances. This study compares 3D-conformal radiotherapy (3D-CRT) with intensity-modulated radiotherapy (IMRT) in optimising target volume coverage and minimising integral dose to organs-at-risk (OAR).

Methods and materials

Ten patients undergoing post-operative radiotherapy for extremity STS were assessed. PTV₁ was defined as tumour bed plus 5 cm superiorly/inferiorly and 3 cm circumferentially, PTV₂ was defined as 2 cm isotropically. OAR were defined as whole femur, neurovascular bundle, tissue corridor and normal tissue outside PTV₁. For each patient 2-phase 3D-CRT was compared to 2/3 field (2/3f) and 4/5 field (4/5f) IMRT with simultaneous integrated boost (SIB). The primary planning objective was to minimise femur and skin corridor dose. Volumetric analysis and conformity and heterogeneity indices were used for plan comparison.

Results

A planning protocol containing dose/volume constraints for target and OAR was defined. 4/5f IMRT showed greatest conformity and homogeneity. IMRT resulted in significantly lower femur V45 using 2/3f (p = 0.01) and 4/5f (p = 0.0009) than 3D-CRT. 4/5f IMRT resulted in significantly lower normal tissue V55 (p = 0.004) and maximum dose (p = 0.04) than 3D-CRT.

Conclusions

A reproducible set of planning guidelines and dose-volume constraints for 3D-CRT and IMRT planning for extremity sarcomas was devised. 4/5f IMRT with SIB resulted in better target coverage and significantly decreased OAR dose. Further evaluation of this technique within a clinical trial is recommended to demonstrate that the technical benefit of the more complex technique translates into patient-derived benefit by reducing late toxicity.     

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_54.23Gy = 12.47% vs. 30.83%; p < 0.001). Ipsilateral lung V_20Gy (6.34% vs. 10.17%; p < 0.001), V_5Gy (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_30Gy (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_5Gy. Contralateral breast V_5Gy (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.