Heather Warkentin

Experimental Validation of the Eclipse AAA Algorithm

The present study evaluates the performance of a newly released photon‐beam dose calculation algorithm that is incorporated into an established treatment planning system (TPS). We compared the analytical anisotropic algorithm (AAA) factory‐commissioned with “golden beam data” for Varian linear accelerators with measurements performed at two institutions using 6‐MV and 15‐MV beams. The TG‐53 evaluation regions and criteria were used to evaluate profiles measured in a water phantom for a wide variety of clinically relevant beam geometries. The total scatter factor (TSF) for each of these geometries was also measured and compared against the results from the AAA. At one institute, TLD measurements were performed at several points in the neck and thoracic regions of a Rando phantom; at the other institution, ion chamber measurements were performed in a CIRS inhomogeneous phantom. The phantoms were both imaged using computed tomography (CT), and the dose was calculated using the AAA at corresponding detector locations. Evaluation of measured relative dose profiles revealed that 97%, 99%, 97%, and 100% of points at one institute and 96%, 88%, 89%, and 100% of points at the other institution passed TG‐53 evaluation criteria in the outer beam, penumbra, inner beam, and buildup regions respectively. Poorer results in the inner beam regions at one institute are attributed to the mismatch of the measured profiles at shallow depths with the “golden beam data.” For validation of monitor unit (MU) calculations, the mean difference between measured and calculated TSFs was less than 0.5%; test cases involving physical wedges had, in general, differences of more than 1%. The mean difference between point measurements performed in inhomogeneous phantoms and Eclipse was 2.1% (5.3% maximum) and all differences were within TG‐53 guidelines of 7%. By intent, the methods and evaluation techniques were similar to those in a previous investigation involving another convolution–superposition photon‐beam dose calculation algorithm in another TPS, so that the current work permitted an independent comparison between the two algorithms for which results have been provided. PACS number: 87.53.Dq

Correlation between saliva production and quality of life measurements in head and neck cancer patients treated with intensity-modulated radiotherapy.

Purpose:To investigate the strength of correlation between measured saliva flow rates and various toxicity endpoints commonly used in head and neck cancer (HNC) treatment. Materials and Methods:All patients enrolled in a phase II study using intensity modulated radiotherapy (IMRT) for HNC treatment underwent whole mouth saliva flow measurements (stimulated and unstimulated). They were also assessed for salivary gland toxicity using Radiation Therapy Oncology Group (RTOG) late toxicity grading and 9 items representing patient-graded toxicities from 2 questionnaires (Xerostomia questionnaire and University of Washington quality of life). For each patient, saliva flow rates and quality of life (QOL) data were collected preradiotherapy (RT) and at 3 intervals post-RT (3, 6, and 12 months). Results:A total of 188 sets of coregistered data were obtained for 47 patients over a period of approximately 4 years. Saliva production and mean QOL dropped significantly immediately after RT, but there was a statistically significant recovery in both parameters between 3- and 12-month post-RT. By 12 months, post-RT the mean QOL scores had returned to pre-RT baseline, although mean stimulated saliva production remained 58% below baseline. Conclusion:Patients with HNC treated with IMRT experienced a small drop in QOL which recovered to baseline by 12 months post-RT. There was no statistically significant correlation seen between global health-related QOL scores and stimulated saliva production rates in the post-RT period.

A treatment planning study comparing helical tomotherapy with intensity-modulated radiotherapy for the treatment of anal cancer

PURPOSE A planning study to compare helical tomotherapy (HT) and intensity-modulated radiotherapy (IMRT) for the treatment of anal canal cancer. MATERIALS AND METHODS Sixteen (8 males and 8 females) patients with anal cancer previously treated radically were identified. HT and IMRT plans were generated and dosimetric comparisons of the plans were performed. The planning goals were to deliver 54Gy to the tumor (PTV(54Gy)) and 48Gy to the nodes at risk (PTV(Node)) in 30 fractions. RESULTS PTVs: HT plans were more homogeneous for both men and women. Male patients: HT vs. IMRT: D(max): 55.87+/-0.58 vs. 59.17+/-3.24 (p=0.036); D(min): 52.91+/-0.36 vs. 44.09+/-6.84 (p=0.012); female patients: HT vs. IMRT: D(max): 56.14+/-0.71 vs. 59.47+/-0.81 (p=0.012); D(min): 52.36+/-0.87 vs. 50.97+/-1.42 (p=0.028). OARs: In general, HT plans delivered a lower dose to the peritoneal cavity, external genitalia and the bladder and IMRT plans resulted in greater sparing of the pelvic bones (iliac crest/femur) for both men and women. Iliac crest/femur: the difference was significant only for the mean V10Gy of iliac crest in women (p< or =0.012). External genitalia: HT plans achieved better sparing in women compared to men (p< or =0.046). For men, the mean doses were 18.96+/-3.17 and 15.72+/-3.21 for the HT and IMRT plan, respectively (p< or =0.017). Skin: both techniques achieved comparable sparing of the non-target skin (p=NS). CONCLUSIONS HT and IMRT techniques achieved comparable target dose coverage and organ sparing, whereas HT plans were more homogeneous for both men and women.

Dose–volume analysis of locoregional recurrences in head and neck IMRT, as determined by deformable registration: A prospective multi-institutional trial

BACKGROUND AND PURPOSE Although IMRT for head and neck cancer is widely accepted, the implications of sparing normal tissue immediately adjacent to target volumes are not well known. MATERIALS AND METHODS Between 2002 and 2007, 124 patients with head and neck cancer were treated with surgery and postoperative IMRT (n=79) or definitive RT (n=45). Locoregional recurrences were analyzed for location relative to target volumes, and dosimetry. RESULTS With a median follow-up of 26.1months, a total of 16 locoregional recurrences were observed. The five-year actuarial locoregional disease-free survival was 82% [95% CI, 72-90%]. Analysis of 18 distinct sites of locoregional failure revealed that five of these failures were within the high dose clinical target volume (CTV), nine failures were at the margin of the CTV, and four recurrences were outside the CTV. The mean dose delivered to these recurrent volumes was 63.1 Gy [range: 57-68 Gy], while the mean dose to the coolest 1cc within each recurrence was 60.0 Gy [range: 51-67 Gy]. There were two periparotid recurrences observed. CONCLUSIONS We observed excellent locoregional control rates overall. The majority of recurrences occur within high dose regions of the neck and not near the spared parotid glands.

Prospective phase II study of tomotherapy based chemoradiation treatment for locally advanced anal cancer

BACKGROUND AND PURPOSE To evaluate toxicity, local control, and survival of anal cancer patients treated with helical tomotherapy (HT) and concurrent 5-fluorouracil and mitomycin-C (5FU/MMC). MATERIALS AND METHODS Fifty-seven patients were treated with HT and concurrent 5FU/MMC. The planning objectives were to deliver 54 Gy to the tumor (PTV54) and 45 Gy to the nodes at risk (PTV45) in 30 fractions. Patients were reviewed for toxicity weekly during HT, every 6 weeks for 3 months, and then every 3-4 months for 5 years. RESULTS The median follow-up was 40 months. The median age was 58 years (range: 37-83). Stage distribution: stage II-48%, IIIA-18%, IIIB-34%. The majority of patients developed ⩽ grade 2 acute toxicity scores. The most common ⩾ grade 3 acute toxicity was neutropenia (40%). Common late toxicities were grade 2 anal incontinence (16%) and telangiectasia (12%). The 3 year colostomy-free survival rate was 77% (95% CI: 61-87%), 3 year disease-free survival rate was 80% (CI: 66-89%), and 3 year overall survival was 91% (CI: 77-96%). CONCLUSIONS Incorporation of HT with concurrent 5FU/MMC had low treatment-related acute and late morbidity with few treatment breaks. However, the expected dosimetric benefit for hematological toxicity was not experienced clinically.

Skin-sparing Helical Tomotherapy vs 3D-conformal Radiotherapy for Adjuvant Breast Radiotherapy: In Vivo Skin Dosimetry Study

PURPOSE We investigated whether treatment-planning system (TPS)-calculated dose accurately reflects skin dose received for patients receiving adjuvant breast radiotherapy (RT) with standard three-dimensional conformal RT (3D-CRT) or skin-sparing helical tomotherapy (HT). METHODS AND MATERIALS Fifty patients enrolled in a randomized controlled trial investigating acute skin toxicity from adjuvant breast RT with 3D-CRT compared to skin-sparing HT, where a 5-mm strip of ipsilateral breast skin was spared. Thermoluminescent dosimetry or optically stimulated luminescence measurements were made in multiple locations and were compared to TPS-calculated doses. Skin dosimetric parameters and acute skin toxicity were recorded in these patients. RESULTS With HT there was a significant correlation between calculated and measured dose in the medial and lateral ipsilateral breast (r = 0.67, P<.001; r = 0.44, P=.03, respectively) and the medial and central contralateral breast (r = 0.73, P<.001; r = 0.88, P<.001, respectively). With 3D-CRT there was a significant correlation in the medial and lateral ipsilateral breast (r = 0.45, P=.03; r = 0.68, P<.001, respectively); the medial and central contralateral breast (r = 0.62, P=.001; r = 0.86, P<.001, respectively); and the mid neck (r = 0.42, P=.04, respectively). On average, HT-calculated dose overestimated the measured dose by 14%; 3D-CRT underestimated the dose by 0.4%. There was a borderline association between highest measured skin dose and moist desquamation (P=.05). Skin-sparing HT had greater skin homogeneity (homogeneity index of 1.39 vs 1.65, respectively; P=.005) than 3D-CRT plans. HT plans had a lower skin(V50) (1.4% vs 5.9%, respectively; P=.001) but higher skin(V40) and skin(V30) (71.7% vs 64.0%, P=.02; and 99.0% vs 93.8%, P=.001, respectively) than 3D-CRT plans. CONCLUSION The 3D-CRT TPS more accurately reflected skin dose than the HT TPS, which tended to overestimate dose received by 14% in patients receiving adjuvant breast RT.

Patient reported quality of life after helical IMRT based concurrent chemoradiation of locally advanced anal cancer

BACKGROUND AND PURPOSE Concurrent chemoradiation (CCRT) is the standard treatment for locally advanced anal canal carcinoma, although treatment-related side effects can affect patient quality of life (QOL). The purpose was to prospectively evaluate the effects of Tomotherapy (HT) based CCRT on patient reported QOL in locally advanced anal cancer. PATIENTS AND METHODS Fifty-four patients treated with HT and concurrent 5-fluorouracil/mitomycin-C underwent QOL evaluation at baseline, after treatment, and during follow-up with EORTC core (QLQ-C30) and colorectal (QLQ-CR29) questionnaires. The QOL scores at baseline and post-treatment were compared. RESULTS All C30 functional symptoms, except emotional and cognitive functioning, were impaired end-of-treatment and recovered by 3months follow-up. The majority of symptom scores were worse end-of-treatment but recovered by 3months except for fecal incontinence (FI), diarrhea, urinary incontinence (UI), and dyspareunia which persisted. FI returned to baseline at 12months while diarrhea, UI, and dyspareunia persisted. CONCLUSIONS Most impaired functions and symptoms following HT based CCRT were temporary and improved by 3months post-therapy. Late complications affecting QOL were FI, sexual function, UI, and diarrhea. Our observations support routine use of IMRT and emphasize the significance of precise evaluation of sexual, urinary, and anorectal functions before starting CCRT and routine incorporation of QOL evaluations.

Intensity-Modulated Radiotherapy (IMRT) vs Helical Tomotherapy (HT) in Concurrent Chemoradiotherapy (CRT) for Patients with Anal Canal Carcinoma (ACC): an analysis of dose distribution and toxicities

PurposeIntensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT) have been adopted for radiotherapy treatment of anal canal carcinoma (ACC) due to better conformality, dose homogeneity and normal-tissue sparing compared to 3D-CRT. To date, only one published study compares dosimetric parameters of IMRT vs HT in ACC, but there are no published data comparing toxicities. Our objectives were to compare dosimetry and toxicities between these modalities.Methods and materialsThis is a retrospective study of 35 ACC patients treated with radical chemoradiotherapy at two tertiary cancer institutions from 2008–2010. The use of IMRT vs HT was primarily based on center availability. The majority of patients received fluorouracil (5-FU) and 1–2 cycles of mitomycin C (MMC); 2 received 5-FU and cisplatin. Primary tumor and elective nodes were prescribed to ≥54Gy and ≥45Gy, respectively. Patients were grouped into two cohorts: IMRT vs HT. The primary endpoint was a dosimetric comparison between the cohorts; the secondary endpoint was comparison of toxicities.Results18 patients were treated with IMRT and 17 with HT. Most IMRT patients received 5-FU and 1 MMC cycle, while most HT patients received 2 MMC cycles (p < 0.01), based on center policy. HT achieved more homogenous coverage of the primary tumor (HT homogeneity and uniformity index 0.14 and 1.02 vs 0.29 and 1.06 for IMRT, p = 0.01 and p < 0.01). Elective nodal coverage did not differ. IMRT achieved better bladder, femoral head and peritoneal space sparing (V30 and V40, p ≤ 0.01), and lower mean skin dose (p < 0.01). HT delivered lower bone marrow (V10, p < 0.01) and external genitalia dose (V20 and V30, p < 0.01). Grade 2+ hematological and non-hematological toxicities were similar. Febrile neutropenia and unscheduled treatment breaks did not differ (both p = 0.13), nor did 3-year overall and disease-free survival (p = 0.13, p = 0.68).ConclusionsChemoradiotherapy treatment of ACC using IMRT vs HT results in differences in dose homogenity and normal-tissue sparing, but no significant differences in toxicities.

Po‐Thur Eve General‐06: Experimental Validation of the Eclipse AAA Algorithm

The Medical Physics departments of the Tom Baker Cancer Center (TBCC) and the Cross Cancer Institute (CCI) independently performed preliminary evaluation of the new Analytical Anisotropic Algorithm (AAA) implemented in Varians Eclispe (v. 6.0) treatment planning system (TPS). The TPS was pre‐commissioned with “Golden Beam Data” from the vendor. We measured central and off‐axis profiles in several beam configurations including: open square, rectangular and asymmetric (half‐blocked) beams; wedged square and half‐blocked beams; square fields at three SSDs; open and wedged oblique beams; irregular field defined by MLC and cerrobend blocks. All measurements were performed on Varian 2100EX linear accelerators. Measurements were made to assess the dose in heterogeneous media at both the CCI (CIRS Thorax IMRT phantom) and at the TBCC (TLDs in a Rando phantom). Profiles were evaluated in the buildup, penumbra, inner and outer beam regions as per AAPM Task Group 53. Measured and calculated profiles agreement was very good in all regions except for the inner beam region at the CCI, attributed a difference in interpolation schemes at the two institutions and the large volume ion chamber used for measurements. The AAA penumbra was also found to be steeper than measured penumbra since AAA was pre‐commissioned using diode measurements. Total scatter factors for most measurements differed by less than 2% from the calculated ones except for the hard wedges where differences up to 4% were found. Anthropomorphic phantoms measurements differed from AAA by as much as 5.6%. Funding provided by Varian.

Peri-anal surface dose in anal canal VMAT radiotherapy

Skin bolus may routinely be used in the perineum to build up the surface dose in the treatment of anal cancer (ACC); this may contribute to significant acute skin toxicity. Skin bolus may not be needed with the introduction of modern radiotherapy techniques if these planning techniques would achieve adequate surface dose. Our study is to ascertain if appropriate skin dose can be achieved without the use of bolus when VMAT is used in the treatment of ACC.