Anamaria R. Yeung

Tumor Localization Using Cone-Beam CT Reduces Setup Margins in Conventionally Fractionated Radiotherapy for Lung Tumors

PURPOSE To determine whether setup margins can be reduced using cone-beam computed tomography (CBCT) to localize tumor in conventionally fractionated radiotherapy for lung tumors. METHODS AND MATERIALS A total of 22 lung cancer patients were treated with curative intent with conventionally fractionated radiotherapy using daily image guidance with CBCT. Of these, 13 lung cancer patients had sufficient CBCT scans for analysis (389 CBCT scans). The patients underwent treatment simulation in the BodyFix immobilization system using four-dimensional CT to account for respiratory motion. Daily alignment was first done according to skin tattoos, followed by CBCT. All 389 CBCT scans were retrospectively registered to the planning CT scans using automated soft-tissue and bony registration; the resulting couch shifts in three dimensions were recorded. RESULTS The daily alignment to skin tattoos with no image guidance resulted in systematic (Sigma) and random (sigma) errors of 3.2-5.6 mm and 2.0-3.5 mm, respectively. The margin required to account for the setup error introduced by aligning to skin tattoos with no image guidance was approximately 1-1.6 cm. The difference in the couch shifts obtained from the bone and soft-tissue registration resulted in systematic (Sigma) and random (sigma) errors of 1.5-4.1 mm and 1.8-5.3 mm, respectively. The margin required to account for the setup error introduced using bony anatomy as a surrogate for the target, instead of localizing the target itself, was 0.5-1.4 cm. CONCLUSION Using daily CBCT soft-tissue registration to localize the tumor in conventionally fractionated radiotherapy reduced the required setup margin by up to approximately 1.5 cm compared with both no image guidance and image guidance using bony anatomy as a surrogate for the target.

Lymph node-positive head and neck cancer treated with definitive radiotherapy: can treatment response determine the extent of neck dissection?

The purpose was to determine if postradiotherapy (RT) neck dissection can be limited to the neck levels of residual adenopathy on post‐RT computed tomography (CT).

Revisiting unnecessary larynx irradiation with whole-neck IMRT

PURPOSE To determine if whole-neck intensity-modulated radiotherapy (IMRT) spares the larynx as well as techniques that match a conventional anterior-neck field to an IMRT plan superior to the larynx. METHODS AND MATERIALS This is a dosimetric study using the treatment planning image sets from 5 consecutively treated patients with node-positive squamous cell carcinoma of the oropharynx, all with gross disease above the larynx. We compared 3 techniques for irradiating the mid- and low-neck lymphatics: whole-neck IMRT, conventional anterior-neck field with split-beam matching, and conventional anterior-neck field with gradient matching. Prescription doses for the high-, intermediate-, and standard-risk planning target volumes were 70 Gy, 60 Gy, and 50 Gy, respectively. RESULTS The mean larynx dose was similar with all techniques with median values: whole-neck IMRT, 28 Gy (range, 17-30 Gy); conventional field with split-beam matching, 26 Gy (range, 21-33 Gy); conventional field with gradient matching, 30 Gy (range, 25-31 Gy). CONCLUSIONS With meticulous attention to the details of contouring and treatment planning, it is possible to use whole-neck IMRT without increasing the risk of larynx dysfunction compared to techniques that block the larynx in a conventional anterior-neck field. We discuss the potential advantages of each technique in this article.

Optimal Image-Guidance Scenario With Cone-Beam Computed Tomography in Conventionally Fractionated Radiotherapy for Lung Tumors

Purpose:To determine the residual setup errors of several image guidance scenarios, using cone-beam computed tomography (CBCT) in conventionally fractionated radiotherapy for lung tumors. Methods:Thirteen lung cancer patients were treated with conventionally fractionated radiotherapy, using daily image guidance with CBCT, resulting in 389 CBCT scans which were registered to the planning scan using automated soft-tissue registration. Using the resulting daily alignment data, 4 imaging frequency scenarios were analyzed: (A) no imaging; (B) weekly imaging with a 3-mm threshold; (C) first 5 fractions imaged, then weekly imaging with a patient-specific threshold; and (D) imaging every other day. Results:The systematic setup error (Σ) was reduced with increasing frequency of imaging from 3.4 mm for no imaging to 1.0 mm for imaging every other day. Random setup error (σ), however, varied little regardless of the frequency of imaging: 2.9, 3.0, 3.4, and 3.2 mm for scenarios A, B, C, and D, respectively. The setup margins required to account for the residual error of each imaging scenario were 1 to 1.6 cm for scenario A, 4 to 6 mm for scenarios B and C, and 4 to 5 mm for scenario D. As the residual error of daily CBCT was not included in this analysis, these margins compare with a margin of zero for daily CBCT. Conclusions:Daily image guidance is ideal as the setup margin can be reduced by about 5 mm versus a nondaily imaging scenario. However, if daily image guidance is not possible, there is little benefit in imaging more often than once a week.

Postoperative radiotherapy for cervix cancer incidentally discovered after a simple hysterectomy for either benign conditions or noninvasive pathology.

Objective:Report the long-term outcome of patients who received postoperative radiotherapy for incidentally discovered cervix cancer following simple hysterectomy. Methods:We recorded tumor status, treatment complications, and survival of 25 patients treated at our institution from 1961 to 2004 with postoperative RT for invasive cervix cancer discovered following simple hysterectomy (median follow-up, 17 years). All patients had stage IA2-II squamous cell carcinoma (76%) or adenocarcinoma (24%) of the cervix. Results:One patient had an isolated vaginal-cuff recurrence and was cured long-term with salvage surgery. No patient died of cervix cancer. The actuarial rate of tumor control and relapse-free survival at 5, 10, and 20 years was 96%. One patient died of a treatment-related complication. Cause-specific survival was 100% at 5 and 10 years, but 92% at 20 years. Overall survival was 100% at 5 years, 95% at 10 years, and 62% at 20 years.The complications rate from therapy was surprising. The overall grade 2 to 5 complications rate was 36% (9 of 25). Twenty percent (5 of 25) of patients experienced grade 4 or 5 complications. Conclusions:This series demonstrates the price we pay for adding comprehensive radiotherapy to simple hysterectomy for early-stage cervix cancer. The findings support 2 recommendations: (1) Avoid postoperative radiotherapy by aggressively screening patients for invasive disease before performing simple hysterectomy. (2) Raise the threshold for delivering pelvic radiotherapy following simple hysterectomy with an incidental diagnosis of invasive cervix cancer. We recommend vaginal brachytherapy alone in patients with negative postoperative imaging, negative surgical margins, and <10 mm tumor invasion.

Outcomes of Definitive Radiation Therapy for Primary Vaginal Carcinoma.

Objective(s):The aim of this study was to review treatment and outcomes of patients with primary vaginal cancer treated with definitive radiotherapy. Materials and Methods:We retrospectively reviewed medical records of 71 patients with primary vaginal adenocarcinoma or squamous cell carcinoma treated with definitive radiotherapy with at least 2 years of follow-up (median follow-up, 6.24 y). Results:Ninety-three percent of patients were treated with external-beam radiotherapy plus brachytherapy (median dose, 7540 cGy); 4 patients with stage I disease and 1 patient with stage II disease were treated with brachytherapy alone (median dose, 6000 cGy). The cause-specific 5- and 10-year survival rates, respectively, were 96% and 96% for stage I patients, 75% and 68% for stage II patients, 69% and 64% for stage III patients, and 53% and 53% for stage IVA patients. The 5- and 10-year local-regional control rates for all patients were 79% and 75%, respectively. The 5- and 10-year distant metastasis-free survival rates for all patients were 87% and 85%, respectively. Sixteen patients had tumors involving the distal one third of the vagina. Of the 7 who received elective inguinal node irradiation, 0 failed in the inguinal nodes. Of the 9 who did not receive elective inguinal node irradiation, 2 failed in the inguinal nodes. Severe complications (grades 3 to 4) occurred in 16 patients (23%). Conclusions:Radiotherapy provides excellent results as definitive treatment for primary vaginal cancer, although the risk of severe complications is high. Generally, treatment should consist of both external-beam radiation therapy and brachytherapy. Inguinal nodes should be irradiated electively when the primary tumor involves the distal one third of the vagina.

Radiotherapy for juvenile nasopharyngeal angiofibroma.

PURPOSE To explain the concepts that radiation oncologists need to understand to manage patients with juvenile nasopharyngeal angiofibroma (JNA). To accomplish this goal we first describe our institutions experience with radiotherapy for JNA and then use this data set as a framework for explaining the role of radiotherapy in the treatment of this uncommon tumor. METHODS AND MATERIALS We studied the outcomes of all 24 patients treated with radiotherapy for JNA at our institution. All patients had at least 4 years of follow-up (median follow-up, 18 years). The standard dose in the first half of the series was 30 Gy in 22 treatments (1.43 Gy/treatment). After observing recurrences with this schedule, the prescription was changed to 35 to 36 Gy at 1.8 Gy/treatment. In all cases, the target volume was the primary site without an attempt to cover the regional nodes. RESULTS All recurrences were at the primary site and presented within 5 years of completing radiotherapy. There appeared to be a dose response for tumor control: 77% with 30 to 32 Gy versus 91% with 35 to 36 Gy. All recurrences following radiotherapy were successfully salvaged with surgery. The only complications from radiotherapy were cataracts in 2 patients. No patient had a significant growth abnormality or second tumor. CONCLUSIONS Surgery is the best treatment for JNA when cure is likely with low morbidity, but the threshold for using radiotherapy should be low because moderate-dose radiotherapy cures about 90% of patients with a low risk of serious complications. We recommend 36 Gy at 1.8 Gy per treatment in most cases. Elective nodal irradiation is not necessary. Radiographic response should be almost complete within a year of radiotherapy. Patients should be followed with cross-sectional imaging every 6 months for at least 5 years.

Radiotherapy following gross total resection of adult soft tissue sarcoma of the head and neck

PURPOSE This study reports the outcomes of adults with soft tissue sarcoma (STS) of the head and neck following resection and postoperative radiotherapy (RT), and provides a framework for explaining the issues that radiation oncologists must understand to manage patients with this diverse group of tumors. METHODS AND MATERIALS Twenty-four patients met the following inclusion criteria of this study: age ≥19 years, head or neck primary site, STS, with the exception of rhabdomyosarcoma, Ewing, or angiosarcoma variants, and curative-attempt treatment with gross total tumor resection followed by RT. RESULTS All patients underwent gross total tumor resection followed by adjuvant RT at our institution during the 28-year period between June 1, 1981, and December 31, 2009. This is a mature study with a median follow-up of 11 years (range, 0.6-27 years). No patient was lost to follow-up. All recurrences were at the primary site. No patient developed an isolated regional or distant recurrence. No patient developed synchronous nodal or distant recurrences at the time of local recurrence. Half of the recurrences presented within 1 year of completing RT, but there were 2 cases where we did not detect recurrence until years 6 and 8 after RT. No recurrence was successfully salvaged. The actuarial rate of local control and relapse-free survival was 83% (95% CI [confidence interval], 63%-94%) at 5 years and 73% (95% CI, 51%-87%) at 10 years. The incidence of moderate to severe treatment complications was 4%. CONCLUSIONS Our series documents that gross total resection followed by RT cures most patients (75%) with the most common types of STS of the head and neck. All recurrences were local, meaning near the primary site in tissue that received the full RT prescription dose. For this reason, modifying the approach to treatment of the primary tumor site is the only strategy that will meaningfully improve outcomes for this group of patients.

Dose–Volume Differences for Computed Tomography and Magnetic Resonance Imaging Segmentation and Planning for Proton Prostate Cancer Therapy

PURPOSE To determine the influence of magnetic-resonance-imaging (MRI)-vs. computed-tomography (CT)-based prostate and normal structure delineation on the dose to the target and organs at risk during proton therapy. METHODS AND MATERIALS Fourteen patients were simulated in the supine position using both CT and T2 MRI. The prostate, rectum, and bladder were delineated on both imaging modalities. The planning target volume (PTV) was generated from the delineated prostates with a 5-mm axial and 8-mm superior and inferior margin. Two plans were generated and analyzed for each patient: an MRI plan based on the MRI-delineated PTV, and a CT plan based on the CT-delineated PTV. Doses of 78 Gy equivalents (GE) were prescribed to the PTV. RESULTS Doses to normal structures were lower when MRI was used to delineate the rectum and bladder compared with CT: bladder V50 was 15.3% lower (p = 0.04), and rectum V50 was 23.9% lower (p = 0.003). Poor agreement on the definition of the prostate apex was seen between CT and MRI (p = 0.007). The CT-defined prostate apex was within 2 mm of the apex on MRI only 35.7% of the time. Coverage of the MRI-delineated PTV was significantly decreased with the CT-based plan: the minimum dose to the PTV was reduced by 43% (p < 0.001), and the PTV V99% was reduced by 11% (p < 0.001). CONCLUSIONS Using MRI to delineate the prostate results in more accurate target definition and a smaller target volume compared with CT, allowing for improved target coverage and decreased doses to critical normal structures.

Stereotactic Ablative Body Radiotherapy for Primary Non-Small-Cell Lung Cancer: Achieving Local Control with a Lower Biologically Effective Dose

Abstract We conducted a retrospective study of stereotactic ablative radiotherapy (SABR) for 94 patients with non-small-cell lung cancer at our institution. The patients were treated with either 50 Gy in five treatments or 48 Gy in four treatments, corresponding to biologically effective doses (BED) of 100 Gy or 105.6 Gy, respectively. The results demonstrate that, with relatively low BEDs, we can achieve excellent local control with minimal toxicity.