RESUMO

Adenoid cystic carcinoma is a rare malignancy that usually originates in the salivary glands of the head and neck but has rarely been known to originate in the trachea. This histology has a predilection for perineural invasion and a tendency for both local and distant recurrences. While surgical resection is the mainstay of treatment of tracheal adenoid cystic carcinoma, tumor size, location, and patient comorbidities may preclude surgery, and the optimal nonsurgical management remains undefined. In the absence of locoregional lymph node metastases, we recommend highly conformal radiotherapy alone to a dose of 80 Gy. We report on two patients with unresectable disease who were treated with definitive radiotherapy: one using conventional photons and one treated with a combination of photon and proton beams. Both patients were treated to a dose of 80 Gy with acceptable toxicities and objective clinical and radiographic response. The patient treated with conventional photons has no evidence of recurrent disease at 5 years; the patient treated with protons has continued evidence of response without evidence of disease recurrence 11 months after treatment.

Assuntos

Carcinoma Adenoide Cístico/radioterapia , Radioterapia Conformacional/métodos , Neoplasias da Traqueia/radioterapia , Adulto , Carcinoma Adenoide Cístico/diagnóstico por imagem , Feminino , Seguimentos , Humanos , Pessoa de Meia-Idade , Fótons/uso terapêutico , Terapia com Prótons , Lesões por Radiação/etiologia , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Tomografia Computadorizada por Raios X , Neoplasias da Traqueia/diagnóstico por imagem

RESUMO

We report results of in-vivo light dosimetry of light fluence (rate) in human prostate during photodynamic therapy (PDT). Measurements were made in-vivo at the treatment wavelength (732nm) in 15 patients in three to four quadrants using isotropic detectors placed inside catheters inserted into the prostate. The catheter positions are determined using a transrectal ultrasound (TRUS) unit attached to a rigid template with 0.5-cm resolution. Cylindrical diffusing fibers with various lengths are introduced into the catheters to cover the entire prostate gland. For the last four patients, distributions of light fluence rate along catheters were also measured using a computer controlled step motor system to move multiple detectors to different distances (with 0.1 mm resolution). To predict the light fluence rate distribution, a kernel-based model was used to calculate light fluence rate using either (a) the mean optical properties (assuming homogeneous optical properties) for all patients or (b) using distributions of optical properties measured for latter patients. Standard deviations observed between the calculations and measurements were 56% and 34% for (a) and (b), respectively. The study shows that due to heterogeneity of optical properties significant variations of light fluence rate were observed both intra and inter prostates. However, if one assume a mean optical properties (µa = 0.3 cm-1, µs' = 14 cm-1), one can predict the light fluence rate to within a maximum error 200% for 80% of the cases and a mean error of 105%. To improve the prediction of light fluence rate further would require determination of distribution of optical properties.

RESUMO

Among the challenges to the clinical implementation of photodynamic therapy (PDT) is the delivery of a uniform photodynamic dose to induce uniform damage to the target tissue. As the photodynamic dose depends on both the local sensitizer concentration and the local fluence rate of treatment light, knowledge of both of these factors is essential to the delivery of uniform dose. In this paper, we investigate the distribution and kinetics of the photosensitizer motexafin lutetium (MLu, Lutrin®) as revealed by its fluorescence emission. Our current prostate treatment protocol involves interstitial illumination of the organ via cylindrical diffusing fibers (CDF's) inserted into the prostate though clear catheters. For planning and treatment purposes, the prostate is divided into 4 quadrants. We use one catheter in each quadrant to place an optical fiber-based fluorescence probe into the prostate. This fiber is terminated in a beveled tip, allowing it to deliver and collect light perpendicular to the fiber axis. Excitation light is provided by a 465 nm light emitting diode (LED) source coupled to a dichroic beamsplitter, which passes the collected fluorescence emission to a CCD spectrograph. Spectra are obtained before and after PDT treatment in each quadrant of the prostate and are analyzed via a linear fitting algorithm to separate the MLu fluorescence from the background fluorescence originating in the plastic catheter. A computer-controlled step motor allows the excitation/detection fiber to be moved along the catheter, building up a linear profile of the fluorescence emission spectrum of the tissue as a function of position. We have analyzed spectral fluorescence profiles obtained in 4 patients before and after MLu-mediated PDT. We find significant variation both within individual prostates and among patients. Within a single quadrant, we have observed the fluorescence signal to change by as much as a factor of 3 over a distance of 2 cm. Comparisons of pre- and post-PDT spectra allow a quantification treatment-induced photobleaching. Like the drug distribution, the extent of photobleaching varies widely among patients. In two cases, we observed bleaching of approximately 50% of the drug, while others exhibited negligible photobleaching.