Evaluation of Heart Dose for Left-Sided Breast Cancer Patients Over an 11-Year Period Spanning the Transition From 2-Dimensional to 3-Dimensional Planning.

INTRODUCTION/BACKGROUND: We evaluated heart dose from left breast radiotherapy with 2-dimensional (2D) versus 3-dimensional (3D) plans. PATIENTS AND METHODS: Treatment plans from patients treated with standard fractionation for left breast cancer from 2003 to 2013 were reviewed, with patients grouped into 3 cohorts: 2003 to 2004 ("2D", with computed tomography scans for dose calculation but fields defined using simulation films; n = 29), 2005 to 2006 ("2D-post," after several influential articles on heart dose were published; n = 31), and 2007 to 2013 ("3D"; n = 256). All patients were treated with free-breathing technique. Heart volumes were retrospectively contoured for the earlier 2 cohorts. Mean heart dose (MHD) and percentage of structure receiving at least 25 Gy (V25 Gy) and percentage of structure receiving at least 5 Gy for the whole heart, left ventricle (LV), right ventricle (RV), and both ventricles were recorded and compared among cohorts. RESULTS: MHD was 345 cGy (2D), 213 cGy (2D-post) and 213 cGy (3D). LV V25 Gy was 6.3%, 1.5%, and 1.1%, respectively. Lower doses were seen over time for all indices (analysis of variance, P < .0001). Post hoc tests indicated significantly higher doses for 2D versus 2D-post or 3D cohorts (P ≤ .001) for all parameters except RV V25 Gy (P = .24). CONCLUSION: Heart doses were higher with 2D versus 3D plans. Cardiac doses and resulting toxicity with modern 3D planning might be lower than those in previous reports.

Dose-Response Relationships for Meningioma Radiosurgery.

OBJECTIVE: Dose-response relationships for meningioma radiosurgery are poorly characterized. We evaluated determinants of local recurrence for meningiomas treated with Gamma Knife radiosurgery (GKRS), to guide future treatment approaches to optimize tumor control. MATERIALS AND METHODS: A total of 101 consecutive patients (108 tumors) who underwent GKRS for benign, atypical, or malignant meningiomas between 1998 and 2011 were studied. Local recurrence was assessed. Cox proportional hazards and logistic regression analyses were used to determine the association of patient-related, tumor-related, and treatment-related characteristics with local recurrence. Acute and late toxicity was evaluated. RESULTS: World Health Organization (2007 classification) tumor grade was I (82%), II (11%), or III (7%). Median dose was 14 Gy (range, 10 to 18 Gy) for grade I tumors and 16 Gy (range, 12 to 20 Gy) for grade II and III tumors. Median follow-up was 25 months (maximum, 17 y). Two- /5-year actuarial local control rates were 100%/98% for grade I tumors and 76%/56% for grade II/III tumors. Higher tumor grade and lower GKRS dose were associated with local failure. In this cohort, there was a 42% relative reduction in local recurrence for each 1 Gy of dose escalation. CONCLUSIONS: Treatment was well tolerated with no moderate or severe toxicity. Tumor control was excellent in benign tumors and suboptimal in higher grade tumors. Because the main determinant of local recurrence was GKRS dose, we recommend dose escalation for atypical or malignant tumors to doses between 16 and 20 Gy where critical structures allow.

Inverse Planned High-Dose-Rate Brachytherapy for Locoregionally Advanced Cervical Cancer: 4-Year Outcomes.

PURPOSE: Evaluate the efficacy and toxicity of image guided brachytherapy using inverse planning simulated annealing (IPSA) high-dose-rate brachytherapy (HDRB) boost for locoregionally advanced cervical cancer. METHODS AND MATERIALS: From December 2003 through September 2009, 111 patients with primary cervical cancer were treated definitively with IPSA-planned HDRB boost (28 Gy in 4 fractions) after external radiation at our institution. We performed a retrospective review of our experience using image guided brachytherapy. Of the patients, 70% had a tumor size >4 cm, 38% had regional nodal disease, and 15% had clinically evident distant metastasis, including nonregional nodal disease, at the time of diagnosis. Surgical staging involving pelvic lymph node dissection was performed in 15% of patients, and 93% received concurrent cisplatin-based chemotherapy. Toxicities are reported according to the Common Terminology Criteria for Adverse Events version 4.0 guidelines. RESULTS: With a median follow-up time of 42 months (range, 3-84 months), no acute or late toxicities of grade 4 or higher were observed, and grade 3 toxicities (both acute and late) developed in 8 patients (1 constitutional, 1 hematologic, 2 genitourinary, 4 gastrointestinal). The 4-year Kaplan-Meier estimate of late grade 3 toxicity was 8%. Local recurrence developed in 5 patients (4 to 9 months after HDRB), regional recurrence in 3 (6, 16, and 72 months after HDRB), and locoregional recurrence in 1 (4 months after HDR boost). The 4-year estimates of local, locoregional, and distant control of disease were 94.0%, 91.9%, and 69.1%, respectively. The overall and disease-free survival rates at 4 years were 64.3% (95% confidence interval [CI] of 54%-73%) and 61.0% (95% CI, 51%-70%), respectively. CONCLUSIONS: Definitive radiation by use of inverse planned HDRB boost for locoregionally advanced cervical cancer is well tolerated and achieves excellent local control of disease. However, overall survival continues to be limited by the high rates of distant metastasis.

Is there a role for an external beam boost in cervical cancer radiotherapy?

OBJECTIVES: Some patients are medically unfit for or averse to undergoing a brachytherapy boost as part of cervical cancer radiotherapy. In order to be able to definitively treat these patients, we assessed whether we could achieve a boost plan that would mimic our brachytherapy plans using external beam radiotherapy. METHODS: High dose rate brachytherapy plans of 20 patients with stage IIB cervical cancer treated with definitive chemoradiotherapy were included in this study. Patients had undergone computer tomography (CT) simulations with tandem and ovoids in place. Point "A" dose was 600-700 cGy. We attempted to replicate the boost dose distribution from brachytherapy plans using intensity-modulated radiotherapy (Varian Medical Systems, Palo Alto, CA, USA), volumetric modulated arc therapy (Rapid Arc, Varian Medical Systems, Palo Alto, CA, USA), or TomoTherapy (Accuray, Inc., Sunnyvale, CA, USA) with the brachytherapy 100% isodose line as our target. Target coverage, normal tissue dose, and brachytherapy point doses were compared with ANOVA. Two-sided p-values ≤0.05 were considered significant. RESULTS: External beam plans had excellent planning target volume (PTV) coverage, with no difference in mean PTV V95% among planning techniques (range 98-100%). External beam plans had lower bladder Dmax, small intestine Dmax, and vaginal mucosal point dose than brachytherapy plans, with no difference in bladder point dose, mean bladder dose, mean small intestine dose, or rectal dose. Femoral head dose, parametria point dose, and pelvic sidewall point dose were higher with external beam techniques than brachytherapy. CONCLUSIONS: External beam plans had comparable target coverage and potential for improved sparing of most normal tissues compared to tandem and ovoid brachytherapy.

Comparison of three-dimensional versus intensity-modulated radiotherapy techniques to treat breast and axillary level III and supraclavicular nodes in a prone versus supine position.

BACKGROUND AND PURPOSE: To determine the optimal method of targeting breast and regional nodes in selected breast cancer patients after axillary dissection, we compared the results of IMRT versus no IMRT, and CT-informed versus clinically-placed fields, in supine and prone positions. MATERIALS AND METHODS: Twelve consecutive breast cancer patients simulated both prone and supine provided the images for this study. Four techniques were used to target breast, level III axilla, and supraclavicular fossa in either position: a traditional three-field three-dimensional conformal radiotherapy (3DCRT) plan, a four-field 3DCRT plan using a posterior axillary boost field, and two techniques using a CT-informed target volume consisting of an optimized 3DCRT plan (CT-planned 3D) and an intensity-modulated radiotherapy (IMRT) plan. The prescribed dose was 50 Gy in 25 fractions. RESULTS: CT-planned 3D and IMRT techniques improved nodal PTV coverage. Supine, mean nodal PTV V50 was 50% (3-field), 59% (4-field), 92% (CT-planned 3D), and 94% (IMRT). Prone, V50 was 29% (3-field), 42% (4-field), 97% (CT-planned 3D), and 95% (IMRT). Prone positioning, compared to supine, and IMRT technique, compared to 3D, lowered ipsilateral lung V20. CONCLUSIONS: Traditional 3DCRT plans provide inadequate nodal coverage. Prone IMRT technique resulted in optimal target coverage and reduced ipsilateral lung V20.

Comparison of daily cone-beam computed tomography and kilovoltage planar imaging for target localization in prostate cancer patients following radical prostatectomy.

PURPOSE: To review our initial clinical experience with image-guided radiation therapy (IGRT) using cone-beam computed tomography (CBCT) for prostate bed localization in post-radical prostatectomy (RP) patients and to compare shift and acute toxicity results to our previously published IGRT experience with daily kV planar imaging. METHODS AND MATERIALS: Fifty patients treated with intensity modulated radiation therapy (IMRT) who had image guidance using either CBCT (n = 23) or kV planar imaging (n = 27) following RP were analyzed. Shifts were recorded in anterior-posterior, superior-inferior, and left-right axes. Total error was defined as the shift from initial setup based on skin markings to isocenter. Prostate bed motion (PBM) was defined as the change in prostate bed position relative to bones. Acute toxicity was graded according to the Radiation Therapy Oncology Group morbidity criteria. RESULTS: Total error (TE) was measured in 752 CBCTs and 725 kV planar image pairs. PBM was measured in 585 CBCTs and 384 kV planar image pairs. The average magnitudes of TE and PBM in the anterior-posterior, superior-inferior, and left-right axes were greater with kV planar imaging compared to CBCT. Frequencies of acute grade 2 gastrointestinal (13% vs 7%, P = .7) and genitourinary (9% vs 11%, P = 1.0) were similar for CBCT and kV planar imaging patients. No toxicities greater than grade 2 were seen. CONCLUSIONS: These results suggest that although the magnitudes of TE and PBM were larger with kV planar compared to CBCT, the levels of acute toxicity were acceptable and comparable between the two. The reasons for the differences are unclear, but we postulate that discernment of the prostate bed on the CBCT is more difficult. Further investigation is necessary to determine the reason for the shift differences and to evaluate the benefits and risks of CBCT in this setting.

Head and neck radiotherapy compliance in an underserved patient population.

OBJECTIVES/HYPOTHESIS: Compliance to intensive multiweek radiation therapy (RT) regimens in head and neck cancer (HNC) patients is challenging, particularly among medically underserved patients with fewer financial and social resources. Treatment prolongation reduces local control and overall survival rates, making adherence to treatment a key factor in optimal outcome. We evaluated factors affecting compliance in medically underserved patients who received RT for HNC in a large municipal hospital setting in New York City. STUDY DESIGN: Retrospective review. METHODS: Treatment records of patients treated between July 2004 and August 2008 were reviewed. Number of and reasons for missed treatments were identified. Several demographic, toxicity, and treatment variables were analyzed for impact on compliance. RESULTS: Eighty consecutive HNC patients who underwent RT with a 5- to 7-week regimen were identified. Thirty-two patients (40%) missed no treatments, 36 (45%) missed one to six treatments, six (8%) missed seven to 14 treatments, two (3%) missed more than 14 treatments, and four (5%) did not complete treatment. Reasons for missed treatments were hospitalization (31% of events) and toxicity (20%). Patients with percutaneous endoscopic gastrostomy tube were more likely to miss treatments (P = .01, chi(2) test). No other variable showed a significant association with missed treatments (chi(2) test). CONCLUSIONS: Intensive RT for HNC can be delivered with very good adherence within a medically underserved population. Eighty-five percent of patients completed treatment with 0 to 6 days of interruption. Efforts to further improve adherence in this population are ongoing.

Mosquito abundance is correlated with cliff swallow (Petrochelidon pyrrhonota) colony size.

We measured the abundance of mosquitoes [primarily Aedes vexans (Meigen) and Culex tarsalis Coquillett] at cliff swallow (Petrochelidon pyrrhonota Vieillot) colonies of different sizes in southwestern Nebraska in 1999. Using CO2 traps placed inside and outside of colonies, we found that total mosquito abundance increased significantly with the number of active cliff swallow nests at a colony site. We found no effect of date or weather conditions on the number of mosquitoes caught it the different sites. By classifying the landscape from aerial photographs within a 2-km-diameter circle centered on each colony site, we found no significant relationships between habitat type near a colony site and cliff swallow colony size or mosquito abundance. Proximity to livestock could not account for our results. Culex tarsalis was proportionately more likely to be caught inside a colony than at traps 30 in away, but the proportion of C. tarsalis inside a colony did not vary with colony size. Our results cannot be explained by date- or weather-related sampling artifacts or by differences in habitat between sites. Most likely, mosquitoes, especially A. vexans, are attracted to the vicinity of large cliff swallow colonies.