Set-up errors in head and neck cancer treated with IMRT technique assessed by cone-beam computed tomography: a feasible protocol.

PURPOSE: To investigate set-up errors, suggest the adequate planning target volume (PTV) margin and image-guided radiotherapy frequency in head and neck (H&N) cancer treated with intensity-modulated radiotherapy (IMRT) assessed by kV cone-beam computed tomography (CBCT). METHODS: We analyzed 360 CBCTs in 60 patients with H&N cancer treated with IMRT. The target delineation was contoured according to ICRU62. PTVs were generated by adding a 3-5 mm margin in all directions to the respective clinical target volumes. The kV CBCT images were obtained at first three days of irradiation and weekly thereafter. The overall mean displacement, range, systematic (∑) and random (σ) errors were calculated. Adequate PTV margins were calculated according to the van Herk formula (2.5∑ + 0.7r). RESULTS: The mean of set-up errors was less than 2 mm in any direction. The overall frequency of set-up displacements greater than 3 mm was 3.9% in medial-lateral (ML) direction, 8% in superior-inferior (SI) direction, and 15.5% in anterior-posterior (AP) direction. The range of translations shifts was 0-9 mm in ML direction, 0-5 mm in SI direction and 0-10 mm in AP direction, respectively. After systematic set-up errors correction, the adequate margin to overcome the problem of set-up errors was found to be less than 3 mm. CONCLUSION: Image-guided kV CBCT was effective for the evaluation of set-up accuracy in H&N cancer. The kV CBCT at first three fractions and followed-by weekly appears adequate for reducing significantly set-up errors in H&N cancer treated with IMRT technique. Finally, 3-5 mm PTV margins appear adequate and safe to overcome the problem of set-up errors.

Single-fraction flattening filter-free volumetric modulated arc therapy for lung cancer: Dosimetric results and comparison with flattened beams technique.

PURPOSE: To report on single-fraction stereotactic body radiotherapy (RT) (SBRT) with flattening filter (FF)-free (FFF) volumetric modulated arc therapy (VMAT) for lung cancer and to compare dosimetric results with VMAT with FF. METHODS AND MATERIALS: Overall, 25 patients were treated with 6-MV FFF VMAT (Varian TrueBeam STx LINAC) to a prescribed dose of 24Gy in a single fraction. Treatment plans were recreated using FF VMAT. Dose-volume indices, monitor units (MU), and treatment times were compared between FFF and FF VMAT techniques. RESULTS: Dose constraints to PTV, spinal cord, and lungs were reached in FFF and FF plans. In FFF plans, average conformity index was 1.13 (95% CI: 1.07 to1.38). Maximum doses to spinal cord, heart, esophagus, and trachea were 2.9Gy (95% CI: 0.4 to 6.7Gy), 0.8Gy (95% CI: 0 to 3.6Gy), 3.3Gy (95% CI: 0.02 to 13.9Gy), and 1.5Gy (95% CI: 0 to 4.9Gy), respectively. Average V7Gy, V7.4Gy, and mean dose to the healthy lung were 126.5cc (95% CI: 41.3 to 248.9cc), 107.3cc (95% CI: 18.7 to 232.8cc), and 1.1Gy (95% CI: 0.3 to 2.2Gy), respectively. No statistically significant differences were found in dosimetric results and MU between FF and FFF treatments. Treatment time was reduced by an average factor of 2.31 (95% CI: 2.15 to 2.43) from FF treatments to FFF, and the difference was statistically significant. CONCLUSIONS: FFF VMAT for lung SBRT provides equivalent dosimetric results to the target and organs at risk as FF VMAT while significantly reducing treatment time.

Stereotactic body radiotherapy of bone metastases in oligometastatic disease: prognostic factors of oncologic outcomes.

BACKGROUND: To evaluate the safety of stereotactic body radiotherapy (SBRT) of bone metastases in oligometastatic disease and to investigate prognostic factors of local control (LC), progression/disease-free survival (PDFS), and overall survival (OS). METHODS: Eligibility criteria were number of metastates ≤5, controlled primary tumor without evidence of progression under systemic therapy, exclusion of surgery, and no previous radiotherapy of the lesion of interest. Oligometastatic status was classified into only bone (BOD) and outside bone disease (OBOD), whereas SBRT was delivered to bone lesions using 2 different schedules: 24 Gy/1 fraction or 27 Gy/3 fractions. A positron emission tomography study of the lesion of interest was performed at baseline and at 3 months after SBRT to evaluate metabolic response according to European Organization for Research and Treatment of Cancer (EORTC) criteria. A Cox regression model was used for univariate and multivariate analysis. RESULTS: Between January 2010 and December 2013, 40 patients were enrolled. Only 1 patient experienced severe late toxicity (radiation-related fracture). Local control was longer among responders' than nonresponders' lesions (94.2% and 91.2% versus 63% and 35% at 1 and 2 years, respectively) (p = 0.004; hazard ratio = 9.958). The multivariate analysis of PDFS showed a significant correlation with planning target volume (PTV) size (p = 0.003) and oligometastatic status (p = 0.002). The multivariate analysis of OS confirmed a statistically significant value of the oligometastatic status (p = 0.002) and a significant trend for PTV size (p = 0.065). CONCLUSIONS: Stereotactic body radiotherapy is safe with a low incidence of severe toxicity. Positron emission tomography response was a strong prognostic factor of LC whereas BOD status and small PTV size could identify a subset of oligometastatic patients at better prognosis.

[(18)F]Choline PET/CT and stereotactic body radiotherapy on treatment decision making of oligometastatic prostate cancer patients: preliminary results.

BACKGROUND: A new entity of patients with recurrent prostate cancer limited to a small number of active metastatic lesions is having growing interest: the oligometastatic patients. Patients with oligometastatic disease could eventually be managed by treating all the active lesions with local therapy, i.e. either surgery or ablative stereotactic body radiotherapy. This study aims to assess the impact of [(18)F]Choline ([(18)F]FMCH) PET/CT and the use stereotactic body radiotherapy (SBRT) in patients (pts) with oligometastatic prostate cancer (PCa). METHODS: Twenty-nine pts with oligometastatic PCa (≤3 synchronous active lesions detected with [(18)F]FMCHPET/CT) were treated with repeated salvage SBRT until disease progression (development of > three active synchronous metastases). Primary endpoint was systemic therapy-free survival measured from the baseline [(18)F]FMCHPET/CT. RESULTS: A total of 45 lesions were treated with SBRT. After a median follow-up of 11.5 months (range 3-40 months), 20 pts were still in the study and did not receive any systemic therapy. Nine pts started systemic therapy, and the median time of the primary endpoint was 39.7 months (CI 12.20-62.14 months). No grade 3 or 4 toxicity was recorded. CONCLUSIONS: Repeated salvage [(18)F]FMCHPET/CT-guided SBRT is well tolerated and could defer the beginning of systemic therapy in selected patients with oligometastatic PCa.