Systematic dosimetric evaluation of risk of osteoradionecrosis (DERO): First results of dose reporting for preventing teeth osteoradionecrosis after head and neck irradiation

PurposeOsteoRadioNecrosis (ORN) is a late complication of radiation for head and neck cancer. Predicting ORN is a major challenge. We developed DERO (Dosimetric Evaluation of Risk of ORN), a semi-automatic tool which reports doses delivered to tooth-bearing sectors, to guide post-therapeutic dental care. We present the method and the first results of a 125-patient prospective cohort.Material and methodsDosimetric data of patients treated with IMRT for head and neck cancer were prospectively segmented to the DERO algorithm. Four arches corresponding to 8-tooth sectors were semi-automatically generated. Thirty-two cylindrical Regions Of Interest (ROI) corresponding to each tooth and surrounding periodontium were created by linear interpolation. Mean doses (Dmean) of ROI were extracted and included in a database, along with data about primary tumor site, laterality and dose values from organs at risk. Dmean to tooth sectors were computed for molar sectors, (teeth X5 to X8) and anterior sectors (teeth X1 to X4). An individual dose map was generated and delivered to patients and dentists.ResultsDosimetric data from 125 patients treated with Tomotherapy® were prospectively collected and analyzed: 9 parotid tumors (PA), 41 Sub-Hyoid tumors (larynx, hypopharynx) (SH), 43 Oropharynx tumors (OR), 32 Oral Cavity tumors (OC). Irradiation was unilateral for 100% of PA tumors (9), 12% of OR tumors (5) and 47% of OC tumors (15). For unilateral cervical irradiation, Dmean in ipsilateral molar sectors was 54 Gy for OC tumors, 45 Gy for OR tumors, 20 Gy for PA tumors. For Oral Cavity bilateral irradiation, Dmean was high in all tooth sectors, 49 to 55 Gy. For SH tumors, Dmean in molar sectors was 27 Gy. A dose gradient of 10 to 20 Gy was observed between molar and anterior sectors whether radiation was uni or bilateral.ConclusionMandibular molar sectors of Oropharynx and Oral Cavity tumors were exposed to high Dmean of 40 to 50 Gy. On the other hand, tooth sectors received lower doses for SH radiation. The DERO tool guide post-radiation dental care with a personalized dosimetric cartography to patient. With data update and patient follow-up, we will be able to determine ORN risk after head and neck radiation.     

Facteurs prédictifs de l’ostéoradionécrose mandibulaire après irradiation des cancers des voies aérodigestives supérieures

The identification of the different risk factors for mandibular osteoradionecrosis (ORN) must be done before and after the management of patients with head and neck cancer. Various clinical criteria for this severe radiation-induced complication are related to the patient (intrinsic radiosensitivity, malnutrition associated with thin weight loss, active smoking intoxication, microcapillary involvement, precarious oral status, hyposalivation) and/or related to the disease (oral cavity, large tumor size, tumor mandibular invasion). Therapeutic risk factors are also associated with a higher risk of ORN (primary tumor surgery, concomitant radio-chemotherapy, post-irradiation dental avulsion, preventive non-observance with the absence of stomatological follow-up and daily installation of gutters fluoride and, non-observance curative healing treatments). Finally, various dosimetric studies have specified the parameters in order to target the dose values distributed in the mandible, which increases the risk of ORN. An mean mandibular dose greater than 48–54 Gy and high percentages of mandibular volume receiving 40 to 60 Gy appear to be discriminating in the risk of developing an ORN.     

Osteoradionecrosis prevention myths

PURPOSE: To critically analyze controversial osteoradionecrosis (ORN) prevention techniques, including preradiation extractions of healthy or restorable teeth and the use of prophylactic antibiotics or hyperbaric oxygen (HBO) treatments for preradiation and postradiation extractions. METHODS: The author reviewed ORN studies found on PubMed and in other article references, including studies on overall ORN incidence and pre- and postradiation incidence, with and without prophylactic HBO or antibiotics. RESULTS: Owing in part to more efficient radiation techniques, the incidence of ORN has been declining in radiation patients over the last 2 decades, but the prevention of ORN remains controversial. A review of the available literature does not support the preradiation extraction of restorable or healthy teeth. There is also insufficient evidence to support the use of prophylactic HBO treatments or prophylactic antibiotics before extractions or other oral surgical procedures in radiation patients. CONCLUSIONS: To prevent ORN, irradiated dental patients should maintain a high level of oral health. A preradiation referral for a dental evaluation and close collaboration by a multidisciplinary team can be invaluable for radiation patients. As with most other dental patients, restorable and healthy teeth should be retained in irradiated patients. The use of prophylactic HBO or antibiotics should be reconsidered for preradiation and postradiation extractions.     

Intensity-modulated radiotherapy in nasopharyngeal carcinoma: dosimetric advantage over conventional plans and feasibility of dose escalation

PURPOSE: To compare intensity-modulated radiotherapy (IMRT) with two-dimensional RT (2D-RT) and three-dimensional conformal radiotherapy (3D-CRT) treatment plans in different stages of nasopharyngeal carcinoma and to explore the feasibility of dose escalation in locally advanced disease. MATERIALS AND METHODS: Three patients with different stages (T1N0M0, T2bN2M0 with retrostyloid extension, and T4N2M0) were selected, and 2D-RT, 3D-CRT, and IMRT treatment plans (66 Gy) were made for each of them and compared with respect to target coverage, normal tissue sparing, and tumor control probability/normal tissue complication probability values. In the Stage T2b and T4 patients, the IMRT 66-Gy plan was combined with a 3D-CRT 14-Gy boost plan using a 3-mm micromultileaf collimator, and the dose-volume histograms of the summed plans were compared with their corresponding 66-Gy 2D-RT plans. RESULTS: In the dosimetric comparison of 2D-RT, 3D-CRT, and IMRT treatment plans, the T1N0M0 patient had better sparing of the parotid glands and temporomandibular joints with IMRT (dose to 50% parotid volume, 57 Gy, 50 Gy, and 31 Gy, respectively). In the T2bN2M0 patient, the dose to 95% volume of the planning target volume improved from 57.5 Gy in 2D-RT to 64.8 Gy in 3D-CRT and 68 Gy in IMRT. In the T4N2M0 patient, improvement in both target coverage and brainstem/temporal lobe sparing was seen with IMRT planning. In the dose-escalation study for locally advanced disease, IMRT 66 Gy plus 14 Gy 3D-CRT boost achieved an improvement in the therapeutic ratio by delivering a higher dose to the target while keeping the normal organs below the maximal tolerance dose. CONCLUSIONS: IMRT is useful in treating all stages of nonmetastatic nasopharyngeal carcinoma because of its dosimetric advantages. In early-stage disease, it provides better parotid gland sparing. In locally advanced disease, IMRT offers better tumor coverage and normal organ sparing and allows room for dose escalation.     

Dose Planning Study of Target Volume Coverage with Intensity-Modulated Radiotherapy for Nasopharyngeal Carcinoma: Penang General Hospital Experience

Background: To compare the dosimetric coverage of target volumes and organs at risk in the radicaltreatment of nasopharyngeal carcinoma (NPC) between intensity-modulated radiotherapy (IMRT) and threedimensionalconformal radiotherapy (3DCRT). Materials and Methods: Data from 10 consecutive patientstreated with IMRT from June-October 2011 in Penang General Hospital were collected retrospectively foranalysis. For each patient, dose volume histograms were generated for both the IMRT and 3DCRT plans usinga total dose of 70Gy. Comparison of the plans was accomplished by comparing the target volume coverage (5measures) and sparing of organs at risk (17 organs) for each patient using both IMRT and 3DCRT. The meansof each comparison target volume coverage measures and organs at risk measures were obtained and testedfor statistical significance using the paired Student t-test. Results: All 5 measures for target volume coverageshowed marked dosimetric superiority of IMRT over 3DCRT. V70 and V66.5 for PTV70 showed an absoluteimprovement of 39.3% and 24.1% respectively. V59.4 and V56.4 for PTV59.4 showed advantages of 18.4% and16.4%. Moreover, the mean PTV70 dose revealed a 5.1 Gy higher dose with IMRT. Only 4 out of 17 organsat risk showed statistically significant difference in their means which were clinically meaningful between theIMRT and 3DCRT techniques. IMRT was superior in sparing the spinal cord (less 5.8Gy), V30 of right parotid(less 14.3%) and V30 of the left parotid (less 13.1%). The V55 of the left cochlea was lower with 3DCRT (less44.3%). Conclusions: IMRT is superior to 3DCRT due to its dosimetric advantage in target volume coveragewhile delivering acceptable doses to organs at risk. A total dose of 70Gy with IMRT should be considered as astandard of care for radical treatment of NPC.     

Geometric factors influencing dosimetric sparing of the parotid glands using IMRT

PURPOSE/OBJECTIVE: To determine the relationship between the parotid volume, parotid-planning target volume (PTV) overlap, and dosimetric sparing of the parotid with intensity-modulated radiation therapy (IMRT). METHODS AND MATERIALS: Parotid data were collected retrospectively for 51 patients treated with simultaneous boost IMRT. Unresectable patients received 54 or 59.4 Gy to subclinical disease, 70 Gy to gross disease. Patients treated postoperatively received 54, 60, and 66 Gy to low-risk, high-risk, and tumor bed regions. Volume and mean dose of each gland and gland segments outside of and overlapping the PTV were collected. Proximity of each gland to each PTV was recorded. RESULTS: Dosimetric sparing (mean dose 21% overlap (p = <0.0001). Among spared glands, the median mean dose in the overlap region was 55.0 Gy in glands with < or =21% overlap, but only 45.4 Gy when overlap >21%. Median mean dose was 25.9 Gy to glands overlapping PTV(54) or PTV(59) alone and 30.0 Gy to those abutting PTV(70) (p < 0.001). Although proximity to PTV(70) was associated with higher parotid dose, satisfactory sparing was achieved in 24 of 43 ipsilateral glands. CONCLUSIONS: Dosimetric sparing of the parotid is feasible when the parotid-PTV overlap is less than approximately 20%. With more overlap, sparing may result in low doses within the overlap region, possibly leading to inadequate PTV coverage. Gland proximity to the high-dose PTV is associated with higher mean dose but does not always preclude dosimetric sparing.     

Parotid-sparing intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma: preserved parotid function after IMRT on quantitative salivary scintigraphy, and comparison with historical data after conventional radiotherapy

PURPOSE: To evaluate the parotid function after parotid-sparing intensity-modulated radiotherapy (IMRT) in patients with nasopharyngeal carcinoma (NPC). METHODS AND MATERIALS: From March 2003 to May 2004, 16 patients with nonmetastatic NPC underwent parotid-sparing IMRT. Eight of these patients had Stage III or IV NPC based on the 1997 American Joint Committee on Cancer staging system. The post-IMRT parotid function was evaluated by quantitative salivary scintigraphy and represented by the maximal excretion ratio (MER) of the parotid gland after sialogogue stimulation. The parotid function of 16 NPC patients who were previously treated with conventional radiotherapy was reviewed as the historical control. RESULTS: In the parotid-sparing IMRT group, all 16 patients were alive and without cancer at the end of follow-up period (median, 24.2 months). The mean parotid MER was 53.5% before radiotherapy, 10.7% at 1 month post-IMRT, and 23.3% at 9 months post-IMRT. In the conventional radiotherapy group, the mean parotid MER was 0.6% at 6 to 12 months postradiotherapy. The difference was statistically significant (23.3% vs. 0.6%, p<0.001, Mann-Whitney test). In the IMRT group, the mean parotid doses ranged from 33.2 Gy to 58.8 Gy (average, 43.9 Gy). The correlation between the mean parotid dose and the percentage decrease of parotid MER at 9 months post-IMRT (dMER) was statically significant (p=0.008, Pearson correlation). CONCLUSIONS: Although the mean parotid doses are relatively high, the significant preservation of parotid function is achieved with IMRT for NPC patients. The significant correlation between mean parotid dose and parotid dMER demonstrates the dose-function relationship of the parotid gland.     

Intensity-modulated radiotherapy for early-stage nasopharyngeal carcinoma: a prospective study on disease control and preservation of salivary function

BACKGROUND: Xerostomia is a uniform complication after radiotherapy (RT) for nasopharyngeal carcinoma (NPC). Dosimetric studies suggested that intensity-modulated RT (IMRT) can spare part of the parotid glands from high-dose radiation. Disease control and salivary function after IMRT for early-stage NPC was studied prospectively. METHODS: Thirty-three patients with T1,N0-N1,M0 NPC were treated with IMRT from 2000 to 2002. The prescribed dose was 68-70 grays (Gy) in 34 fractions to gross tumor volume, 64-68 Gy to the planning target volume, and 70 Gy to enlarged cervical lymph nodes. Nineteen patients had stimulated whole salivary (SWS) flow assessment and stimulated parotid salivary (SPS) flow assessment at baseline and at 2 months, 6 months, 12 months, 18 months, and 24 months after the completion of IMRT. RESULTS: At a median follow-up of 2 years, only 1 neck failure was observed. The 2-year and 3-year local control, distant metastases-free, and overall survival rates all were 100%. The lymph node control and progression-free survival rates were 100% at 2 years and 92.3% at 3 years, respectively. The average mean dose to the parotid gland was 38.8 Gy. The SWS and SPS flow showed continuous recovery: 60% and 47.1% of patients recovered at least 25% of their baseline SPS flow and SWS flow, respectively, at 1 year after completion of IMRT, and the proportions rose to 85.7% and 71.4%, respectively, by 2 years. The pH and buffering capacity of saliva also improved with time. CONCLUSIONS: Parotid-sparing IMRT achieved good locoregional control, and there was continuous recovery of salivary flow, pH, and buffering capacity in the first 2 years after IMRT in patients with NPC.     

Extra-mandibular Osteoradionecrosis after the Treatment of Head and Neck Cancer

AimsOsteoradionecrosis (ORN) is a serious toxicity of head and neck radiotherapy. It predominantly affects the mandible. Extra-mandibular ORN is rare. The aim of this study was to report the incidence and outcomes of extra-mandibular ORNs from a large institutional database.Materials and methodsIn total, 2303 head and neck cancer patients were treated with radical or adjuvant radiotherapy. Of these, extra-mandibular ORN developed in 13 patients (0.5%).ResultsMaxillary ORNs (n = 8) were a consequence of the treatment of various primaries (oropharynx = 3, sinonasal = 2, maxilla = 2, parotid = 1). The median interval from the end of radiotherapy to the development of ORN was 7.5 months (range 3–42 months). The median radiotherapy dose in the centre of the ORN was 48.5 Gy (range 22–66.5 Gy). Four patients (50%) healed in 7, 14, 20 and 41 months.All temporal bone ORNs (n = 5) developed after treatment to the parotid gland (of a total of 115 patients who received radiotherapy for parotid gland malignancy). The median interval from the end of radiotherapy to the development of ORN was 41 months (range 20–68 months). The median total dose in the centre of the ORN was 63.5 Gy (range 60.2–65.3 Gy). ORN healed in only one patient after 32 months of treatment with repeated debridement and topical betamethasone cream.ConclusionExtra-mandibular ORN is a rare late toxicity and this current study provides useful information on its incidence and outcome. The risk of temporal bone ORN should be considered in the treatment of parotid malignancies and patients should be counselled. More research is required to determine the optimal management of extra-mandibular ORN, particularly on the role of the PENTOCLO regimen.     

Treatment planning and delivery of intensity-modulated radiation therapy for primary nasopharynx cancer

PURPOSE: To implement intensity-modulated radiation therapy (IMRT) for primary nasopharynx cancer and to compare this technique with conventional treatment methods. METHODS AND MATERIALS: Between May 1998 and June 2000, 23 patients with primary nasopharynx cancer were treated with IMRT delivered with dynamic multileaf collimation. Treatments were designed using an inverse planning algorithm, which accepts dose and dose-volume constraints for targets and normal structures. The IMRT plan was compared with a traditional plan consisting of phased lateral fields and a three-dimensional (3D) plan consisting of a combination of lateral fields and a 3D conformal plan. RESULTS: Mean planning target volume (PTV) dose increased from 67.9 Gy with the traditional plan, to 74.6 Gy and 77.3 Gy with the 3D and IMRT plans, respectively. PTV coverage improved in the parapharyngeal region, the skull base, and the medial aspects of the nodal volumes using IMRT and doses to all normal structures decreased compared to the other treatment approaches. Average maximum cord dose decreased from 49 Gy with the traditional plan, to 44 Gy with the 3D plan and 34.5 Gy with IMRT. With the IMRT plan, the volume of mandible and temporal lobes receiving more than 60 Gy decreased by 10-15% compared to the traditional and 3D plans. The mean parotid gland dose decreased with IMRT, although it was not low enough to preserve salivary function. CONCLUSION: Lower normal tissue doses and improved target coverage, primarily in the retropharynx, skull base, and nodal regions, were achieved using IMRT. IMRT could potentially improve locoregional control and toxicity at current dose levels or facilitate dose escalation to further enhance locoregional control.     

Dose and volume reduction for normal lung using intensity-modulated radiotherapy for advanced-stage non-small-cell lung cancer

PURPOSE: To investigate dosimetric improvements with respect to tumor-dose conformity and normal tissue sparing using intensity-modulated radiotherapy (IMRT) compared with three-dimensional conformal radiotherapy (3D-CRT) for advanced-stage non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: Forty-one patients with Stage III-IV and recurrent NSCLC who previously underwent 3D-CRT were included. IMRT plans were designed to deliver 63 Gy to 95% of the planning target volume using nine equidistant coplanar 6-MV beams. Inverse planning was performed to minimize the volumes of normal lung, heart, esophagus, and spinal cord irradiated above their tolerance doses. Dose distributions and dosimetric indexes for the tumors and critical structures in both plans were computed and compared. RESULTS: Using IMRT, the median absolute reduction in the percentage of lung volume irradiated to >10 and >20 Gy was 7% and 10%, respectively. This corresponded to a decrease of >2 Gy in the total lung mean dose and of 10% in the risk of radiation pneumonitis. The volumes of the heart and esophagus irradiated to >40-50 Gy and normal thoracic tissue volume irradiated to >10-40 Gy were reduced using the IMRT plans. A marginal increase occurred in the spinal cord maximal dose and lung volume >5 Gy in the IMRT plans, which could be have resulted from the significant increase in monitor units and thus leakage dose in IMRT. CONCLUSION: IMRT planning significantly improved target coverage and reduced the volume of normal lung irradiated above low doses. The spread of low doses to normal tissues can be controlled in IMRT with appropriately selected planning parameters. The dosimetric benefits of IMRT for advanced-stage non-small-cell lung cancer must be evaluated further in clinical trials.     

Disease-control rates following intensity-modulated radiation therapy for small primary oropharyngeal carcinoma

BACKGROUND: The purpose of this study was to assess the ability of intensity-modulated radiation therapy (IMRT) to achieve favorable disease-control rates while minimizing parotid gland doses in patients treated for small primary tumors of the oropharynx. METHODS AND MATERIALS: We retrospectively identified all patients who received IMRT as treatment for a small (<4 cm) primary tumor of the oropharynx between October 2000 and June 2002. Tumor characteristics, IMRT parameters, and patient outcomes were assessed. RESULTS: Fifty-one patients met the criteria for our study. All patients had treatment to gross disease with margin (CTV1), and all but 1 had treatment to the bilateral necks. The most common treatment schedule (39 patients) was a once-daily fractionation of prescribed doses of 63-66 Gy to the CTV1 and 54 Gy to subclinical sites, delivered in 30 fractions. Twenty-one patients (40%) had gastrostomy tubes placed during therapy; in 4 patients, the tube remained in place for more than 6 months after completion of IMRT. The median follow-up was 45 months. The 2-year actuarial locoregional control, recurrence-free, and overall survival rates were 94%, 88%, and 94%, respectively. CONCLUSIONS: These preliminary data suggest that treatment with IMRT results in favorable locoregional control of small primary oropharynx tumors. IMRT did not appear to have a more favorable acute toxicity profile in this group with respect to the use of a feeding tube; however, the mean dose of radiation delivered to the parotid gland by IMRT was decreased, because 95% of patients had a mean dose of <30 Gy to at least one gland.     

Initial evaluation of treatment-related pneumonitis in advanced-stage non-small-cell lung cancer patients treated with concurrent chemotherapy and intensity-modulated radiotherapy

PURPOSE: To investigate the rate of high-grade treatment-related pneumonitis (TRP) in patients with advanced non-small-cell lung cancer (NSCLC) treated with concurrent chemotherapy and intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS: From August 2002 to August 2005, 151 NSCLC patients were treated with IMRT. We excluded patients who did not receive concurrent chemotherapy or who had early-stage cancers, a history of major lung surgery, prior chest RT, a dose <50 Gy, or IMRT combined with three-dimensional conformal RT (3D-CRT). Toxicities were graded by Common Terminology Criteria for Adverse Events version 3.0. Grade > or = 3 TRP for 68 eligible IMRT patients was compared with TRP among 222 similar patients treated with 3D-CRT. RESULTS: The median follow-up durations for the IMRT and 3D-CRT patients were 8 months (range, 0-27 months) and 9 months (range, 0-56 months), respectively. The median IMRT and 3D-CRT doses were 63 Gy. The median gross tumor volume was 194 mL (range, 21-911 mL) for IMRT, compared with 142 mL (range, 1.5-1,186 mL) for 3D-CRT (p = 0.002). Despite the IMRT group's larger gross tumor volume, the rate of Grade > or = 3 TRP at 12 months was 8% (95% confidence interval 4%-19%), compared with 32% (95% confidence interval 26%-40%) for 3D-CRT (p = 0.002). CONCLUSIONS: In advanced NSCLC patients treated with chemoradiation, IMRT resulted in significantly lower levels of Grade > or = 3 TRP compared with 3D-CRT. Clinical, dosimetric, and patient selection factors that may have influenced rates of TRP require continuing investigation. A randomized trial comparing IMRT with 3D-CRT has been initiated.     

鼻咽癌调强放疗的剂量学研究

 【摘要】目的 分析鼻咽癌调强放疗各个靶区和周围正常组织器官的剂量学特点。方法 2005年1月-2006年6月住院的30例初治鼻咽癌进行调强放疗，将鼻咽和颈部的靶体积勾画为鼻咽大体肿瘤体积（GTVnx）、颈部大体肿瘤体积(GTVnd)、临床靶体积1（CTV1）和临床靶体积2(CTV2)，处方剂量分别为70、66、60、60Gy/30F，鼻咽和上颈部靶体积采用IMRT技术照射、下颈部靶体积采用下颈前野常规照射。研究GTV、CTV的最大、最小、平均剂量和颞叶、脑干、脊髓、视神经、晶体、眼球的最大受照剂量及腮腺、颞下颌关节的50%体积受照剂量。结果 GTVnx的最大、最小、平均剂量（均值）分别为79.2、59.5、71.9Gy, GTVnd的最大、最小、平均剂量分别为77.1、63.6、72.1Gy，CTV1、CTV2的最小剂量分别为47.6、49.7Gy，颞叶、脑干、脊髓、视神经、晶体、眼球的最大受照剂量及腮腺、颞下颌关节的50%体积受照剂量63.2、48.6、44.7、59.3、6.9、25.9Gy和34.0、36.3Gy。结论 调强放疗可以使各个靶区得到足够的、均匀的剂量分布，周围正常组织器官得到较好的保护，但是要注意CTV的低剂量区。鼻咽癌调强放疗剂量分布优于常规放疗。     

Combined photon and electron three-dimensional conformal versus intensity-modulated radiotherapy with integrated boost for adjuvant treatment of malignant pleural mesothelioma after pleuropneumonectomy

PURPOSE: The optimal technique for postoperative radiotherapy (RT) after extrapleural pleuropneumonectomy (EPP) of malignant pleural mesothelioma (MPM) remains debated. METHODS AND MATERIALS: The data from 8 right-sided and 9 left-sided consecutive cases of MPM treated with RT after radical EPP were reviewed. Of the 17 patients, 8 had been treated with three-dimensional (3D) conformal RT (3D-CRT) and 9 with intensity-modulated RT (IMRT) with 6-MV photons. The clinical outcome and adverse events were assessed. For comparative planning, each case was replanned with 3D-CRT using photons and electrons or with IMRT. Homogeneity, doses to the organs at risk, and target volume coverage were analyzed. RESULTS: Both techniques yielded acceptable plans. The dose coverage and homogeneity of IMRT increased by 7.7% for the first planning target volume and 9.7% for the second planning target volume, ensuring >or=95% of the prescribed dose compared with 3D-CRT (p < 0.01). Compared with 3D-CRT, IMRT increased the dose to the contralateral lung, with an increase in the mean lung dose of 7.8 Gy and an increase in the volume receiving 13 Gy and 20 Gy by 20.5% and 7.2%, respectively (p < 0.01). A negligible dose increase to the contralateral kidney and liver was observed. No differences were seen for the spinal cord and ipsilateral kidney. Two adverse events of clinical relevant lung toxicity were observed with IMRT. CONCLUSION: Intensity-modulated RT and 3D-CRT are both suitable for adjuvant RT. IMRT improves the planning target volume coverage but delivered greater doses to the organs at risk. Rigid dose constraints for the lung should be respected.     

The impact of dose escalation on secondary cancer risk after radiotherapy of prostate cancer

PURPOSE: To estimate secondary cancer risk due to dose escalation in patients treated for prostatic carcinoma with three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated RT (IMRT), and spot-scanned proton RT. METHODS AND MATERIALS: The organ equivalent dose (OED) concept with a linear-exponential, a plateau, and a linear dose-response curve was applied to dose distributions of 23 patients who received RT of prostate cancer. Conformal RT was used in 7 patients, 8 patients received IMRT with 6- and 15-MV photons, and 8 patients were treated with spot-scanned protons. We applied target doses ranging from 70 Gy to 100 Gy. Cancer risk was estimated as a function of target dose and tumor control probability. RESULTS: At a 100-Gy target dose the secondary cancer risk relative to the 3D treatment plan at 70 Gy was +18.4% (15.0% for a plateau model, 22.3% for a linear model) for the 6-MV IMRT plan, +25.3% (17.0%, 14.1%) for the 15-MV IMRT plan, and -40.7% (-41.3%, -40.0%) for the spot-scanned protons. The increasing risk of developing a radiation-associated malignancy after RT with increasing dose was balanced by the enhanced cure rates at a larger dose. CONCLUSIONS: Cancer risk after dose escalation for prostate RT is expected to be equal to or lower than for conventional 3D treatment at 70 Gy, independent of treatment modality or dose-response model. Spot-scanned protons are the treatment of choice for dose escalation because this therapy can halve the risk of secondary cancers.     

Potential outcomes of modalities and techniques in radiotherapy for patients with hypopharyngeal carcinoma.

BACKGROUND AND PURPOSE: To determine potential improvements in treatment outcome for patients with hypopharyngeal carcinoma, T4N0M0, using proton and intensity modulated photon radiotherapy (IMRT) compared to a standard 3D conformal radiotherapy treatment (3D-CRT) in terms of local tumour control probability, TCP, and normal tissue complication probability (NTCP) for the spinal cord and the parotid glands using. PATIENTS AND METHODS: Using the three-dimensional treatment-planning system, Helax-TMS, 5 patients were planned with protons, IMRT, and 3D-CRT plans. The prescribed dose used was 30 fractions x 2.39 Gy for the protons and IMRT and 35 fractions x 2.00 Gy for 3D-CRT. The treatment plans were evaluated using dose volume data and dose response models were used to calculate TCP and NTCP. The target volumes were delineated to spare the parotid glands. A dose escalation was made for protons and IMRT using NTCP constraints to the spinal cord. RESULTS: On average, protons and IMRT increase TCP by 17% compared to 3D-CRT. For the spinal cord NTCP values are zero for all methods and patients. Average NTCP values for the parotid glands were >90% for 3D-CRT and significantly lower for protons and IMRT varying from 43-65%. The average parotid gland dose was 33 Gy for the protons, 38 Gy for IMRT and 48 Gy for 3D-CRT. CONCLUSIONS: Protons and IMRT gave a significant TCP increase compared to 3D-CRT while no significant difference between protons and IMRT was found. Protons generally show lower non-target tissue doses, which indicates a possibility for further dose escalation. Large individual dose differences between protons and IMRT for parotid glands indicate that some patients may benefit more from protons and others from IMRT.