K. William Harter

Radiation dose pertubation at tissue-titanium dental interfaces in head and neck cancer patients

Purpose : To determine the dose perturbation effects at the tissue-metal implant interfaces in head and neck cancer patients treated with 6 MV and 10 MV photon beams. Methods and Materials : Phantom measurements were performed to investigate the magnitude of dose perturbation to the tissue adjacent to the titanium alloy implants with (100 μ and 500 μ thick) and without hydroxylapatite (HA) coating. Radiographic and radiochromic films were placed at the upper (and lower) surface of circular metal discs (diameter x thickness : 15 x 3.2, 48 x 3.2, 48 x 3.8 mm 2 ) in a solid water phantom and were exposed perpendicular to radiation beams. The dosimeters were scanned with automatic film scanners. Using a thin-window parallel-plate ion chamber, dose perturbation were measured for a 48 x 3.2 mm 2 disc. Results : At the upper surface of the tissue-dental implant interface, the radiographic data indicate that for 15 x 3.2 mm 2 uncoated, as well as 100 μ coated discs, dose perturbation is about +22.5% and +20.0% using 6 MV and 10 MV photon beams, respectively. For 48 x 3.2 mm 2 discs, these values basically remain the same. However, for 48 x 3.8 mm 2 discs, these values increase slightly to about +23.0% and +20.5% for 6 MV and 10 MV beams, respectively. For 48 x 3.2 mm 2 discs with 500 μ coating, dose enhancement is slightly lower than that obtained for uncoated and 100 μ coated discs for each beam energy studied. At the lower interface for 15 x 3.2 mm 2 and 48 x 3.2 mm 2 uncoated and 100 μ coated discs, dose reduction is similar and is about -13.5% and -9.5% for 6 MV and 10 MV beams, respectively. For 48 x 3.8 mm 2 discs, dose reduction is about -14.5% and -10.0% for 6 MV and 10 MV beams, respectively. For 48 x 3.2 mm 2 discs with 500 μ coating, the dose reduction were slightly higher than those for uncoated and 100 μ coated discs. Conclusions : For the beam energies studied, dose enhancement is slightly larger for the lower energy beam. The results of dose perturbation were similar for 100 μ coated and uncoated discs. These results were slightly lower for the 500 μ coated discs but are not clinically significant. The dosimetry results obtained from radiochromic films were similar to the ones obtained from radiographic film. The dose enhancement results obtained from ion chamber dosimetry are higher than those obtained from film dosimetry. The ion chamber data represent the data at true tissue-titanium interface, whereas the ones obtained from film dosimetry represent the data at film-titanium interface.

Planned neck dissection for advanced primary head and neck malignancy treated with organ preservation therapy: disease control and survival outcomes.

The role of planned neck dissection after organ preservation therapy with radiotherapy or chemotherapy/radiotherapy for advanced head and neck cancers presenting with clinically positive neck disease is still being elucidated. The aim of this study is to review the outcomes of such patients treated by organ preservation therapy at our institution.

Air cavity effects on the radiation dose to the larynx using Co-60, 6 MV, and 10 MV photon beams

PURPOSEnTo determine the perturbation effect in the surface layers of lesions located in the air-tumor tissue interface of larynx using 60Co, 6 MV, and 10 MV photon beams.nnnMETHODS AND MATERIALSnThermoluminescent dosimeters (TLDs), were embedded at 16 measurement locations in slab no. 8 of a humanoid phantom and exposed to two lateral-opposed beams using standard small 7 x 7 cm fields. Similarly, radiographic and radiochromic films were placed between slabs no. 7 and no. 8 of the humanoid phantom and exposed to two lateral-opposed radiation beams. The dosimeters were irradiated with 60Co, 6 MV, and 10 MV photon beams. Computer tomography (CT) treatment planning without inhomogeneity correction was performed.nnnRESULTSnAt the tissue-air interface, the average measured percentage dose (% dosem) is about (108.7 +/- 4.8)% with TLD data, (96.8 +/- 2.5)% with radiographic film data, and (100.8 +/- 4.9)% with radiochromic film data. Similarly, in the central part of the cavity, the % dosem is (98.4 +/- 3.1)% with TLD data, (94.3 +/- 3.3)% with radiographic film data, and (91.7 +/- 5.0)% with radiochromic film data. Using the CT-based generated dose distribution (without inhomogeneity correction), the average calculated percentage dose (% dosec) is (98.7 +/- 1.0)% at the tissue-air interface and 98% in the central part of the air cavity.nnnCONCLUSIONnFor the beam energies studied, the variation from the % dosem at the tissue-air interface for a given dosimetry technique is relatively small [< 5% (TLD), < 3% (radiographic), and < 5% (radiochromic)] and therefore should not be significant in clinical settings. The variation from the % dosem at the tissue-air interface is more significant for lower energies [8% (60Co), 7.3% (6 MV)]. This variation is about 4.3% for 10 MV photon beam, therefore, while our institutional practice favors lower energy (60Co to 6 MV) for node-negative glottic cancers, physical/dosimetric evidence offers no disadvantage to the use of higher energy photons.

Quercetin as a Modulator of the Cellular Neoplastic Phenotype

Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is a widely distributed plant-derived flavonoid present in most vegetables and fruits, and it is therefore a common component of the human diet.1 Quercetin has been shown to exert multiple biochemical effects in mammalian cells, including the increase of cAMP levels,2 the inhibition of enzymatic activities such as protein kinase C,3,4 protein tyrosine kinases,5–7 and cAMP and cGMP phosphodiesterases,8,9 as well as the interaction with estrogen type II binding sites.10 These biological actions of quercetin may explain its predominantly inhibitory effect of tumor-derived cell lines,10–14 and its ability to arrest tumor cells in the G1 phase13,15 or, less frequently, in the G2 -M phase16 of the cell cycle. Although some reports17,18 indicate that quercetin could be carcinogenic under certain experimental conditions, the overwhelming evidence demonstrating its ability to inhibit the growth of tumor cells identifies quercetin as an anticarcinogenic phytochemical. Furthermore, the dosage of quercetin could be easily modified in the human diet to attain the appropriate levels for optimum cancer chemopreventive action.

Effect of multimodality treatment on overall survival for patients with metastatic or recurrent HPV-positive head and neck squamous cell carcinoma.

The optimal treatment for patients with recurrent human papillomavirus (HPV)‐positive head and neck cancer is poorly understood.

Effects of beam spoiler on radiation dose for head and neck irradiation with 10-MV photon beam

PURPOSEnTo determine the effects of a lucite beam spoiler on the dose distribution to points inside and outside the primary beam for head and neck irradiation with a 10-MV photon beam.nnnMETHODS AND MATERIALSnBuild-up and depth-dose measurements were performed with a parallel-plate ionization chamber for 5 x 5, 10 x 10, and 15 x 15-cm field sizes using lucite spoilers with two different thicknesses at two different lucite-to-skin distances (LSD) for a 10-MV x-ray beam. Corrections were applied to account for finite chamber size. Beam profiles and isodose curves were obtained at several depths using film dosimetry. Beam uniformity was determined from uniformity indices. Peripheral doses (PD) were measured at the surface and at 1.5- and 2.5-cm depths using film dosimetry and a parallel-plate ionization chamber. Measurement points were positioned at the edge of a 10 x 10-cm field and at distances extending to 5.0 cm away. The treatment planning data for the 10-MV x-ray beam were modified to account for the effects of the beam spoiler when treating head and neck patients.nnnRESULTSnThe spoiler increased the surface and build-up dose and shifted the depth of maximum dose toward the surface. With a 10-MV x-ray beam and a 1.2-cm-thick lucite at 15 cm LSD, a build-up dose similar to a 6-MV x-ray beam was achieved. The beam uniformity was altered at shallow depths. The peripheral dose was enhanced particularly at the surface and at the points close to the beam edge. The effects of the beam spoiler on beam profile and PD were reduced with increasing depths.nnnCONCLUSIONnThe lucite spoiler allowed use of a 10-MV x-ray beam for head and neck treatment by yielding a build-up dose similar to that of a 6-MV x-ray beam while maintaining skin sparing. The increase in PD was at superficial depths and was reduced at points away from the edge; therefore, it is clinically nonsignificant. Spoiling the 10-MV x-ray beam resulted in treatment plans that maintained dose homogeneity without the consequence of increased skin reaction or treatment volume underdose for regions near the skin surface.

Limitations of reduced-field irradiated volume and technique in conventional radiation therapy of prostate cancer: Implications for conformal 3-D treatment

In order to define technical limitations of conventional external beam irradiation for clinically localized prostate cancer, we evaluated the impact of several reduced‐field treatment factors, such as reduced‐field (RF) irradiated volume, RF technique, photon energy of treatment, and dose on survival endpoints and local control in a retrospective series. Several survival endpoints, such as disease‐specific survival, freedom from relapse survival, biochemical no‐evidence of disease (bNED) survival, and local control were associated with several treatment variables using univariate and multivariate analyses in 329 patients. Reduced‐field technique appeared to predict survival outcome, with patients treated by bilateral 120° arcs faring less well than those treated by full 360° rotational fields. The irradiated volume of the reduced‐field was also significantly associated with survival outcome, with patients treated with smaller volumes faring less well. Local failure rates also appeared increased, although not statistically, in patients treated with smaller RF sizes. In an attempt to explain these detected deficiencies, dose‐volume histograms for prostate coverage were created for a small sample of patients. The deficiencies related to small reduced‐field volume appeared to be largely attributable to poor dosimetric coverage of the prostate. These results underscore the limitations of conventional external beam treatment for prostate carcinoma when conventional techniques are employed, particularly if small reduced fields are used, and further supports the development of improved treatment techniques, such as conformal irradiation, as alternatives. Int. J. Cancer (Radiat. Oncol. Invest.) 90:265–274, 2000.

Osteosarcoma and the Less Common Sarcomas of Childhood

Osteosarcoma is the second most common primary tumor of bone after plasmacytoma (myeloma) (Dahlin and Unni 1986). Within the pediatric age group, it is the most common primary bone tumor (Dahlin and Unni 1986; Lichtenstein 1977; Jaffe 1958). According to Dahlin and Unni, the sine qua non for histopathologic definition of osteosarcoma is the presence of proliferating malignant cells producing an osteoid substance or material histologically indistinguishable therefrom (Dahlin and Unni 1986). While the majority of osteosarcomas are primary idiopathic neoplasms occurring in the first two and a half decades, they may also arise spontaneously against a background of Paget’s disease of bone or as a consequence of therapeutic radiation for other tumors. In the Mayo Clinic series (Dahlin and Unni 1986), however, no patient developed osteosarcoma from Paget’s disease prior to the age of 30, thus excluding this etiology from discussion in the context of childhood. While the long latency period for radiation-associated osteosarcoma, 15.1 years in the Mayo Clinic series (Dahlin and Unni 1986), generally places the clinical presentation of such secondary tumors beyond the pediatric age group, enough cases are the apparent consequence of radiation in childhood to warrant further discussion (vide infra) (Dahlin et al. 1970; Nascimento et al. 1979; Hutter et al. 1962; Johnson and Dahlin 1959).

SP211 – Cyberknife treatment of carotid body tumors: A retrospective review

Kenneth Newkirk, MD Department of Otolaryngology—Head and Neck Surgery, Georgetown University Hospital Email: newkirka@gunet.georgetown.edu Website: www.georgetownuniversityhospital.org BACKGROUND: Paragangliomas, or glomus body tumors, are rare neoplasms of the head and neck which arise from paraganglionic tissue of mesodermal origin. Carotid body tumors are the most common paragangliomas of the head and neck and arise from the chemoreceptor cells at the carotid bifurcation. Surgical resection has been a mainstay of treatment for carotid body tumors, but significant morbidity can accompany the extirpation should the sacrifice of vital surrounding structures be unavoidable. Though there is limited data regarding the use of radiation therapy in the treatment of carotid body tumors, the safety and efficacy of the treatment has been demonstrated in small case series.

Epithelial Carcinomas in the Child

Malignancies derived from epithelial tissues account for the overwhelming majority of tumors in the adult population (American Cancer Society 1991). Such cancers are extremely rare in the pediatric age group (Young et al. 1981), representing less than 5% of all childhood malignancies. The infrequency with which such carcinomas are encountered in patients less than 18 years of age has thus far precluded prospective, systematic evolution of therapy. In general, treatment strategies are adapted from those in use for adults. Etiologic factors in childhood cancer include genetic predisposition (Sherlock et al. 1975; Reed and Neel 1955; McKusick 1964; Bussey 1970; Stemper et al. 1975; Haggitt and Pitcock 1970; Lynch et al. 1973), environmental factors and exposures (Correa and Haenszel 1978; Howell 1975; Wynder and Shigematsu 1967; Pratt and George982; Prati et al. 1977; Odone et al. 1982; Rao et al. 1985; Caldwell et al. 1981), ionizing radiation (Duffy and Fitzgerald 1950; Fjalling et al. 1986; Winship and Rosvoll 1961), and possibly Epstein-Barr virus (Klein et al. 1974; Huang et al. 1978; Henle and Henle 1976; Naegele et al. 1982). Potential causation is, of course, inapparent in many cases. When identified, such risk factors do not appear to have an influence upon clinical outcome, other than perhaps mitigating toward earlier diagnosis in those patients with recognizable clinical syndromes which put them at increased risk for malignancy.