Heather E. Newlin

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.

Neurotropic melanoma of the head and neck with clinical perineural invasion.

Objective:The purpose of this article is to report our experience with neurotropic melanoma, a rare malignancy that sometimes produces neurologic symptoms because of a direct extension of the primary tumor. Methods:We report 3 consecutive patients with neurotropic melanoma of the head and neck who presented with clinical perineural invasion. Results:Two patients had incompletely resectable tumors and were treated with definitive radiotherapy (RT), and 1 patient received surgery and postoperative RT. One patient experienced recurrence in a regional lymph node 30 months after RT and underwent salvage surgery; he is disease-free at 45 months after initial treatment. The remaining 2 patients are disease-free 34 months and 14 months after treatment. Conclusions:Radiotherapy alone or combined with surgery may provide relatively long-term local control in patients who have neurotropic melanoma with clinical perineural invasion.

Evaluation of kV cone-beam ct performance for prostate IGRT: a comparison of automatic grey-value alignment to implanted fiducial-marker alignment.

Purpose: Cone-beam computed tomography (CBCT) is a new image-guided radiation therapy (IGRT) technique for patient alignment in radiotherapy. The CBCT x-ray volume imaging system from Elekta allows for a variety of alignment methods. The aim of this study is to assess the accuracy of soft-tissue-based automatic alignment as compared with manual alignment using intraprostatic fiducials. Methods and Materials: All patients were treated on an Elekta Synergy S linear accelerator with kilovoltage CBCT. All alignments were performed using the x-ray volume imaging system and associated software. Automatic alignment with gray-value-based registration and manual alignment to fiducial markers were performed. Transitional corrections along each axis as well as 3-dimensional vectors were compared with evaluate the accuracy of gray-value-based registration compared with fiducials. Results: The distribution of the 3-dimensional vectors between gray-value and fiducial registrations demonstrated notable differences. The mean summed vector was 0.75 cm, with a standard deviation (SD) of 0.52 cm and range from 0.04 to 2.06 cm. There was minimal difference along the lateral direction, with a mean ± SD of −0.02 cm ± 0.13 cm. However, there were large discrepancies along the superior-inferior and anterior-posterior direction alignments, with mean ± SD values of −0.55 ± 0.48 cm and −0.31 ± 0.43 cm, respectively. Conclusions: CBCT with soft-tissue-based automatic corrections is not an accurate alignment compared with manual alignment to fiducial markers for prostate IGRT. We have concluded that a daily manual alignment to fiducials is one of the most reliable methods to maintain accuracy in prostate IGRT.

Squamous cell carcinoma of the anal margin: the university of Florida experience.

Objective:To update our experience in treating squamous cell carcinoma of the anal margin with definitive radiotherapy (RT). Methods:A total of 26 patients treated curatively with RT between 1979 and 2008, with or without concurrent chemotherapy, were retrospectively reviewed. American Joint Committee on Cancer stage distribution was: T1, N = 1; T2, N = 16; T3, N = 9; N0, N = 25; and N1, N = 1. Concurrent chemotherapy was administered in 12 of 26 patients (T2, 19%; T3, 100%). Median age was 48.5 years (range, 31–84 years) with a median follow-up of 8.4 years (range, 0.9–16.1 years). Median total dose was 59.4 Gy in 33 fractions. Elective inguinal lymph-node irradiation was administered to 23 of 25 N0 patients. Results:The 10-year cause-specific survival, disease-free survival, and overall survival were 92%, 88%, and 56%, respectively. Of the 26 patients, 24 experienced complete tumor regression; their local-control rate was 96%. Four patients developed recurrences (1 local, 2 regional, and 1 local/regional/distant). The 2 patients who did not receive elective inguinal lymph-node irradiation recurred in this region. Ten patients died of intercurrent disease between 2.0 and 15.9 years after RT. Two patients died with disease at 10.7 and 18.2 months after RT, whereas 1 patient is alive with local disease at 11.2 years after RT. The remaining 13 patients are alive and disease-free between 1.0 and 16.1 years after RT. The anal-sphincter-preservation rate was 88% with no severe long-term complications after RT. Conclusions:Patients with squamous cell carcinoma of the anal margin have a high probability of cure with sphincter preservation after RT with or without concurrent chemotherapy.

The Effect of Intravenous Contrast on Photon Radiation Therapy Dose Calculations for Lung Cancer

Objective:The aim of this study was to evaluate the effect of intravenous contrast-enhanced computed tomography (CT) scans on the photon radiation dose calculations for lung cancer treatment planning. Materials and Methods:Nonionic iodinated intravenous contrast (Iohexol) was administered during the treatment planning CT scan of 9 patients with node-positive non–small-cell lung cancer (NSCLC). The potential effect of intravenous contrast was studied by changing the density of the contrast-enhanced vessels. A total of 9 patients were treated in this study: 5 patients with intensity-modulated radiation therapy (IMRT), and 4 patients with three-dimensional (3D) conformal radiation therapy. A treatment plan was generated from an unmanipulated “normal contrast” planning scan. The same planning parameters were then applied to a “no contrast” planning scan. The effect of intravenous contrast was quantified by calculating the percent change of dose in a variety of target and normal structures. To evaluate a worst-case scenario, the comparison between “normal contrast” and “no contrast” planning scans was repeated, assigning each vessel the artificial high density of 1.3 g/cm3. Results:Dose differences between the planning image set using intravenous contrast and the image set without contrast were less than 2.5% for planning target volumes. A worst-case scenario in which normal contrast was overridden with an artificially high density of 1.3 g/cm3 led to small dose differences of less than 3%. Conclusions:Planning lung radiation therapy treatment using CT scans that contain intravenous contrast does not result in clinically significant errors in dose delivery.

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.

Unresectable Squamous Cell Carcinoma of the Lung: An Outcomes Study

PURPOSE To report survival and control rates in patients with inoperable squamous cell carcinoma (SCC). METHODS AND MATERIALS Two hundred seventy-five patients with inoperable squamous cell carcinoma of the lung (Stages I-IIIB) who received radiotherapy alone or combined with chemotherapy given with curative intent at the University of Florida between 1963 and 2006 were retrospectively analyzed. RESULTS Overall survival (OS) at 5 years for Stages I, II, and III was 10%, 14%, and 7% (p = 0.0034); local-regional control at 5 years was 51%, 38%, and 29% (p = 0.0003); and freedom from metastases at 5 years was 81%, 60%, and 65% (p = 0.0689), respectively. Patients who received doses > or = 65 Gy had improved cause-specific survival (CSS), OS, and metastasis-free survival at 5 years compared with those who received doses < 65 Gy. Five-year regional control was significantly improved with twice-daily vs. once-daily treatment (37% vs. 14%, p = 0.02). Chemotherapy significantly improved 5-year regional control (36% for patients who received chemotherapy vs. 13% for those who did not; p = 0.01). CONCLUSIONS Dose escalation, accelerated fractionation, and combined modality therapies improve outcomes in SCC of the lung. Our review of the literature highlights the different natural history for SCC vs. other non-small cell lung cancers and emphasizes the importance of tailoring treatment strategies to individual patients. At the University of Florida, we have begun treating unresectable Stage III patients with SCC of the lung using 69.6 Gy twice daily with concurrent chemotherapy.

Lung tumor motion change during stereotactic body radiotherapy (SBRT): an evaluation using MRI

The purpose of this study is to investigate changes in lung tumor internal target volume during stereotactic body radiotherapy treatment (SBRT) using magnetic resonance imaging (MRI). Ten lung cancer patients (13 tumors) undergoing SBRT (48 Gy over four consecutive days) were evaluated. Each patient underwent three lung MRI evaluations: before SBRT (MRI‐1), after fraction 3 of SBRT (MRI‐3), and three months after completion of SBRT (MRI‐3m). Each MRI consisted of T1‐weighted images in axial plane through the entire lung. A cone‐beam CT (CBCT) was taken before each fraction. On MRI and CBCT taken before fractions 1 and 3, gross tumor volume (GTV) was contoured and differences between the two volumes were compared. Median tumor size on CBCT before fractions 1 (CBCT‐1) and 3 (CBCT‐3) was 8.68 and 11.10 cm3, respectively. In 12 tumors, the GTV was larger on CBCT‐3 compared to CBCT‐1 (median enlargement, 1.56 cm3). Median tumor size on MRI‐1, MRI‐3, and MRI‐3m was 7.91, 11.60, and 3.33 cm3, respectively. In all patients, the GTV was larger on MRI‐3 compared to MRI‐1 (median enlargement, 1.54 cm3). In all patients, GTV was smaller on MRI‐3m compared to MRI‐1 (median shrinkage, 5.44 cm3). On CBCT and MRI, all patients showed enlargement of the GTV during the treatment week of SBRT, except for one patient who showed minimal shrinkage (0.86 cm3). Changes in tumor volume are unpredictable; therefore, motion and breathing must be taken into account during treatment planning, and image‐guided methods should be used, when treating with large fraction sizes. PACS number: 87.53.Ly

Does surgical closure technique affect early mammographic detection of tumor recurrence after breast-conserving therapy?

Purpose:Scarring in the tumor bed may mask or mimic local recurrence of tumor on surveillance mammography. Type of surgical closure technique used during lumpectomy may impact the pattern or density of scar tissue apparent in the tumor bed on mammography. This study sought to determine whether surgical closure type affects tumor-bed scar formation and impacts interpretation of surveillance mammography in women treated with breast-conserving therapy for early-stage breast cancer. Materials and Methods:One hundred women who received breast-conserving therapy were selected; 99 of them had 2-year post-treatment mammograms for the treated breast. Craniocaudal and mediolateral oblique views were reviewed by 3 subspecialty radiologists who routinely read mammograms. The mammograms were scored on 5-point scales for overall breast density and scarring within the tumor bed. Results:The analyses did not demonstrate greater scarring or density in breast status post superficial closure compared with breast status post full-thickness closure, or vice versa (P > 0.05 for scarring and density). There were no detectable differences between the 2 closure techniques either within the data from individual reviewers, within the composite data for the entire group of reviewers, or in instances where 2 of 3 reviewers agreed (P > 0.05). There was significant interobserver variability in scoring among the mammographers for both scarring (P = 0.001) and density (P < 0.0001). Conclusion:Based on our study of the 2-year post-treatment mammograms, there was no evidence that closure technique impacts degree of scarring in the tumor bed. However, striking interobserver variability in scoring density and scarring was noted.