Predicting Pneumonitis Risk: A Dosimetric Alternative to Mean Lung Dose

PurposeTo evaluate the potential of cone-beam-CT (CB-CT) guided adaptive radiotherapy (ART) for locally advanced non-small cell lung cancer (NSCLC) for sparing of surrounding organs-at-risk (OAR).Materials and MethodsIn 10 patients with locally advanced NSCLC, daily CB-CT imaging was acquired during radio- (n = 4) or radiochemotherapy (n = 6) for simulation of ART. Patients were treated with conventionally fractionated intensity-modulated radiotherapy (IMRT) with total doses of 60–66 Gy (pPlan) (311 fraction CB-CTs). OAR were segmented on every daily CB-CT and the tumor volumes were modified weekly depending on tumor changes. Doses actually delivered were recalculated on daily images (dPlan), and voxel-wise dose accumulation was performed using a deformable registration algorithm. For simulation of ART, treatment plans were adapted using the new contours and re-optimized weekly (aPlan).ResultsCB-CT showed continuous tumor regression of 1.1 ± 0.4% per day, leading to a residual gross tumor volume (GTV) of 65.3 ± 13.4% after 6 weeks of radiotherapy (p = 0.005). Corresponding PTVs decreased to 83.7 ± 7.8% (p = 0.005). In the actually delivered plans (dPlan), both conformity (p = 0.005) and homogeneity (p = 0.059) indices were impaired compared to the initial plans (pPlan). This resulted in higher actual lung doses than planned: V20Gy was 34.6 ± 6.8% instead of 32.8 ± 4.9% (p = 0.066), mean lung dose was 19.0 ± 3.1 Gy instead of 17.9 ± 2.5 Gy (p = 0.013). The generalized equivalent uniform dose (gEUD) of the lung was 18.9 ± 3.1 Gy instead of 17.8 ± 2.5 Gy (p = 0.013), leading to an increased lung normal tissue complication probability (NTCP) of 15.2 ± 13.9% instead of 9.6 ± 7.3% (p = 0.017). Weekly plan adaptation enabled decreased lung V20Gy of 31.6 ± 6.2% (−3.0%, p = 0.007), decreased mean lung dose of 17.7 ± 2.9 Gy (−1.3 Gy, p = 0.005), and decreased lung gEUD of 17.6 ± 2.9 Gy (−1.3 Gy, p = 0.005). Thus, resulting lung NTCP was reduced to 10.0 ± 9.5% (−5.2%, p = 0.005). Target volume coverage represented by conformity and homogeneity indices could be improved by weekly plan adaptation (CI: p = 0.007, HI: p = 0.114) and reached levels of the initial plan (CI: p = 0.721, HI: p = 0.333).ConclusionIGRT with CB-CT detects continuous GTV and PTV changes. CB-CT-guided ART for locally advanced NSCLC is feasible and enables superior sparing of healthy lung at high levels of plan conformity.

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The impact of breast size on mean lung dose for patients receiving tangential radiotherapy to the whole breast

Journal of Radiotherapy in Practice ◽

10.1017/s1460396916000091 ◽

2016 ◽

Vol 15 (2) ◽

pp. 181-188

Author(s):

Ashley Schembri ◽

Susan Mercieca ◽

Nick Courtier ◽

Francis Zarb

Keyword(s):

Significant Variation ◽

Target Volume ◽

Breast Size ◽

Lung Dose ◽

Breast Radiotherapy ◽

Large Breast ◽

Significant Difference ◽

Mean Lung Dose ◽

The Impact ◽

Radiotherapy Treatment

AbstractPurposeTo explore the impact of breast size on mean lung dose (MLD) for patients receiving breast radiotherapy.MethodologyChest wall separation (CWS), volume of tissue receiving 95% isodose and MLD were measured on 80 radiotherapy treatment plans of patients receiving tangential radiotherapy treatment to the whole breast. Breast size was categorised as small (CWS<25 cm and planned target volume (PTV)<1,500 cm3) and large (CWS>25 cm and PTV>1500 cm3). Pearson’s correlation and independent sample t-test were used to analyse data.ResultsMLD was not affected by CWS (r=−0·13, p=0·24) nor volume of tissue receiving 95% isodose (r=−0·08, p=0·49). Significant variation between small and large breasts was noted for CWS (t=8·24, p=0·00) and volume of tissue receiving 95% isodose (t=5·68, p=0·00). No significant variation was noted between small and large breast for MLD (t=−0·26, p=0·80) and between left and right breasts for CWS (t=1·42, p=0·16) and volume of tissue receiving 95% isodose (t=−1·08, p=0·28). Significant difference between left (18–808 cGy) and right breast (325–365 cGy) was demonstrated for MLD (t=3·03, p=0·00).ConclusionThis study demonstrated lack of correlation between breast size and MLD. Further research is recommended for justification of alternative techniques for this subgroup of patients to provide optimised radiotherapy delivery.

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The Dosimetric and Temporal Effects of Respiratory-Gated, High-Dose-Rate Radiation Therapy in Patients With Lung Cancer

Technology in Cancer Research & Treatment ◽

10.1177/1533033818816072 ◽

2018 ◽

Vol 18 ◽

pp. 153303381881607 ◽

Cited By ~ 1

Author(s):

Ouided Rouabhi ◽

Brandie Gross ◽

John Bayouth ◽

Junyi Xia

Keyword(s):

Lung Cancer ◽

Radiation Therapy ◽

Dose Rate ◽

Treatment Time ◽

High Dose Rate ◽

High Dose ◽

Lung Dose ◽

Treatment Delivery ◽

Treatment Plans ◽

Mean Lung Dose

Purpose: To evaluate the dosimetric and temporal effects of high-dose-rate respiratory-gated radiation therapy in patients with lung cancer. Methods: Treatment plans from 5 patients with lung cancer (3 nongated and 2 gated at 80EX-80IN) were retrospectively evaluated. Prescription dose for these patients varied from 8 to 18 Gy/fraction with 3 to 5 treatment fractions. Using the same treatment planning criteria, 4 new treatment plans, corresponding to 4 gating windows (20EX-20IN, 40EX-40IN, 60EX-60IN, and 80EX-80IN), were generated for each patient. Mean tumor dose, mean lung dose, and lung V20 were used to assess the dosimetric effects. A MATLAB algorithm was developed to compute treatment time. Results: Mean lung dose and lung V20 were on average reduced between −16.1% to −6.0% and −20.0% to −7.2%, respectively, for gated plans when compared to the corresponding nongated plans, and between −5.8% to −4.2% and −7.0% to −5.4%, respectively, for plans with smaller gating windows when compared to the corresponding plans gated at 80EX-80IN. Treatment delivery times of gated plans using high-dose rate were reduced on average between −19.7% (−0.10 min/100 MU) and −27.2% (−0.13 min/100 MU) for original nongated plans and −15.6% (−0.15 min/100 MU) and −20.3% (−0.19 min/100 MU) for original 80EX-80IN-gated plans. Conclusion: Respiratory-gated radiation therapy in patients with lung cancer can reduce lung dose while maintaining tumor dose. Because treatment delivery during gated therapy is discontinuous, total treatment time may be prolonged. However, this increase in treatment time can be offset by increasing the dose delivery rate. Estimation of treatment time may be helpful in selecting patients for respiratory gating and choosing appropriate gating windows.

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417 poster FUNCTIONAL AVOIDANCE THROUGH MEAN LUNG DOSE AND BEAM ANGLES OPTIMIZATION FOR LUNG CANCER IMRT

Radiotherapy and Oncology ◽

10.1016/s0167-8140(11)70539-4 ◽

2011 ◽

Vol 99 ◽

pp. S166

Author(s):

J. St-Hilaire ◽

A. Dagnault ◽

C. Lavoie ◽

F. Beaulieu ◽

F. Morin ◽

...

Keyword(s):

Lung Cancer ◽

Lung Dose ◽

Mean Lung Dose

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Effect of Radiotherapy and Chemotherapy on Pulmonary Function After Treatment for Breast Cancer and Lymphoma: A Follow-Up Study

Journal of Clinical Oncology ◽

10.1200/jco.1999.17.10.3091 ◽

1999 ◽

Vol 17 (10) ◽

pp. 3091-3100 ◽

Cited By ~ 52

Author(s):

Jacqueline C.M. Theuws ◽

Sara H. Muller ◽

Yvette Seppenwoolde ◽

Stefan L.S. Kwa ◽

Liesbeth J. Boersma ◽

...

Keyword(s):

Breast Cancer ◽

Pulmonary Function ◽

Pulmonary Function Tests ◽

Three Dimensional ◽

Forced Expiratory Volume ◽

Lung Dose ◽

Alveolar Volume ◽

Initial Reduction ◽

The Mean ◽

Mean Lung Dose

PURPOSE: To determine the changes in pulmonary function tests (PFTs) 0 to 48 months after treatment for breast cancer and lymphoma. PATIENTS AND METHODS: The alveolar volume (VA), vital capacity, forced expiratory volume in 1 second, and corrected transfer factor of carbon monoxide (TL,COc) were measured in 69 breast cancer and 41 lymphoma patients before treatment and 3, 18, and 48 months after treatment with radiotherapy alone or radiotherapy in combination with chemotherapy (mechlorethamine, vincristine, procarbazine, prednisone, doxorubicin, bleomycin, vinblastine; cyclophosphamide, epidoxorubicin, fluorouracil; cyclophosphamide, thiotepa, carboplatin; cyclophosphamide, methotrexate, fluorouracil). The three-dimensional dose distribution in the lung of each patient was converted to the mean lung dose. Statistical analysis was used to evaluate the changes in PFT values over time in relation to age, sex, smoking, chemotherapy, and the mean lung dose. RESULTS: After an initial reduction in PFT values at 3 months, significant recovery was seen at 18 months for all patients. Thereafter, no further improvement could be demonstrated. Reductions in spirometry values and VA were related to the mean lung dose only (0.9% per Gy at 3 months and 0.4% per Gy mean dose at 18 months). TL,COc decreased 1.1% per Gy mean dose and additionally decreased 6% when chemotherapy was given after radiotherapy. Chemotherapy administered before radiotherapy reduced baseline TL,COc values by 8% to 21%. All patients showed an improvement of 5% at 18 months. CONCLUSION: On the basis of the mean lung dose and the chemotherapy regimen, the changes in PFT values can be estimated before treatment within 10% of the values actually observed in 72% to 85% of our patients with healthy lungs.

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