Radiochromic film based dosimetry of image-guidance procedures on different radiotherapy modalities.

In this work we compare doses from imaging procedures performed on today's state-of-the-art integrated imaging systems using a reference radiochromic film dosimetry system. Skin dose and dose profile measurements from different imaging systems were performed using radiochromic films at different anatomical sites on a humanoid RANDO phantom. EBT3 film was used to measure imaging doses from a TomoTherapy MVCT system, while XRQA2 film was used for dose measurements from kilovoltage imaging systems (CBCT on 21eX and TrueBeam Varian linear accelerators and CyberKnife stereoscopic orthogonal imagers). Maximum measured imaging doses in cGy at head, thorax, and pelvis regions were respectively 0.50, 1.01, and 4.91 for CBCT on 21eX, 0.38, 0.84, and 3.15 for CBCT on TrueBeam, 4.33, 3.86, and 6.50 for CyberKnife imagers, and 3.84, 1.90, and 2.09 for TomoTherapy MVCT. In addition, we have shown how an improved calibration system of XRQA2 film can achieve dose uncertainty level of better than 2% for doses above 0.25 cGy. In addition to simulation-based studies in literature, this study provides the radiation oncology team with data necessary to aid in their decision about imaging frequency for image-guided radiation therapy protocols.

Optic gliomas: a retrospective analysis of 50 cases.

PURPOSE: Gliomas of the optic pathways are rare childhood central nervous system tumors. The treatment approach is controversial because of its rarity and the slow and unpredictable growth rates of these lesions. METHODS AND MATERIALS: We reviewed 50 patients with the diagnosis of optic pathway low-grade gliomas treated between January 1980 and December 1995 at King Faisal Specialist Hospital and Research Center, Saudi Arabia. Thirty-five patients presented with chiasmatic/hypothalamic (posterior tumors), and 15 with optic nerve gliomas with or without chiasmal involvement (anterior tumors). Evidence of neurofibromatosis was present in 18 patients. Twenty-nine patients underwent surgery (total or partial resection), and 12 of these received postoperative radiotherapy (RT). Sixteen patients were treated with primary RT. The radiation dose varied between 42 and 54 Gy (median dose 50). RESULTS: The overall actuarial survival rate was 87.5% at 5 years and 75% at 10 years, and the corresponding progression-free survival (PFS) rates were 69% and 62%. Patients with anterior tumors fared better than those with posterior tumors, with a 10-year PFS rate of 72% and 58%, respectively; the difference, however, was not statistically significant (p = 0.58). A PFS advantage was found in favor of patients with posterior tumors treated with RT (primary or postoperative) compared with no RT, with 5-year PFS rates of 68% vs. 42% (p = 0.03). This, however, did not translate into a survival advantage because of the success of salvage treatment. CONCLUSION: In multivariate analysis, age (<3 vs. >3 years) emerged as the only significant determinant for PFS with patients <3 years old faring worse (p = 0.03). Neurologic and endocrine dysfunction are significant problems that need to be addressed.

Localised Ewing sarcoma/PNET of bone--prognostic factors and international data comparison.

BACKGROUND: To determine if the distribution of prognostic factors accounted for the differences when the outcome for localised Ewing Sarcoma/PNET bone in Saudi Arabia was compared with results from countries with well developed health care systems. PROCEDURE: Retrospective analysis was undertaken of 163 consecutive patients of all ages, treated with radical intent at KFSHRC from 1975 to 1998. Standard chemotherapy was commenced in all patients. The local treatment modality was resection +/- radiation in 30% and radiation treatment alone in 67%. Size data were available for 51 patients treated from 1994 to 1998, inclusive. One third of these patients had tumors with volume >500 ml. RESULTS: Three year survival significantly increased with the year of diagnosis, 1975-1988 45%; 1989-1993 55%; and 1993-1998 63% (P = 0.006). Favorable prognostic factors were age < or =14 (P = 0.07); site, distal extremity, and skull (P = 0.08); and volume < or = 200 ml (P = 0.06). Secondary prognostic factors were response to induction chemotherapy, both histological, 100% necrosis, (P = 0.04) and clinical CR+PR, (P = 0.02). From 1994 to 1998, 3 year survival for tumors in the distal extremity and skull was 80% and for small tumors, < 200 ml, at any site was 82%. In comparison, the 3 year survival for patients with tumors at any other sites was 60%, and for tumors >200 ml, 55%. CONCLUSIONS: Overall survival progressively improved. From 1994 to 1998 the survival of patients with small tumors and/or favorable sites was similar to the best reported results. It was not possible to compare results by tumor size for large tumors, > 500 ml, due to the absence of data from elsewhere. A better staging system is required for the international comparison of results.