Incidental Dose Research Articles

Comparison of testicular dose delivered by intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in patients with prostate cancer

A small decrease in testosterone level has been documented after prostate irradiation, possibly owing to the incidental dose to the testes. Testicular doses from prostate external beam radiation plans with either intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) were calculated to investigate any difference. Testicles were contoured for 16 patients being treated for localized prostate cancer. For each patient, 2 plans were created: 1 with IMRT and 1 with VMAT. No specific attempt was made to reduce testicular dose. Minimum, maximum, and mean doses to the testicles were recorded for each plan. Of the 16 patients, 4 received a total dose of 7800cGy to the prostate alone, 7 received 8000cGy to the prostate alone, and 5 received 8000cGy to the prostate and pelvic lymph nodes. The mean (range) of testicular dose with an IMRT plan was 54.7cGy (21.1 to 91.9) and 59.0cGy (25.1 to 93.4) with a VMAT plan. In 12 cases, the mean VMAT dose was higher than the mean IMRT dose, with a mean difference of 4.3cGy (p = 0.019). There was a small but statistically significant increase in mean testicular dose delivered by VMAT compared with IMRT. Despite this, it unlikely that there is a clinically meaningful difference in testicular doses from either modality.

Cardiac avoidance in breast radiotherapy: many choices for a worthwhile objective.

In this Research Topic, Goyal and Haffty have collected a series of papers on the emerging field of cardio-oncology. Indeed, Darby et al.’s paper demonstrating an incremental 7% increase in risk of ischemic events per gray increase in mean heart dose has been a watershed moment in our efforts to improve the therapeutic ratio of adjuvant breast radiotherapy (1). While a 0.07 increase over baseline risk per Sievert may seem high, it is important to understand this relative increase in risk in the context of the absolute baseline risk. Darby and colleagues do not provide a denominator for eligible patients in the two population registries from which they drew their cases and controls. Instead, they estimate the baseline risk using data from 15 Western European nations, and in Table S12 of the Supplementary Material, go on to estimate the absolute risk increase by age 80 years in women exposed to RT at various ages and with various co-morbid risk profiles. The excess absolute risks appear to be modest at first glance. For example, for a young 40-year-old woman receiving a high mean heart dose of 10 Gy, the estimated absolute excess risk of dying from cardiac disease is about 1.4%. Should the same woman have at least one co-morbid risk factor, her excess risk is 2.3%. These numbers may seem small, but are certainly relevant at the population level, especially given that the mortality benefit of adjuvant radiotherapy is also modest (2). Current efforts at reducing the risks of incidental cardiac irradiation have included advanced radiotherapy techniques for cardiac avoidance such as breath hold (3), gating treatments (4), proton therapy (5), prone positioning (6), and combinations thereof such as respiratory gating in the prone position (7). Cardiac avoidance techniques are illustrative of the general potential that technological innovations can have on human health. Going back to the very development of megavoltage machines, improvements in radiation delivery have consistently improved the therapeutic ratio in any number of settings. Recent reports have demonstrated fewer late second malignancies in children treated with proton therapy (8), lower rates of desquamation in breast cancer patients treated with IMRT (9), higher rates of local control in lung cancer patients treated with SBRT (10), and improved biochemical control in patients treated with highly conformal, high-dose radiotherapy for prostate cancer (11). Similar improvements in image-guided gynecological brachytherapy (12), IMRT in head/neck (13), GI (14), and gynecological malignancies (15), as well as intracranial SRS (16) have all demonstrated better outcomes compared with control data. Even as the calls for controlling costs become ever more constant, it is important to remember that the current excitement for a genomically driven model of cancer care has become possible only because of technological improvements in sequencing technologies. As such, continued funding, both federal and private, for technology innovations is critical and should not be relegated to lower tiers of priority. Coming back to breast cancer patients and the cardiac risks they face from radiotherapy, one additional (seemingly obvious) point needs to be made. While we can invoke continually advancing technologies for the purposes of cardiac avoidance (17), sometimes a return to simpler solutions may be all that is needed. Many women with early-stage breast cancer are eligible for off-protocol accelerated partial breast irradiation as a standard of care option (18). As one would expect, irradiating a smaller volume of breast tissue leads to lower incidental heart doses (19). Current studies and protocols examining, for example, breath hold parameters or prone positioning often include a large contingent of women who are candidates for partial breast irradiation. One rather elegant way to avoid treating the heart is to simply not treat it.

Patterns of Regional Failure and Evaluation of LN Dose in Early-Stage NSCLC Treated With SBRT

SBRT is used for curative intent in medically inoperable early stage NSCLC with 4 year regional control rates of ∼80%. It is hypothesized that incidental low dose to regional lymph nodes (LN) may contribute to regional control. The purpose of this study is to test the hypothesis that incidental radiation dose to regional LNs affects regional control in SBRT for early stage NSCLC.

Coverage of Posterior Supraclavicular Fossa With Postmastectomy Proton Therapy for Breast Cancer: A Dosimetric Comparison Study and Implications for Target Definition

The posterior aspect of the supraclavicular fossa (SCF) is a known site of nodal metastases and failure in patients with locally advanced breast cancer, yet it is not included in the RTOG breast nodal atlas. With conventional techniques, this area often receives a large incidental dose even if not purposefully included in the target volume. However, the dose delivered to this area when treating with RTOG contouring atlas-specified proton therapy and other highly conformal external beam radiation modalities is not well described.

Incidental Prophylactic Nodal Irradiation and Patterns of Nodal Relapse in Inoperable Early Stage NSCLC Patients Treated With SBRT: A Case-Matched Analysis

Reported rates of non-small cell lung cancer (NSCLC) nodal failure following stereotactic body radiation therapy (SBRT) are lower than those reported in the surgical series when matched for stage. We hypothesized that this effect was due to incidental prophylactic nodal irradiation. A prospectively collected group of medically inoperable early stage NSCLC patients from 2004 to 2010 was used to identify cases with nodal relapses. Controls were matched to cases, 2:1, controlling for tumor volume (ie, same or greater) and tumor location (ie, same lobe). Reference (normalized to equivalent dose for 2-Gy fractions [EQD2]) point doses at the ipsilateral hilum and carina, demographic data, and clinical outcomes were extracted from the medical records. Univariate conditional logistical regression analyses were performed with variables of interest. Cases and controls were well matched except for size. The controls, as expected, had larger gross tumor volumes (P=.02). The mean ipsilateral hilar doses were 9.6 Gy and 22.4 Gy for cases and controls, respectively (P=.014). The mean carinal doses were 7.0 Gy and 9.2 Gy, respectively (P=.13). Mediastinal nodal relapses, with and without ipsilateral hilar relapse, were associated with mean ipsilateral hilar doses of 3.6 Gy and 19.8 Gy, respectively (P=.01). The conditional density plot appears to demonstrate an inverse dose-effect relationship between ipsilateral hilar normalized total dose and risk of ipsilateral hilar relapse. Incidental hilar dose greater than 20 Gy is significantly associated with fewer ipsilateral hilar relapses in inoperable early stage NSCLC patients treated with SBRT.

Erratum to: Incidental dose to coronary arteries is higher in prone than in supine whole breast irradiation

Erratum to: Incidental dose to coronary arteries is higher in prone than in supine whole breast irradiation

Low incidence of new biochemical hypogonadism after intensity modulated radiation therapy for prostate cancer

PurposeTo evaluate serum testosterone and the incidence of biochemical hypogonadism in men treated with intensity modulated radiation therapy (IMRT) for prostate cancer. Methods and materialsSerum testosterone was evaluated prospectively in 51 men at pretreatment and at 6-month time points for 2 years posttreatment with IMRT for prostate cancer. Forty-one patients (80%) were treated with definitive intent and 10 patients with postprostatectomy radiation to median total doses of 7380 cGy and 6480 cGy, respectively. No patients received hormone therapy within 12 months of any serum testosterone value. Biochemical hypogonadism was defined as a total serum testosterone level ≤300 ng/dL. Incidental testicular dose was calculated using planning software when computed tomography information was available (n = 21) and using a published method of estimation when not available (n = 24), and was available for 45 patients. ResultsA statistically significant decrease in testosterone, though small in magnitude, was seen at 6 months after completion of therapy, with no significant difference by 1 year after completion of therapy. There was no increase in biochemical hypogonadism after IMRT. Below-normal pretreatment testosterone was not associated with a transient decrease. Estimated cumulative testicular dose, including dose from daily imaging, was not associated with a change in testosterone, nor was radiation therapy prescription dose or treatment intent (postoperative vs definitive). ConclusionsThe mild transient decrease in serum testosterone following IMRT monotherapy for prostate cancer is not associated with new biochemical hypogonadism.

Incidental dose to coronary arteries is higher in prone than in supine whole breast irradiation

Sparing of normal lung is best achieved in prone whole breast irradiation (WBI). However, exposure of the heart and coronary arteries might increase due to anterior movement of the heart in prone WBI. Treatment plans of 46patients with large breasts irradiated for mammary cancer after breast-conserving surgery were retrospectively analyzed. The average treated breast volume of right-sided breasts (n = 33) was 1,804ccm and 1,500ccm for left-sided breasts (n = 13). The majority had invasive cancer (96 %) of which 61 % were pT1 and 39 % pT2 tumors. All patients received radiation therapy to the breast only. For three-dimensional (3D) treatment planning, all patients underwent a noncontrast-enhanced CT in the supine position with a wingboard and a second CT in the prone position using a prone breastboard. Nontarget volumes of the lung, heart, and coronary arteries were contoured. A total dose of 50.4Gy was prescribed to the breast only. Differences were calculated for each patient and compared using the Wilcoxon signed-rank test. Treatment of left-sided breasts resulted in similar average mean heart doses in prone versus supine WBI (4.16 vs. 4.01Gy; p = 0.70). The left anterior descending artery (LAD) had significantly higher dose exposure in left versus right WBI independent of position. Prone WBI always resulted in significantly higher exposures of the right circumflex artery (RCA) and LAD as compared to supine WBI. In left WBI, the mean LADprone was 33.5Gy vs. LADsupine of 25.6Gy (p = 0.0051). The V20prone of the LAD was 73.6 % vs. V20supine 50.4 % (p = 0.0006). The heart dose is not different between supine and prone WBI. However, in left WBI the incidental dose to the LAD with clinically relevant doses can be significantly higher in prone WBI. This is discussed controversially in the literature as it might depend on contouring and treatment techniques. We recommend contouring of LAD if patients are treated in prone WBI and evaluation of alternative treatment techniques for optimal sparing of coronary arteries.

Incidental Mediastinal Dose Does Not Explain Low Mediastinal Node Recurrence Rates in Patients With Early-Stage NSCLC Treated With Stereotactic Body Radiotherapy

BackgroundPatients with stage I non–small-cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT) do not undergo a staging mediastinoscopy, yet reported mediastinal recurrence rates appear lower than in patients undergoing surgical resection. We determined incidental SBRT doses to assess whether this could account for the low rates of recurrence. Patients and MethodsBetween March 2009 and September 2012, we reviewed cases of patients with inoperable lung tumors (n = 136) treated with SBRT at our institution. The SBRT regimen was 54 Gy in 3 fractions with positron emission tomography/computed tomography (PET/CT) staging. Incidental doses to the mediastinal lymph node stations (MLNSs), primary tumor control, locoregional (LR), distant control (DC), and overall survival (OS) rates were determined. ResultsForty-six patients with stage I NSCLC met the inclusion criteria. The calculated median incidental SBRT dose to all MLNSs was < 5 Gy for the majority of patients (75%). At a median follow-up of 16.8 months (0.6-38.9 months), the 1- and 2-year primary tumor control, LR, OS, and DC rates were 100% and 95.5%, 97.4% and 81.7%, 88.1% and 81%, and 96.9% and 86.9%, respectively. Only 2 patients (4.9%) had mediastinal recurrence, with incidental SBRT doses to MLNSs that were similar to the rest of patients (P > .05). ConclusionLow mediastinal recurrence rates in stage I NSCLC treated with SBRT validates the omission of staging mediastinoscopy. The low incidental dose to MLNSs does not seem to explain the low mediastinal recurrence in the majority of patients. Our findings also confirm that prophylactic radiation to the mediastinum is not necessary and support the hypothesis that local ablation of the primary lesion could indirectly affect subclinical nodal disease through unknown mechanisms.

Multiple comparisons permutation test for image based data mining in radiotherapy

Comparing incidental dose distributions (i.e. images) of patients with different outcomes is a straightforward way to explore dose-response hypotheses in radiotherapy. In this paper, we introduced a permutation test that compares images, such as dose distributions from radiotherapy, while tackling the multiple comparisons problem. A test statistic Tmax was proposed that summarizes the differences between the images into a single value and a permutation procedure was employed to compute the adjusted p-value. We demonstrated the method in two retrospective studies: a prostate study that relates 3D dose distributions to failure, and an esophagus study that relates 2D surface dose distributions of the esophagus to acute esophagus toxicity. As a result, we were able to identify suspicious regions that are significantly associated with failure (prostate study) or toxicity (esophagus study). Permutation testing allows direct comparison of images from different patient categories and is a useful tool for data mining in radiotherapy.

Clinical Features of Radiation-induced Carotid Atherosclerosis

Carotid arteries frequently receive significant incidental doses of radiation during the treatment of malignant diseases, including head and neck cancer, breast cancer and lymphoma. Vascular injury after treatment may result in carotid artery stenosis and increased risk of neurological sequelae, such as stroke and transient ischaemic attack. The long latent interval from treatment to the development of clinical complications makes investigation of this process difficult, particularly in regard to the design of interventional clinical studies. Nevertheless, there is compelling clinical evidence that radiation contributes to carotid atherosclerosis. This overview examines the effect of radiotherapy on the carotid arteries, the underlying pathological processes and their clinical manifestations. The use of serum biomarkers in risk-prediction models and the potential value of new imaging techniques as tools for defining earlier surrogate end points will also be discussed.

Incidental Mediastinal Dose Does Not Explain Low Mediastinal Nodal Recurrence Rates in Early-Stage NSCLC Patients Treated With SBRT

Reported mediastinal recurrence rates in SBRT for stage I NSCLC are low relative to patients who undergo surgical resection (7%-21%). We hypothesized whether incidental dose to the mediastinum could account for the low rates of recurrence in these patients.

Incidental radiation to axilla in early breast cancer treated with intensity modulated tangents and comparison with conventional and 3D conformal tangents

PurposeTo analyze incidental radiation doses to minimally dissected axilla with Intensity modulated radiotherapy (IMRT), 3D conformal radiotherapy (3DCRT) and standard tangents (ST). Methods & materialsWe prospectively evaluated incidental radiation to axilla in fifty cases of early breast cancer treated with breast conservation surgery with sentinel node biopsy alone followed by whole breast irradiation with IMRT. Three plans were devised for each CT dataset, comprising ST, 3DCRT and IMRT tangents. Doses to axillary nodal levels I, II and III were evaluated for mean dose, V95, V90, V80 and V50. Comparisons were made using ANOVA. ResultsThe mean doses delivered to axilla by the three techniques (IMRT, 3DCRT, ST) were: 78% (range 67–90, SD ± 5.2%), 80% (63–95, ±7.5%) and 87% (73–98, ±4.8%) for level I (IMRT vs ST; p = 0.037); 70% (46–89, ±12.4%), 72% (34–93, ±15.5%) and 65% (29–87, ±11.8%) for level II; and 51% (28–76, ±11.1%), 53% (19–86, ±13.7%) and 41% (6–72, ±10.6%) for level III, respectively. V90 values (volume receiving 90% of dose) for the three techniques were 49% (43–53, ±2.7%), 57% (51–65, ±3.1%) and 73% (65–80, ±3.4%) for level I (IMRT vs ST; p = 0.029); 35% (26–42, ±4.7%), 41% (33–50, ±4.2%) and 25% (17–36, ±4.5%) for level II (IMRT vs ST; p = 0.068); and 15% (9–22, ±3.4%), 16% (10–24, ±3.7%) and 8 (5–12, ±3.1%) for level III (IMRT vs ST; p = 0.039), respectively. ConclusionAxillary levels I and II (lower axilla) receive substantial amount of incidental radiation doses with all the three techniques; however, conformal techniques (IMRT, 3DCRT) deliver significantly lesser incidental radiation to lower axilla than ST technique.

SU-E-T-285: Use of Computational Human Phantoms Combined with a Treatment Planning System to Study the Sensitivity of Reconstructed Normal Tissue Dose to Patient Size and Assumptions On Second Tumor Location

Purpose: Epidemiologic studies of second cancer risk from radiotherapy require reconstruction of normal tissue doses for patients treated years ago and often rely on a single estimate, usually a mean tissue dose or less frequently, a point-dose at the site of second cancer development. However, uncertainties of dose estimates due to assumptions made in dose reconstruction, e.g., body size and location of the tumor, are rarely quantified. To assess the uncertainty of the estimated incidental breast dose from radiotherapy for Hodgkin Lymphoma, we investigated the sensitivity of the point-dose to dosimetric assumptions using computational human phantoms of different body sizes imported into a commercial treatment planning system (TPS). Methods: We converted three adult female hybrid phantoms representing the 20th, 50th, and 80th weight percentiles to DICOM images that we imported to a TPS featuring a three-dimensional convolution/superposition algorithm. We simulated opposite mantle fields with 6 MV photons and typical lung blocks (transmission, 5%) to deliver 40 Gy at the phantom mid-plane. We located a point in the left breast 1.7 cm below the surface and in-field to reconstruct point-dose for each phantom. We retrieved the lateral dose profile starting at the point and crossing the block boundary. Results: Point-doses were 43, 44, and 46 Gy for the three phantoms with 20th, 50th, and 80th weight percentiles, respectively. To deliver 40 Gy at mid-plane of the phantoms, a greater number of monitor units were required for thicker phantoms, resulting in a greater shallow dose. The lateral dose profile showed that the point-dose estimate can vary by a factor of 10 depending on whether the point is under the block or not. Conclusion: Our new dose reconstruction strategy, combining computational human phantoms and a TPS, enabled us to examine the sensitivity of point-dose estimate to patient size and assumed second tumor location.

A treatment planning comparison of four target volume contouring guidelines for locally advanced pancreatic cancer radiotherapy

Background and purposeContouring of target volumes varies significantly in radiotherapy of pancreatic ductal adenocarcinoma (PDAC). There is a lack of consensus as to whether elective lymph nodes (eLN’s) should be included or not in the planning target volume (PTV). In the present study we analyzed the dosimetric coverage of the eLN’s and organs at risk (OAR) by comparing four different contouring guidelines. Methods and materialsPTVs were delineated with (Oxford and RTOG guidelines) or without (Michigan and SCALOP guidelines) including the eLNs in eleven patients with PDAC. eLNs included the peripancreatic, paraaortic, paracaval, celiac trunk, superior mesenteric and portal vein clinical target volumes (CTVs). A 3D-CRT plan (50.40Gy in 28 fractions) was performed to analyze and compare the dosimetric coverage of all eLNs and OAR between the 4 contouring guidelines. ResultsThe size of Oxford and RTOG PTVs was comparable and significantly larger than the SCALOP and Michigan PTVs. Interestingly the eLNs received a significant amount of incidental dose irradiation by PTV-based plans that only aimed to treat the tumor without the eLNs. The dosimetric coverage of eLN presented a large variability according to the respective contouring methods. The difference in the size of the 4 PTVs was reflected to the dose distribution at the OAR. ConclusionsOur study provides important information regarding the impact of different contouring guidelines on the dose distribution to the eLNs and the OAR in patients with locally advanced PDAC treated with radiotherapy.

Radiation Dose to the Esophagus From Breast Cancer Radiation Therapy, 1943-1996: An International Population-Based Study of 414 Patients

To provide dosimetric data for an epidemiologic study on the risk of second primary esophageal cancer among breast cancer survivors, by reconstructing the radiation dose incidentally delivered to the esophagus of 414 women treated with radiation therapy for breast cancer during 1943-1996 in North America and Europe. We abstracted the radiation therapy treatment parameters from each patient's radiation therapy record. Treatment fields included direct chest wall (37% of patients), medial and lateral tangentials (45%), supraclavicular (SCV, 64%), internal mammary (IM, 44%), SCV and IM together (16%), axillary (52%), and breast/chest wall boosts (7%). The beam types used were (60)Co (45% of fields), orthovoltage (33%), megavoltage photons (11%), and electrons (10%). The population median prescribed dose to the target volume ranged from 21 Gy to 40 Gy. We reconstructed the doses over the length of the esophagus using abstracted patient data, water phantom measurements, and a computational model of the human body. Fields that treated the SCV and/or IM lymph nodes were used for 85% of the patients and delivered the highest doses within 3 regions of the esophagus: cervical (population median 38 Gy), upper thoracic (32 Gy), and middle thoracic (25 Gy). Other fields (direct chest wall, tangential, and axillary) contributed substantially lower doses (approximately 2 Gy). The cervical to middle thoracic esophagus received the highest dose because of its close proximity to the SCV and IM fields and less overlying tissue in that part of the chest. The location of the SCV field border relative to the midline was one of the most important determinants of the dose to the esophagus. Breast cancer patients in this study received relatively high incidental radiation therapy doses to the esophagus when the SCV and/or IM lymph nodes were treated, whereas direct chest wall, tangentials, and axillary fields contributed lower doses.

Patterns of locoregional relapses for patients with esophageal cancer for whom exclusive chemoradiotherapy failed: A plea for dose escalation and elective nodal irradiation.

99 Background: Nearly half of the patients (pts) with an esophageal cancer (EC) have a locoregional failure (LRF) after exclusive chemoradiation (eCRT). eCRT delivering 50Gy remains the standard of care for non operable pts. We aim to evaluate the patterns of LRF with respect to planned dose and/or the incidental (unplanned) dose that covered LRF. Methods: Twenty-two pts with EC who failed locally and/or regionally in their follow-up were exclusively reviewed. All the pts have been initially treated (t0) in a curative intent with eCRT. Co-image registration of CT or PET-CT at time of failure and planning CT at t0 was used for image fusion. Each nodal failure (Nf) and each local failure of the primary tumor (Lf) has been outlined, as well as each nodal station (NS) including Nf according to the RTOG classification. Dosimetric parameters in relation with Lf, Nf and involved NS were derived from the initial dosimetric plan. Results: All the patients underwent eCRT including a 5-FU based chemotherapy regimen. Eighteen patients were treated with elective nodal irradiation (ENI) whereas 4 pts did not. The median dose delivered was 50Gy [50Gy-64Gy]. In the follow-up period, 14 pts were in complete response, 3 pts in partial response, 4 pts had a progressive disease (1pt unknown). The median delay between the start of radiotherapy and LRF was 14.3 months [4.27-48.46]. 13 pts had a Lf (included in “planned-dose”), 9 pts had a Nf, 2 pts had a Lf with Nf and 7 pts had a concomittant distant failure. Among pts with Nf, 8 failures were in-field whereas 3 pts had an out-field relapse. Re-calculated doses for NS delineated on the CT performed at t0 were significantly less important than the planned dose (see Table). Conclusions: Our results suggest that an inadequate dose to both the primary tumor and NS could explain high LRF rates observed in EC. A French randomized phase III trial (NCT 01348217) is currently testing a higher dose to the primary tumor and/or ENI with IMRT in an attempt to improve locoregional control. [Table: see text]

Incidental nodal irradiation with involved-field conformal radiotherapy for patients with thoracic esophageal squamous cell carcinoma

Objective To quantify the incidental irradiation dose (ⅡD) to lymph node stations of esophagus when treating patients with T1-4N0 M0 thoracic esophageal squamous cell carcinoma (ESCC) with a dose of 60 Gy/30f.Methods Twenty-nine patients with medically inoperable T1-4N0M0 thoracic ESCC were treated with three-dimensional radiotherapy on involved-field.The conformal CTV was re-created using a 3 cm margin in the proximal and distal direction (following the course of the esophagus) beyond the barium esophagogram,endoscopic examination and CT defined GTV and a 0.5 cm margin in the lateral and anteroposterior directions of the CT defined GTV.The PTV encompassed 1 cm proximal and distal margins,0.5 cm radiaI margin on the basis of CTV.Cervical,mediastinal and abdominal lymph nodes were delineated respectively.Equivalent uniform dose (EUD) and other dosimetric paraneters were calculated for each nodal station.Nodal region whose metastasis rate is greater than 5％ was considered a high risk lymph node subgroups.Results Under a 60 Gy dose prescription,the median Dmean and EUD,V40 and V50 were ≥40 Gy,≥85％ and ≥75％ in most of the high risk nodal regions.For the subgroups whose EUD were less than 40 Gy,most of the ⅡD of these regions was significantly associated with the length and location of esophageal tumor (r =0.892,P =0.000).Conclusions Lymph node stations nearby of ESCC received considerable ⅡD with involved-field irradiation which could control subclinical lesions.But more clinical studies should be needed. Key words: Esophageal neoplasms/three-dimensional radiotherapy; Involved-field irradiation; Lymph node stations; Dosimetry

Three-dimensional conformal radiation for esophageal squamous cell carcinoma with involved-field irradiation may deliver considerable doses of incidental nodal irradiation

BackgroundTo quantify the incidental irradiation dose to esophageal lymph node stations when irradiating T1-4N0M0 thoracic esophageal squamous cell carcinoma (ESCC) patients with a dose of 60 Gy/30f.MethodsThirty-nine patients with medically inoperable T1–4N0M0 thoracic ESCC were treated with three-dimensional conformal radiation (3DCRT) with involved-field radiation (IFI). The conformal clinical target volume (CTV) was re-created using a 3-cm margin in the proximal and distal direction beyond the barium esophagogram, endoscopic examination and CT scan defined the gross tumor volume (GTV) and a 0.5-cm margin in the lateral and anteroposterior directions of the CT scan-defined GTV. The PTV encompassed 1-cm proximal and distal margins and 0.5-cm radial margin based on the CTV. Nodal regions were delineated using the Japanese Society for Esophageal Diseases (JSED) guidelines and an EORTC-ROG expert opinion. The equivalent uniform dose (EUD) and other dosimetric parameters were calculated for each nodal station. Nodal regions with a metastasis rate greater than 5% were considered a high-risk lymph node subgroup.ResultsUnder a 60 Gy dosage, the median Dmean and EUD was greater than 40 Gy in most high-risk nodal regions except for regions of 104, 106tb-R in upper-thoracic ESCC and 101, 104-R, 105, 106rec-L, 2, 3&7 in middle-thoracic ESCC and 107, 3&7 in lower-thoracic ESCC. In the regions with an EUD less than 40Gy, most incidental irradiation doses were significantly associated with esophageal tumor length and location.ConclusionsLymph node stations near ESCC receive considerable incidental irradiation doses with involved-field irradiation that may contribute to the elimination of subclinical lesions.

Incidental Nodal Irradiation in Stage III Lung Cancer Treated With Involved-Field Radiation: Comparison Between 3DCRT and IMRT

o However, caution must be taken when delivering IFRT with IMRT if there is high risk for subclinical disease in the AP window nodal regions. Sonam Sharma, Jonathan Whaley, Jennifer Wei Zou, Annemarie Fernandes, Eric Xanthopoulos, Charles B. Simone II, John P. Christodouleas, Stefan Both, Ramesh Rengan, Smith Apisarnthanarax Incidental nodal irradiation in stage III lung cancer treated with involved field radiation: comparison between 3DCRT and IMRT