F. Pupillo

Determination of the correction factors for different ionization chambers used for the calibration of the helical tomotherapy static beam.

BACKGROUND AND PURPOSE To determine the machine-specific correction factors for three commercial ionization chambers (Exradin A1SL, PTW Semiflex and PTW PinPoint) to be applied in the dose calibration of a helical tomotherapy (HT) unit. MATERIALS AND METHODS Machine-specific reference (msr) conditions for HT unit involved a 10 × 5 cm(2) (IEC x×y) radiation field at 85 cm SSD with the ionization chamber (IC) positioned at 10 cm depth in Virtual Water. Each msr correction factor was determined using the formalism proposed by the AAPM Task Group 148 (i.e. k(Q[HT)(TG-51])) and was compared to direct calibration of the ICs against radiochromic films, calibrated in absolute dose at our institute, following the formalism proposed by the IAEA-AAPM joint committee (i.e. [Formula: see text] ). RESULTS TPR(20,10) values under HT msr conditions were 0.608, 0.608 and 0.615 corresponding to %dd(10)(x[HT)(Ref]) of 0.606, 0.606 and 0.613 for A1SL, Semiflex and PinPoint ICs, respectively. Based on these findings, k(Q[HT)(TG-51]) determination resulted 0.998±0.001, 0.998±0.001 and 0.991±0.002 for A1SL, Semiflex and PinPoint ICs, respectively. The [Formula: see text] correction factors obtained through direct calibration were 1.000±0.010, 1.004±0.007 and 0.998±0.006 for A1SL, Semiflex and PinPoint ICs, respectively. CONCLUSIONS Direct calibration of ICs versus radiochromic films provided correction factors equivalent to those obtained following the TG-148 formalism. This study showed that ICs calibrated for conventional linear accelerators can be used for the calibration of the static beam delivered by a HT unit taking into account the particular reference conditions.

Excellent survival regardless of disease stage in patients with advanced nasopharyngeal cancer.

Background We present our experience in assessing the feasibility and efficacy outcomes of intensified intensity-modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB) delivered to patients with nasopharyngeal carcinoma (NPC). Methods Between March 2009 and December 2014, 35 patients affected by advanced NPC with a median age of 53 years (range 11-77) were treated with definitive radiotherapy. Radiotherapy was delivered by helical tomotherapy with the SIB technique. The prescribed doses were 66 Gy to macroscopic disease, 60 Gy to high-risk subclinical disease, and 54 Gy to low-risk disease in 30 fractions. The daily SIB dose was 2.2 Gy to macroscopic disease. Results At the end of treatment 33 (94%) patients had obtained complete clearance of disease and 2 patients had died (1 of persistent disease after 3 months and 1 of cancer-unrelated causes after 4 months). At a median follow-up of 40 months (range 5-69), locoregional control rates at 2 and 4 years were 92.9% and 88.2%, respectively, and the overall survival after 4 years was 93.9%. The most significant acute toxicities were grade 2 and 3 mucositis (43%). No grade 3 and 4 late toxicities were observed; grade 2 xerostomia after 6 months from the end of treatment was reported in 11 patients; xerostomia toxicity decreased to grade 1 in 6/11 patients within 12 months. Conclusions These results show that intensified IMRT with SIB is an excellent strategy offering high local control rates for NPC patients with mild acute and late toxicity.

Long-term survival in a patient with head and neck paraganglioma treated with tailored modalities for 20 years: a case report

Aims and background Primary paragangliomas of nasal cavity and paranasal sinus are rare conditions that could show aggressive behavior with local recurrence and metastasis development. The diagnosis of malignancy is challenging because there are no available histopathologic criteria. In these cases, the prognosis is usually poor. Methods We report a case of a woman with malignant paranasal sinus paragangliomas. Results The patient was treated with several surgical approaches, radiotherapy, and medical therapy for different recurrences. Conclusions Despite the malignant behavior of the disease, this patient is still alive many years after first diagnosis.