Advantages Of Intensity-modulated Radiation Therapy Research Articles

Outcomes of patients with nasopharyngeal carcinoma treated with intensity-modulated radiotherapy.

Nasopharyngeal cancer shows a good response to intensity-modulated radiotherapy. However, there is no clear evidence for the benefits of routine use of image-guided radiotherapy. The purpose of this study was to perform a retrospective investigation of the treatment outcomes, treatment-related complications and prognostic factors for nasopharyngeal cancer treated with intensity-modulated radiotherapy and image-guided radiotherapy techniques. Retrospective analysis was performed on 326 consecutive nasopharyngeal cancer patients treated between 2004 and 2015. Potentially significant patient-related and treatment-related variables were analyzed. Radiation-related complications were recorded. The 5-year overall survival and disease-free survival rates of these patients were 77.9% and 70.5%, respectively. Age, AJCC (American Joint Committee on Cancer) stage, retropharyngeal lymphadenopathy, treatment interruption and body mass index were independent prognostic factors for overall survival. Age, AJCC stage, retropharyngeal lymphadenopathy, image-guided radiotherapy and body mass index were independent prognostic factors for disease-free survival. In conclusion, intensity-modulated radiotherapy significantly improves the treatment outcomes of nasopharyngeal cancer. With the aid of image-guided radiotherapy, the advantage of intensity-modulated radiotherapy might be further amplified.

Dosimetry of conformal dynamic arc radiotherapy and intensity modulated radiotherapy in unresectable cholangiocarcinoma

Background: Radiotherapy in cholangiocrcinoma has to overcome organ tolerance of the upper abdomen. Hi-technology radiotherapy may improve conformity and reduce dose to those organ. Objective: Quantitatively compare the dosimetry of conformal dynamic arc radiotherapy (CD-arcRT) and intensity modulated radiotherapy (IMRT) in unresectable cholangiocarcinoma. Material and methods: Eleven cases of unresectable cholangiocarcinoma were re-planned with IMRT and CDarcRT at King Chulalongkhorn Memorial Hospital between 20 September 2004 and 31 December 2005. Both the planning techniques were evaluated using the dose volume histogram of the planning target volume and organ at risk. The conformation number and dose to critical normal structures were used to determine the techniques. Results: IMRT technique was significantly conformed to the planning target volume than CD-arcRT in term of conformation number. For critical structure, IMRT significantly reduced the radiation dose to liver in terms of mean liver dose, V30Gy and V20Gy of the right kidney. Conclusion: The advantage of IMRT was more conformity and reduced dose to critical structure compared with CD-arcRT, but there was no difference between these techniques in terms of V20Gy of left kidney and maximum dose to the spinal cord.

A Formal Assessment of the Dosimetric Advantages of Intensity-Modulated Radiation Therapy in Locally Advanced Lung Cancer

A Formal Assessment of the Dosimetric Advantages of Intensity-Modulated Radiation Therapy in Locally Advanced Lung Cancer

A study of finite discontinuity-volumetric modulated arc therapy for mid-and distal-Esophageal Carcinoma

Objective To implement the finite discontinuity-volumetric modulated arc therapy (FD-VMAT) in the Pinnacle planning system, and to investigate its clinical significance. Methods Eight patients with thoracic esophageal cancer in our hospital were enrolled as subjects. FD-VMAT was fulfilled in the Pinnacle planning system using a developed program. FD-VMAT, VMAT, and fixed-field intensity-modulated radiotherapy (IMRT) plans were designed for each patient. The conformity index (CI) and homogeneity index (HI) of the planning target volume (PTV), doses to organs at risk, passing rate for plan verification, number of monitor units, and treatment time were used to evaluate the plans. Comparison between different plans was made by paired t test. Results For the PTV, there was no significant difference in CI between FD-VMAT and VAMT (P=0.186); FD-VMAT had a significantly worse HI than VMAT (P=0.001); however, both the CI and HI were significantly improved in FD-VMAT than in IMRT (P=0.006, 0.002). Compared with IMRT, FD-VMAT, retaining the advantage of VMAT, had pulmonary V20 and V30 significantly reduced by 19.79% and 20.32%, respectively (P=0.000, 0.000). For the pulmonary low-dose regions (≤V5), FD-VMAT retained the advantage of IMRT and had lower doses than VMAT.Particularly, pulmonary V2 was significantly reduced by 16.79%(P=0.000). The mean lung dose was significantly lower in FD-VMAT than in VMAT or IMRT (P=0.001, 0.000). There were no significant differences in D1cc to spinal cord PRV, heart V30, or passing rate for plan verification between the three therapies. The heart V40 and mean heart dose in FD-VMAT were similar to those in VMAT (P=0.175, 0.468), but significantly lower than those in IMRT (P=0.021, 0.002). FD-VMAT had a larger number of monitor units and longer treatment time than VMAT.Compared with IMRT, the number of monitor units and treatment time were reduced by 13.6% and 49.6% in FD-VMAT, respectively. Conclusions Compared with VMAT and IMRT, the application of the developed FD-VMAT in the treatment of thoracic esophageal cancer can further reduce the lung dose while keeping the PTV coverage, protection of the heart and spinal cord, and high efficacy. FD-VMAT is a new therapy available for thoracic esophageal cancer. Key words: Finite discontinuity-volumetric modulated arc therapy; Volumetric-modulated arc therapy; Intensity-modulated radiotherapy; Pinnacle treatment planning system; Esophageal Neoplasm

Global and health-related quality of life after intensity-modulated radiation therapy for head and neck cancer

This study aims to evaluate the current literature regarding the effects of conventional radiation therapy (CRT) versus intensity-modulated radiation therapy (IMRT) on global quality of life (QoL) among patients treated for head and neck cancer. A PubMed literature review was performed. Only articles comparing global QoL scores in head and neck cancer patients treated with CRT versus IMRT were included. Studies were scrutinized for methodology, level of evidence and limitations. Outcomes were evaluated for external validity, level of evidence and applicability. Between 2005 and 2012, 14 eligible studies (six prospective, two randomized controlled trials) were identified. Although all presented data comment on the advantages of IMRT, differences in study design made comparisons difficult. The vast majority of these were also limited by relatively small sample sizes and heterogeneity with respect to patient and treatment-related characteristics. Although more robust evidence is needed in the future, the published data reasonably support the benefits of IMRT as compared with CRT (either 2D or 3D) in improving QoL, beginning at approximately 3–6 months post-treatment, and possibly potentiating with time up to 2 and 3 years.

Intensity-modulated radiation therapy and volumetric-modulated arc therapy for adult craniospinal irradiation—A comparison with traditional techniques

Craniospinal irradiation (CSI) poses a challenging planning process because of the complex target volume. Traditional 3D conformal CSI does not spare any critical organs, resulting in toxicity in patients. Here the dosimetric advantages of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) are compared with classic conformal planning in adults for both cranial and spine fields to develop a clinically feasible technique that is both effective and efficient. Ten adult patients treated with CSI were retrospectively identified. For the cranial fields, 5-field IMRT and dual 356° VMAT arcs were compared with opposed lateral 3D conformal radiotherapy (3D-CRT) fields. For the spine fields, traditional posterior-anterior (PA) PA fields were compared with isocentric 5-field IMRT plans and single 200° VMAT arcs. Two adult patients have been treated using this IMRT technique to date and extensive quality assurance, especially for the junction regions, was performed. For the cranial fields, the IMRT technique had the highest planned target volume (PTV) maximum and was the least efficient, whereas the VMAT technique provided the greatest parotid sparing with better efficiency. 3D-CRT provided the most efficient delivery but with the highest parotid dose. For the spine fields, VMAT provided the best PTV coverage but had the highest mean dose to all organs at risk (OAR). 3D-CRT had the highest PTV and OAR maximum doses but was the most efficient. IMRT provides the greatest OAR sparing but the longest delivery time. For those patients with unresectable disease that can benefit from a higher, definitive dose, 3D-CRT–opposed laterals are the most clinically feasible technique for cranial fields and for spine fields. Although inefficient, the IMRT technique is the most clinically feasible because of the increased mean OAR dose with the VMAT technique. Quality assurance of the beams, especially the junction regions, is essential.

Intensity-modulated Radiotherapy in the Treatment of Gynaecological Cancers

Intensity-modulated radiotherapy (IMRT) is a newer method of radiotherapy that uses intensity-modulated beams that can provide multiple intensity levels for any single beam direction and any single source position allowing concave dose distributions and dose gradients with narrower margins than those possible using conventional methods. IMRT is ideal for treating complex treatment volumes and avoiding close proximity organs at risk that may be dose limiting and provides increased tumour control through an escalated dose and reduces normal tissue complications through organ at risk sparing. Given the potential advantages of IMRT and the availability of IMRT-enabled treatment planning systems and linear accelerators, IMRT has been introduced in a number of disease sites. This systematic review examined the evidence for IMRT in the treatment of gynaecological cancers to quantify the potential benefits of this new technology and to make recommendations for radiation treatment programmes considering adopting this technique. Findings were based on a review of four cohort studies, one of which was prospective, including a total of 619 patients. If reducing acute and chronic toxicity are the main outcomes of interest, then IMRT may be considered over three-dimensional conformal radiotherapy for women with gynaecological cancers; if disease-related outcomes are the main outcomes of interest, there are insufficient data to recommend IMRT over three-dimensional conformal radiotherapy. Future research should focus on prospective multicentre studies reporting on both acute and chronic toxicity as well as survival and recurrence. Dose escalation studies should be carried out to investigate the effect of higher doses on disease.

Inverse-probability weighted and propensity score-based analysis of long-term clinical outcomes comparing 3D conformal radiotherapy (3DCRT) with intensity-modulated radiation therapy (IMRT) in the treatment of esophageal cancer.

e14548 Background: IMRT has clear dosimetric advantages in the sparing of normal tissues when compared to the more conventional 3DCRT technique for the treatment of esophageal cancer, but there is currently no clinical outcomes evidence to support the use of IMRT. We hypothesized that the theoretical advantages of IMRT should translate to clinical outcomes benefits compared to 3DCRT. Methods: We analyzed a cohort of 676 patients (3DCRT=413, IMRT=263) treated with chemoradiation with or without surgery between 1998-2008. To correct for potential bias inherent in observational studies, we employed inverse probability of treatment weighted (IPW) methods based on propensity scores. Treatment probabilities (propensity scores) were estimated using logistic regression. Results: IMRT patients were less likely to receive induction chemotherapy and had poorer performance status. A fitted multivariate IPW-adjusted Cox model showed that overall survival was significantly associated with age, KPS, having surgery, tumor location, stage, having PET for staging, and radiation modality. Compared to IMRT, 3DCRT patients had a significantly greater risk of dying (72.6% vs 52.9%, IPW log rank test: p<0.0001) and for local-regional recurrence (LRR) (p=0.0038). The improvement in LRR was only apparent in the non-surgically treated patients due to better tumor control in the primary site, but not in the recurrence in regional nodal sites. There was no difference in cancer-specific mortality, distant metastasis, or postoperative deaths between the two groups. An increased cumulative incidence of cardiac deaths was seen in the 3DCRT group (p=0.049), but the cause of most deaths were unknown (5 year estimate: 11.7% in 3DCRT vs 5.4% in IMRT, Gray’s test, p=0.0029). Analyses using propensity score as a covariate gave very similar results. Conclusions: Our results indicate IMRT improves treatment outcomes in the management of esophageal cancer when compared to 3DCRT. These results, while retrospective, support the use of IMRT for the treatment of esophageal cancer.

A case of sinonasal teratocarcinosarcoma treated with surgery and post-operative intensity-modulated radiotherapy (IMRT)

Sinonasal teratocarcinosarcoma (SNTCS) is a rare and aggressive malignant neoplasm, which has poor prognosis. SNTCS is histologically characterized by the combination of one or more epithelial elements and mesenchymal components. We report a 59-year-old man with SNTCS involving right maxillary and ethmoid sinuses. He complained of numbness of the right cheek for 1 month. Computed tomography and magnetic resonance imaging revealed soft tissue filling the right maxillary and ethmoid sinuses, protruding into the nasal cavity. Tumor was removed with Denker rhinotomy, and post-operative intensity-modulated radiation therapy (IMRT: 64Gy in 32 fractions) was performed. Follow-up examination for 2 years after the IMRT has shown no evidence of recurrence or metastasis. IMRT is a new type of conformal radiotherapy that is based on the use of non-uniform radiation beam intensities. IMRT can achieve optimal dose distributions and may improve the clinical outcomes dramatically with minimal complications. This report describes this patient's clinical course, etiology, diagnosis and management of SNTCS, and the advantage of IMRT in the treatment of SNTCS.

Intensity Modulated Radiation Therapy (IMRT) in the Treatment of Squamous Carcinoma of the Oropharynx: An Overview

Background: Intensity Modulated Radiotherapy (IMRT) is being used increasingly for the radical treatment of oropharyngeal cancers. We have reviewed the evidence and summarised the data to enable readers to decide whether the dosimetric advantages of IMRT have been translated into clinical benefit in oropharyngeal cancer treatment. Methods: We searched Medline and the Cochrane library for published studies investigating the role of IMRT in reducing rates of xerostomia, osteoradionecrosis and difficulties with swallowing. Results: Despite heterogeneity in the assessment of xerostomia following radiotherapy, 20 out of the 22 studies reported lower xerostomia rates following parotid-sparing IMRT. There is only limited information on the consequences of sparing dose to the submandibular gland and emerging clinical information on the benefits of reducing dose to the pharyngeal constrictor muscles. Rates of osteoradionecrosis are lower with IMRT. Conclusion: Rates of xerostomia are lower with IMRT than with conventional radiotherapy techniques. Prospective evaluation of IMRT techniques to assess whether lower doses to the submandibular glands and constrictor muscles are associated with clinical benefit is essential. Although there appear to be lower rates of osteonecrosis with IMRT, pre treatment evaluation of dental status and maintenance of dental hygiene remain important.

Potential for dose escalation in the postprostatectomy setting with intensity-modulated radiation therapy: a dosimetric study using EORTC consensus guidelines for target volume contours

PurposeRadiation therapy (RT) is delivered as adjuvant and salvage therapy after radical prostatectomy for prostate cancer. Interest in dose escalation in this setting may necessitate more advanced RT techniques, such as intensity modulation. This study was designed to compare intensity-modulated radiation therapy (IMRT) versus 3-dimensional conformal radiation therapy (3DCRT) planning. MethodsTwenty patients were identified who received post--radical prostatectomy RT with 4-field, 3DCRT plans to 68.4 Gy. Contours were revised to comply with the European Organization for Research and Treatment of Cancer consensus guidelines. The IMRT plans with 5 versus 9 coplanar fields were compared for 10 patients. Then the 9-field IMRT plans were compared to 3DCRT in all 20 patients. Differences in dose-volume histogram values were evaluated using 2-tailed paired t tests. Cone beam computed tomographic images were analyzed to evaluate rectum doses in the treatment position during the RT course. The IMRT plans to 72.0 Gy were compared to 3DCRT to 68.4 Gy to be able to consider potential use in dose escalation. ResultsThe 9-field IMRT plans (vs 3DCRT) improved bladder mean dose and volume receiving 65 Gy or more (V65), as well as rectum mean dose (31.6 Gy vs 36.1 Gy; P < .001), volume receiving 75% or more of the prescription dose (24.4% vs 31.0%; P < .001), and V65 (10.5% vs 20.0%; P < .001). Advantages of IMRT were at the cost of small increases in maximum point doses delivered to the bladder and rectum. Cone beam computed tomographic images (n = 132) were analyzed for 8 patients; rectum mean dose and V65 were also improved by IMRT on these scans. IMRT allowed increasing dose to 72.0 Gy with similar bladder and rectum mean doses, V65, and V40 compared to 3DCRT to a total dose of 68.4 Gy. ConclusionsThe IMRT improves dosimetric parameters for the rectum and bladder, which may allow dose escalation after radical prostatectomy. Future studies should determine whether these advantages translate into improved clinical outcomes for prostate cancer patients.

Dosimetry of conformal dynamic arc radiotherapy and intensity modulated radiotherapy in unresectable cholangiocarcinoma

Abstract Background: Radiotherapy in cholangiocrcinoma has to overcome organ tolerance of the upper abdomen. Hi-technology radiotherapy may improve conformity and reduce dose to those organ. Objective: Quantitatively compare the dosimetry of conformal dynamic arc radiotherapy (CD-arcRT) and intensity modulated radiotherapy (IMRT) in unresectable cholangiocarcinoma. Material and methods: Eleven cases of unresectable cholangiocarcinoma were re-planned with IMRT and CDarcRT at King Chulalongkhorn Memorial Hospital between 20 September 2004 and 31 December 2005. Both the planning techniques were evaluated using the dose volume histogram of the planning target volume and organ at risk. The conformation number and dose to critical normal structures were used to determine the techniques. Results: IMRT technique was significantly conformed to the planning target volume than CD-arcRT in term of conformation number. For critical structure, IMRT significantly reduced the radiation dose to liver in terms of mean liver dose, V30Gy and V20Gy of the right kidney. Conclusion: The advantage of IMRT was more conformity and reduced dose to critical structure compared with CD-arcRT, but there was no difference between these techniques in terms of V20Gy of left kidney and maximum dose to the spinal cord.

Dosimetric comparison between intensity-modulated radiotherapy and conformal radiotherapy for upper thoracic esophageal carcinoma

Treatment planning for radiotherapy of upper thoracic esophageal carcinoma is challenging due to the anatomical features. The difficulty may be resolved by intensity-modulated radiotherapy (IMRT). This study was to compare the dosimetric advantages of IMRT to that of conformal radiotherapy (CRT) for upper thoracic esophageal carcinoma, and to explore the clinical application of IMRT. Eleven patients with upper thoracic esophageal carcinoma were enrolled. In addition to the actually used CRT plan, a five-field IMRT plan was generated for each case. The parameters of dose volume histogram for targets and organs at risk were compared between two techniques. For the planning target volume (PTV) of tumor and para-tumor tissues, the mean dose, maximal dose, doses covering 99% and 95% volume were similar in IMRT and CRT plans (P>0.05). However, IMRT plan had a higher conformity index than CRT plan (0.68+/-0.04 vs. 0.46+/-0.11, P<0.01). For the PTV of supraclavicular region, IMRT plan showed a better dose heterogeneity index than CRT plan (1.17+/-0.05 vs. 1.33+/-0.15, P=0.01). IMRT plan had lower maximal dose to the planning risk volume of the spinal cord (44.4 Gy vs. 52.5 Gy, P<0.05) and lower lung volume received dose of 10 Gy or higher [(32+/-6)% vs. (35+/-9)%, P<0.05] than CRT plan. For the upper thoracic esophageal carcinoma, IMRT has more conformal distribution of dose and better spinal cord sparing than CRT, and can reduce the volume of lung that received dose of 10 Gy or higher.

Indications for tomotherapy/intensity-modulated radiation therapy in paediatric radiotherapy: extracranial disease

The potential conformality advantages of intensity-modulated radiation therapy (IMRT; TomoTherapy Hi Art system) over conventional linear accelerator based therapy was assessed in six consecutive children referred for extracranial radiotherapy. IMRT/tomotherapy was considered advantageous for (i) small abdominal tumours, compared with parallel opposed or single portal technology using a conventional linear accelerator, and (ii) re-treatment of an ethmoidal sarcoma, but not for palliation of a small spinal metastasis, or therapy for a whole deep cervical node chain or a pelvic side wall tumour in a young child. Considerations integral to the treatment decision included target volume dose conformality, "low-dose bath" effects (oncogenic and late growth sequelae) and treatment delivery time. IMRT/tomotherapy was the selected modality for therapy when the conformality advantages were perceived to outweigh any disadvantages in three out of the six cases. The dose conformality advantages of IMRT/tomotherapy are sufficient to selectively recommend its availability to the paediatric practice in accordance to the following criteria: (i) where conformality of radiation therapy to the target/tumour is critical and where the margin of safety (from gross/clinical target volume to planning target volume (PTV)) around the tumour is narrow; (ii) where adjacent organs at risk of radiation damage have a low threshold for damage; and (iii) where the "low-dose bath" phenomenon, which occurs between the upper and lower axial limits of the PTV, is not sufficiently disadvantageous (with regard to late oncogenesis or growth retardation) to outweigh the more confined (non-tumour) integral doses received in higher dose corridors through the body when utilizing conventional radiation techniques.

Solitary Extramedullary Plasmacytoma in the Oropharynx: Advantages of Intensity-Modulated Radiation Therapy

We report a case of a 59-year-old man with solitary extramedullary plasmacytoma in his oropharynx. Because the diagnosis is rare and there is only limited experience in the literature based on retrospective data, the optimal planning target volume and optimal dose of radiation therapy (RT) are still controversial. The frequently discussed problem is the necessity of first echelon lymph node irradiation because it is associated with a higher rate of complications such as xerostomia caused by damage to salivary glands. In order to prevent late toxicity, intensity-modulated RT with the use of simultaneous integrated boost and parotid salivary gland sparing was used in this patient's treatment. The RT was performed in 23 identical fractions, the primary tumor region was irradiated with a dose of 46 Gy and the first echelon lymph node region with the risk of subclinical disease with a dose of 41.4 Gy; the dose per fraction was 2 Gy and 1.8 Gy, respectively. The patient is alive and well > 20 months after the irradiation, without any evidence of disease. Parotid gland function remained intact, and no xerostomia occurred. This is the first report of the use of intensity-modulated RT with parotid gland sparing in the treatment of solitary extramedullary plasmacytoma in the head and neck region.

O18 Improvement of saliva production in ENT cancer patients treated by IMRT

Intensity modulated radiotherapy (IMRT) is a conformal radiotherapy that produces concave and irregular target volume dose distributions. IMRT has a potential to reduce the volume of healthy tissue irradiated to a high dose, but this often at the price of an increased volume of normal tissue irradiated to a low dose. Clinical benefits of IMRT are expected to be most pronounced at the body sites where sensitive normal tissues surround or are located next to a target with a complex 3D shape. The irradiation doses needed for tumor control are often markedly higher than the tolerance of the radiation sensitive structures such as the spinal cord, the optic nerves, the eyes, or the salivary glands in the treatment of head and neck cancer. Parotid gland salivary flow is markedly reduced following a cumulative dose of 30 50 Gy given with conventional fractionation and xerostomia may be prevented in most patients using a conformal parotid-sparing radiotherapy technique. However, in cohort studies where IMRT was compared with conventional and conformal radiotherapy techniques in the treatment of laryngeal or oropharyngeal carcinoma, the dosimetric advantage of IMRT translated into a reduction of late salivary toxicity with no apparent adverse impact on the tumor control. IMRT might reduce the radiation dose to the major salivary glands and the risk of permanent xerostomia without compromizing the likelihood for cure. Alternatively, IMRT might allow the target dose escalation at a given level of normal tissue damage. We describe here the clinical results on postirradiation salivary gland function in head and neck cancer patients treated with IMRT, and the technical aspects of IMRT applied. The results suggest that the major salivary gland function can be maintained with IMRT without a need to compromise the clinical target volume dose, or the locoregional control.

Potential Advantages of Intensity-Modulated Radiation Therapy in Gynecologic Malignancies

Radiation therapy (RT) plays a critical role in the management of gynecologic malignancies. Conventional RT may treat a large amount of normal tissue, which results in increased toxicities and a limitation on total dose. Intensity-modulated radiation therapy (IMRT) helps reduce the dose to normal tissue while delivering a higher dose to the tissues with microscopic or gross disease. This may have a potential benefit in the treatment of gynecologic malignancies especially in difficult cases such as grossly positive nodes, recurrent disease, and vulvar cancer. However, there is very little clinical data and very little experience with the use of IMRT in gynecologic malignancies. Therefore, before complete acceptance of IMRT in the treatment of gynecologic malignancies, large multicenter trials are needed to help develop guidelines and standards.

Intensity-modulated radiation therapy for head and neck cancer

Radiotherapy planning studies have confirmed dosimetric advantages of intensity-modulated radiation therapy over conventional and conformal radiation therapy. Utilization of intensity-modulated radiation therapy is ideal in head and neck cancer patients. Critical structures can be spared due to sharp dose gradients and limited organ motion with correct immobilization. Initial clinical results have shown excellent locoregional control, in part due to the delivery of high doses to the target volume. Reductions in acute toxicities and xerostomia through parotid sparing have been notable benefits. However, long-term outcomes with regards to local control and late toxicities with intensity-modulated radiation therapy are still lacking. This review focuses on the implementation of intensity-modulated radiation therapy for the treatment of head and neck cancers, with a specific focus on set-up uncertainties, dose prescription and target volume determination and delineation.

Intensity-modulated radiation therapy in the treatment of children

Intensity-modulated radiation therapy (IMRT) is a relatively new method of conformal radiotherapy delivery that is rapidly being incorporated in clinical practice. Of all patients treated with conformal techniques, children are the most likely to benefit as normal, developing structures can be minimized in the radiation field. The advantages of IMRT, including increased conformality and possible dose escalation, are discussed in this review. Possible disadvantages of IMRT in children are also discussed, such as lack of dose homogeneity in the target volume, increased dose to nontarget tissues, reliability of treatment setup, increased anesthesia time in younger children, and prolonged treatment planning. The issue of increased risk of second malignancy in this very young population is important, as many of these children will be long-term survivors with current multimodality therapy.

Individualizing cancer treatment: biological optimization models in treatment planning and delivery

Purpose: During the last 30 years radiation therapy has developed from classical rectangular beams via conformation therapy with largely uniform dose delivery, but irregular field shapes, to fully intensity modulated dose delivery where the total dose distribution in the tumor can be fully controlled in three dimensions. This last step has been developed during the last 15–20 years and has opened up the possibilities for truly optimized radiation therapy. Methods and Materials: Today it is not only possible to produce almost any desired dose distribution in the tumor volume. It is also possible to deliver the dose distribution, which has the highest probability to cure the patient without inducing severe complications in normal tissues. To fully exploit the advantages of intensity-modulated radiation therapy, quality of life or radiobiologic objectives have to be used, preferably combined with predictive assay of radiation sensitivity. Results: This article will briefly discuss the biologic objective functions and the associated advantages in the treatment outcome using new approaches such as consideration of stochastic variations in sensitivity and optimization of the angle of incidence and fractionation schedule with intensity-modulated beams. Finally, different possibilities for realizing general three-dimensional intensity-modulated dose delivery will be discussed. Conclusions: Once accurate genetically and/or cell survival based predictive assays become available, radiation therapy will become an exact science allowing truly individual optimization considering also the panorama of side-effects that the patient is willing to accept.