Poor baseline pulmonary function may not increase the risk of radiation-induced lung toxicity

PURPOSE

Poor pulmonary function (PF) is often considered a contraindication to definitive radiation therapy for lung cancer. This study investigated whether baseline PF was associated with radiation-induced lung toxicity (RILT) in patients with non-small cell lung cancer (NSCLC) receiving conformal radiation therapy (CRT).

METHODS AND MATERIALS

NSCLC patients treated with CRT and tested for PF at baseline were eligible. Baseline predicted values of forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), and diffusion capacity of lung for carbon monoxide (DLCO) were analyzed. Additional factors included age, gender, smoking status, Karnofsky performance status, coexisting chronic obstructive pulmonary disease (COPD), tumor location, histology, concurrent chemotherapy, radiation dose, and mean lung dose (MLD) were evaluated for RILT. The primary endpoint was symptomatic RILT (SRILT), including grade ≥2 radiation pneumonitis and fibrosis.

RESULTS

There was a total of 260 patients, and SRILT occurred in 58 (22.3%) of them. Mean FEV1 values for SRILT and non-SRILT patients were 71.7% and 65.9% (P=.077). Under univariate analysis, risk of SRILT increased with MLD (P=.008), the absence of COPD (P=.047), and FEV1 (P=.077). Age (65 split) and MLD were significantly associated with SRILT in multivariate analysis. The addition of FEV1 and age with the MLD-based model slightly improved the predictability of SRILT (area under curve from 0.63-0.70, P=.088).

CONCLUSIONS

Poor baseline PF does not increase the risk of SRILT, and combining FEV1, age, and MLD may improve the predictive ability.

Influence of rotations on dose distributions in spinal stereotactic body radiotherapy (SBRT)

PURPOSE

To evaluate the impact of rotational setup errors on dose distribution in spinal stereotactic body radiotherapy (SBRT).

METHODS AND MATERIALS

Thirty-nine cone beam computed tomography (CBCT) scans from 16 SBRT treatment courses were analyzed. Alignment (including rotation) to the treatment planning computed tomography was performed, followed by translational alignment that reproduced the actual positioning. The planned fluence was then applied to determine the delivered dose to the targets and organs at risk.

RESULTS

The mean planning target volume (PTV) was 71.01 mL (SD +/- 60.05; range, 22.62-250.65 mL). Prescribed dose (to the 62-82% isodose) was 14-30 Gy in one to six fractions. The average rotational displacements were 0.38 +/- 1.21, 1.12 +/- 1.82, and -0.51 +/- 2.0 degrees with maximal rotations of -4.29, 5.76, and -6.64 degrees along the x (pitch), y (yaw), and z (roll) axes, respectively. PTV coverage changed by an average of -0.07 Gy (SD +/- 0.20 Gy) between the rotated and the original plan, representing 0.92% of prescription dose (SD +/- 2.65%). For the spinal cord, planned with 2-mm expansion to create a planning organ at risk volume (PRV), the difference in minimum dose to the upper 10% of the PRV volume was 0.03 +/- 0.3 Gy (maximum, 0.9 Gy). Other organs at risk saw insignificant changes in dose.

CONCLUSIONS

PRV expansion generally assures safe treatment delivery in the face of typically encountered rotations. Given the variability of delivered dose within this expansion for certain cases, caution should be taken to properly interpret doses to the cord when considering clinical dose limits.

Phase II trial of high-dose conformal radiation therapy with concurrent hepatic artery floxuridine for unresectable intrahepatic malignancies

PURPOSE

A phase II trial was conducted to determine if high-dose radiation with concurrent hepatic arterial floxuridine would improve survival in patients with unresectable intrahepatic malignancies.

PATIENTS AND METHODS

Three-dimensional conformal high-dose radiation therapy was delivered concurrently with hepatic arterial floxuridine in 128 patients. The radiation dose was based on a normal-tissue complication probability model and subjected the patient to an estimated maximum risk of radiation-induced liver disease of 10% to 15%. The study design provided more than 80% power to detect a two-fold increase in median survival compared with historical controls at a 5% significance level.

RESULTS

The median radiation dose delivered was 60.75 Gy (1.5-Gy fractions bid). At a median follow-up time of 16 months (26 months in patients who were alive) the median survival was 15.8 months (95% CI, 12.6 to 18.3 months), significantly longer than in the historical control. The actuarial 3-year survival was 17%. The total dose was the only significant predictor of survival. Primary hepatobiliary tumors had a significantly greater tendency to remain confined to the liver than did colorectal cancer metastases. Overall toxicity was acceptable, with 27 patients (21%) and 11 patients (9%) developing grade 3 and 4 toxicity, respectively, and one treatment-related death.

CONCLUSION

The results suggest that, compared with historical controls, high-dose focal liver irradiation with hepatic artery floxuridine prolongs survival in patients with unresectable chemotherapy-refractory metastatic colorectal cancer and primary hepatobiliary tumors. This provides a rationale for intensification of local therapy for unresectable hepatobiliary cancers and integration of this regimen with newer systemic therapy for patients with colorectal cancer.

Long-term results of high-dose conformal radiotherapy for patients with medically inoperable T1–3N0 non–small-cell lung cancer: Is low incidence of regional failure due to incidental nodal irradiation?

PURPOSE

To report the results of high-dose conformal irradiation and examine incidental nodal irradiation and nodal failure in patients with inoperable early-stage non-small-cell lung cancer (NSCLC).

METHODS AND MATERIALS

This analysis included patients with inoperable CT-staged T1-3N0M0 NSCLC treated on our prospective dose-escalation trial. Patients were treated with radiation alone (total dose, 63-102.9 Gy in 2.1-Gy daily fractions) with a three-dimensional conformal technique without intentional nodal irradiation. Bilateral highest mediastinal and upper/lower paratracheal, prevascular and retrotracheal, sub- and para-aortic, subcarinal, paraesophageal, and ipsilateral hilar regions were delineated individually. Nodal failure and doses of incidental irradiation were studied.

RESULTS

The potential median follow-up was 104 months. For patients who completed protocol treatment, median survival was 31 months. The actuarial overall survival rate was 86%, 61%, 43%, and 21% and the cause-specific survival rate was 89%, 70%, 53%, and 35% at 1, 2, 3, and 5 years, respectively. Weight loss (p = 0.008) and radiation dose in Gy (p = 0.013) were significantly associated with overall survival. In only 22% and 13% of patients examined did ipsilateral hilar and paratracheal (and subaortic for left-sided tumor) nodal regions receive a dose of > or = 40 Gy, respectively. Less than 10% of all other nodal regions received a dose of > or = 40 Gy. No patients failed initially at nodal sites.

CONCLUSIONS

Radiation dose is positively associated with overall survival in patients with medically inoperable T1-3N0 NSCLC, though long-term results remain poor. The nodal failure rate is low and does not seem to be due to high-dose incidental irradiation.

Evaluating the influence of setup uncertainties on treatment planning for focal liver tumors

PURPOSE

A mechanism has been developed to evaluate the influence of random setup variations on dose during treatment planning. The information available for studying these factors shifts from population-based models toward patient-specific data as treatment progresses and setup measurements for an individual patient become available. This study evaluates the influence of population as well as patient-specific setup distributions on treatment plans for focal liver tumors.

METHODS AND MATERIALS

Eight patients with focal liver tumors were treated on a protocol that involved online setup measurement and adjustment, as well as ventilatory immobilization. Summary statistics from these three-dimensional conformal treatments yielded individual and population distributions of position at initial setup for each fraction. A convolution model for evaluation of the influence of random setup variation on calculated dose distributions has been previously described and investigated for application to focal liver radiotherapy by our department. Individual patient doses based on initial setup positions were calculated by convolving the calculated dose distribution with an anisotropic probability distribution function representing the individual patient's random variations. A separate convolution using population-averaged random variations was performed. Individual beam apertures were then adjusted to provide plans that ensured proper dose to the clinical target volume following convolution with population distributions, as well as individual patient position uncertainty models.

RESULTS

Individual patient setup distributions for the course of treatment had random setup variations (sigma) that ranged from 2.5 to 5.7 mm (left-right), 2.1 to 8.3 mm (anterior-posterior), and 4.1 to 10.8 mm (cranial-caudal). The population random components were 4.2 mm (left-right), 4.1 mm (anterior-posterior), and 7.0 mm (cranial-caudal) at initial setup. The initial static planned dose distribution overestimated the volume of liver irradiated to high doses, because inclusion of setup uncertainties generally blurred the resulting doses, shifting the higher-dose region of normal liver dose-volume histograms to lower doses. Furthermore, the population-based dose convolution tended to predict a higher risk of radiation damage to the liver (based on an in-house parameterization of the Lyman normal tissue complication probability model) than the individual patient calculations. For an individual plan, application of different individual random variations yielded change in effective volume differences with a 3% range. Plan adjustment to account for random setup variations generally resulted in a lower change in effective volume than initial planning using a planning target volume followed by calculation of delivered dose based on random offsets.

CONCLUSION

This study hints at the factors that most strongly influence planning of liver treatments taking into account geometric variations. Given a setup verification methodology that rapidly reduces systematic offsets, the importance of realistic incorporation of geometric variations as an initial step in treatment planning, as well as possible plan refinement, is demonstrated.

Evaluating changes in tumor volume using magnetic resonance imaging during the course of radiotherapy treatment of high-grade gliomas: Implications for conformal dose-escalation studies

OBJECTIVE

To determine whether changes in tumor volume occur during the course of conformal 3D radiotherapy of high-grade gliomas by use of magnetic resonance imaging (MRI) during treatment and whether these changes had an impact on tumor coverage.

METHODS AND MATERIALS

Between December 2000 and January 2004, 21 patients with WHO Grades 3 to 4 supratentorial malignant gliomas treated with 3D conformal radiotherapy (median dose, 70 Gy) were enrolled in a prospective clinical study. All patients underwent T1-weighted contrast-enhancing and T2-weighted and fluid-attenuated inversion recovery (FLAIR) imaging at approximately 1 to 2 weeks before radiotherapy, during radiotherapy (Weeks 1 and 3), and at routine intervals thereafter. All MRI scans were coregistered to the treatment-planning CT. Gross tumor volume (GTV Pre-Rx) was defined from a postoperative T1-weighted contrast-enhancing MRI performed 1 to 2 weeks before start of radiotherapy. A second GTV (GTV Week 3) was defined by use of an MRI performed during Week 3 of radiotherapy. A uniform 0.5 cm expansion of the respective GTV, PTV (Pre-Rx), and PTV (Week 3) was applied to the final boost plan. Dose-volume histograms (DVH) were used to analyze any potential adverse changes in tumor coverage based on Week 3 MRI.

RESULTS

All MRI scans were reviewed independently by a neuroradiologist (DGH). Two patients were noted to have multifocal disease at presentation and were excluded from analysis. In 19 cases, changes in the GTV based on MRI at Week 3 during radiotherapy were as follows: 2 cases had an objective decrease in GTV (> or =50%); 12 cases revealed a slight decrease in the rim enhancement or changes in cystic appearance of the GTV; 2 cases showed no change in GTV; and 3 cases demonstrated an increase in tumor volume. Both cases with objective decreases in GTV during treatment were Grade 3 tumors. No cases of tumor progression were noted in Grade 3 tumors during treatment. In comparison, three of 12 Grade 4 tumors had tumor progression, based on MRI obtained during Week 3 of radiotherapy. Median increase in GTV (Week 3) was 11.7 cc (range, 9.8-21.3). Retrospective DVH analysis of PTV (Pre-Rx) and PTV (Week 3) demonstrated a decrease in V(95%)(PTV volume receiving 95% of the prescribed dose) in those 3 cases.

CONCLUSIONS

Routine MR imaging during radiotherapy may be essential in ensuring tumor coverage if highly conformal radiotherapy techniques such as stereotactic boost and intensity-modulated radiotherapy are used in dose-escalation trials that utilize smaller treatment margins.