Investigating the Clinical Aspects of Using CT vs. CT-MRI Images during Organ Delineation and Treatment Planning in Prostate Cancer Radiotherapy

In order to apply highly conformal dose distributions, which are characterized by steep dose fall-offs, it is necessary to know the exact target location and extension. This study aims at evaluating the impact of using combined CT-MRI images in organ delineation compared to using CT images alone, on the clinical results. For 10 prostate cancer patients, the respective CT and MRI images at treatment position were acquired. The CTV was delineated using the CT and MRI images, separately, whereas bladder and rectum were delineated using the CT images alone. Based on the CT and MRI images, two CTVs were produced for each patient. The mutual information algorithm was used in the fusion of the two image sets. In this way, the structures drawn on the MRI images were transferred to the CT images in order to produce the treatment plans. For each set of structures of each patient, IMRT and 3D-CRT treatment plans were produced. The individual treatment plans were compared using the biologically effective uniform dose ([Formula: see text]) and the complication-free tumor control probability ( P+) concepts together with the DVHs of the targets and organs at risk and common dosimetric criteria. For the IMRT treatment, at the optimum dose level of the average CT and CT-MRI delineated CTV dose distributions, the P+ values are 74.7% in both cases for a [Formula: see text] of 91.5 Gy and 92.1 Gy, respectively. The respective average total control probabilities, PB are 90.0% and 90.2%, whereas the corresponding average total complication probabilities, PI are 15.3% and 15.4%. Similarly, for the 3D-CRT treatment, the average P+ values are 42.5% and 46.7%, respectively for a [Formula: see text] of 86.4 Gy and 86.7 Gy, respectively. The respective average PB values are 80.0% and 80.6%, whereas the corresponding average PI values are 37.4% and 33.8%, respectively. For both radiation modalities, the improvement mainly stems from the better sparing of rectum. According to these results, the expected clinical effectiveness of IMRT can be increased by a maximum Δ P+ of around 0.9%, whereas of 3D-CRT by about 4.2% when combined CT-MRI delineation is performed instead of using CT images alone. It is apparent that in both IMRT and 3D-CRT radiation modalities, the better knowledge of the CTV extension improved the produced dose distribution. It is shown that the CTV is irradiated more effectively, while the complication probabilities of bladder and rectum, which is the principal organs at risk, are lower in the CT-MRI based treatment plans.

Dosimetric evaluation of a new collimator insert system for stereotactic radiotherapy

The prototype of a stereotactic collimator set developed in our department is evaluated for clinical use. This set consists of three cylindrical blocks mounted on a tray which slides in the wedge insert of a Siemens Primus accelerator. Each block has a collimating hole along its long axis to produce radiation fields of circular cross-section at the isocentre plane with diameters of 15 mm, 20 mm and 25 mm. Different geometric and dosimetric quality assurance tests were performed and results are found within the limits set for stereotactic radiotherapy. Dosimetry results measured using Kodak EDR-2 radiographic film and a pinpoint ion chamber also show good agreement with corresponding results calculated by Monte Carlo simulation of the linear accelerator head and the collimators. Measured dosimetry data were used to adapt a conventional PLATO treatment planning system for stereotactic radiotherapy using the prototype collimator set. Treatment planning system calculations and film measurements for treatment of an intracranial lesion in an anthropomorphic head phantom using coplanar 180 degrees arcs are compared and found to agree within 2 mm. This supports the accuracy of dose delivery using the prototype stereotactic collimators. Despite their increased penumbra (2.5-3.5 mm relative to 2-2.5 mm for commercially available collimators) the ease of construction makes the proposed stereotactic collimators an interesting alternative for accomplishing cost effective stereotactic treatments.

Stent therapy for malignant superior vena cava syndrome: should be first line therapy or simple adjunct to radiotherapy

The goal of this paper is to present our experience with superior vena cava (SVC) stenting, as first line procedure for immediate relief, in patients with malignancy, and its potential influence in the subsequent radiotherapy (XRT). Over a 1-year period, 18 patients with SVC syndrome due to severe stenosis secondary to mediastinal malignancy were referred for stent insertion. A SVC score was used to measure treatment effectiveness. Stent insertion had been successful in 18/18 patients (technical success 100%). All patients experienced symptomatic relief within few hours of the procedure. There were no major complications. In all patients we were able to start radiotherapy (XRT) the next day, after stenting according to our new institutional protocol. All patients were able to comply with the XRT program, perfectly well.

CONCLUSIONS

SVC stenting provides immediate significant relief of the very annoying SVC syndrome symptoms, thus facilitating excellent compliance of all the patients to the subsequently XRT protocols. We strongly recommend SVC stenting as first line procedure, in patients with SVC syndrome due to malignancy prior to radiotherapy.

Oral pseudomembranous candidiasis, herpes simplex virus-1 infection, and oral mucositis in head and neck cancer patients receiving radiotherapy and granulocyte-macrophage colony-stimulating factor (GM-CSF) mouthwash

Oral pseudomembranous candidiasis (OPC) was evaluated in 61 patients receiving head and neck radiotherapy (RT). Herpes simplex virus-1 (HSV-1) reactivation was also investigated in 14 patients. According to the agreed protocol, granulocyte-macrophage colony-stimulating factor (GM-CSF) mouthwash was administered in 46 patients with radiation-induced ulcers. Candidiasis was diagnosed in 31 patients. Candida albicans was the most frequent isolate. Multiple Candida species were isolated from the lesions of four patients. Concurrent candidiasis and radiation-induced ulcers were observed in 17 patients. Viral culture and the polymerase chain reaction disclosed the presence of HSV-1 in five patients. Twenty of the 46 patients, with initial mucositis grade II and grade III, completed RT with mucositis grade I, indicating a beneficial effect of GMCSF mouthwash, although further controlled studies are necessary to verify that. In conclusion, OPC was an important infection in patients undergoing radiotherapy. The role of HSV-1 in oral mucositis during head and neck radiotherapy needs additional study.

A Monte Carlo investigation of the dosimetric characteristics of the VariSource 192Ir high dose rate brachytherapy source

An analytical Monte Carlo simulation code, incorporating in detail source construction and dimensions, was used to investigate the dosimetric characteristics of the VariSource 192Ir high dose rate brachytherapy source. Dose-rate constant, radial dose functions, and anisotropy functions, utilized in the AAPM Task Group 43 dose estimation formalism, were calculated with the source centered in a spherical water phantom of 30 cm in diameter. The results, which are in agreement with the corresponding data available in the literature, are compared to those obtained in our previous study for the widely used microSelectron 192Ir high dose-rate brachytherapy source. The dose-rate constant was found to be equal to 1.043 +/- 0.005 cGy h(-1) U(-1) for the VariSource, compared to a value of 1.116 +/- 0.006 cGy h(-1) U(-1) calculated for the microSelectron. Significant differences in the anisotropy of the two sources are observed only for polar angles close to their long axis and are due to their different dimensions.

A pilot study of the effect of granulocyte-macrophage colony-stimulating factor on oral mucositis in head and neck cancer patients during X-radiation therapy: a preliminary report

PURPOSE

To evaluate the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) in reduction of radiotherapy-induced oral mucositis.

METHODS AND MATERIALS

Seventeen patients who were going to be irradiated with a total dose of 50-70 Gy for head and neck malignancies were included in the study. After the second week of radiotherapy, with the experience of oral pain, GM-CSF 400 microg was administered locally, once a day, until completion of radiotherapy. Patients were evaluated weekly for mucosal reaction and functional impairment.

RESULTS

Three patients with gross and functional mucositis grade I after the second week, completed the planned radiotherapy showing mucositis grade I. Eleven patients who experienced, after 2 weeks of radiotherapy, mucositis grade II and III, presented after the third week with gross mucositis grade I and II and functional impairment grade I. One of these 11 patients was then lost to follow-up and the remaining 10 completed their planned radiotherapy having an almost asymptomatic mucositis grade I. The 15th patient with gross mucositis grade III after the 2 weeks of radiotherapy, had a 2-day interruption because of painful mucositis and then continued and completed radiotherapy with gross and functional mucositis grade I. The 16th patient with mucositis grade III after the second week, did not show any improvement, and completed her planned radiotherapy with mucositis grade III which finally healed after the administration of acyclovir. The last, 17th patient discontinued radiotherapy at the third week because of mucositis grade IV and severe ulceration in apposition to an extensive gold prosthesis.

CONCLUSION

The local administration of GM-CSF significantly reduced and almost healed radiation-induced oral mucositis in 14 of 17 patients during the radiotherapy, which was completed within the preplanned time and without any significant patient weight loss or functional impairment.

Chemotherapy of non small cell lung cancer. A prospectively randomized study of cisplatin-etoposide versus cisplatin-mitomycin-vinblastine

Based on preclinical studies showing synergism between cisplatin and etoposide, we randomized patients with non small cell lung cancer (NSCLC) to receive either the above combination (cisplatin 100 mg/m2 day 1, etoposide 130 mg/m2 days 1-3) or the combination of cisplatin-mitomycin-c and vinca drugs (MVP) (cisplatin 100 mg/m2, vinblastine 6 mg/m2, mitomycin 10 mg/m2 day 1), a regimen with a steady response rate. Partial responses were achieved in 12/44 (27%) of the cisplatin-etoposide group and in 11/43 (26%) of the MVR group. No difference in median survival could be demonstrated between the two groups (36 weeks versus 38 weeks). Myelotoxicity and alopecia were more severe in the cisplatin-etoposide group. Compared to international experience both regimens exhibited a relatively low response rate. It seems that for NSCLC new agents are required.

Computed tomography of ovarian carcinoma

Forty-seven patients with ovarian carcinoma were examined with computed tomography (CT). Fourteen were evaluated before laparotomy (group I), 25 following surgical treatment (group II), and 8 were followed by CT in the course, or following chemotherapy with or without radiation therapy (group III). CT provided accurate estimates of the size, shape and structure of the ovarian tumor in 8 patients in group I and contributed to diagnosis in 3 others. Primary ovarian tumors were incorrectly diagnosed in 3 cases. CT examination was valuable for detection of metastases in the mesenterium, omentum, peritoneum, abdominal organs and lymph nodes. The detection of small (1 cm diameter) metastatic implants on the peritoneal surface, omentum and liver capsule was facilitated by the presence of ascites. CT proved useful for patient follow-up, either after surgical treatment or when chemotherapy with or without radiation therapy was used.