Dosimetric characteristics of a MOSFET dosimeter for clinical electron beams

The fundamental dosimetric characteristics of commercially available metal oxide semiconductor field effect transistor (MOSFET) detectors were studied for clinical electron beam irradiations. MOSFET showed excellent linearity against doses measured using an ion chamber in the dose range of 20-630cGy. MOSFET reproducibility is better at high doses compared to low doses. The output factors measured with the MOSFET were within +/-3% when compared with those measured with a parallel plate chamber. From 4 to 12MeV, MOSFETs showed a large angular dependence in the tilt directions and less in the axial directions. MOSFETs do not show any dose-rate dependence between 100 and 600MU/min. However, MOSFETs have shown under-response when the dose per pulse of the beam is decreased. No measurable effect in MOSFET response was observed in the temperature range of 23-40 degrees C. The energy dependence of a MOSFET dosimeter was within +/-3.0% for 6-18MeV electron beams and 5.5% for 4MeV ones. This study shows that MOSFET detectors are suitable for dosimetry of electron beams in the energy range of 4-18MeV.

Application of lot sampling of sputum AFB smears for the assessment of microscopy centres

SETTING

Designated microscopy centres (DMC) and additional microscopy centres (AMC) performing sputum acid-fast bacilli (AFB) microscopy, the District TB Centre (DTC) and a reference laboratory (RL).

OBJECTIVES

To ascertain the feasibility of adopting lot sampling of AFB smears and to assess the performance of MCs employing Senior Tuberculosis Laboratory Supervisors (STLS) with no knowledge about the principles of quality assurance of AFB microscopy and RL-based laboratory technicians with training on quality assurance for blinded checking of AFB smears.

METHODS

Slides from MCs were transported to the DTC and the RL; 20 smears per month per MC were selected systematically; 1547 slides from DMCs and 726 from AMCs were checked, respectively, by STLSs at the DTC and by RL laboratory technicians. Discrepancies were resolved by referee.

RESULTS

The discrepancy between MC laboratory technicians and STLSs at the DTC was 4.7%, compared to 1% at the RL. The STLSs and RL-based laboratory technicians had 70 and 2 errors, respectively.

CONCLUSIONS

Lot sampling of AFB smears is feasible under field conditions. Assessment of MCs was more valid with RL-based technicians trained in principles of quality assurance of sputum AFB microscopy than with STLSs with no such training and working in the field.

Phase II trial of Oxaliplatin and 5-Fluorouracil/Leucovorin combination in epithelial ovarian carcinoma relapsing within 2 years of platinum-based therapy

OBJECTIVE

To evaluate the efficacy and toxicity of Oxaliplatin and 5-Fluorouracil (5-FU)/Leucovorin (LV) combination in ovarian cancer relapsing within 2 years of prior platinum-based chemotherapy in a phase II trial.

METHODS

Eligible patients had at least one prior platinum-based chemotherapy regimen, elevated CA-125 > or = 60 IU/l, radiological evidence of disease progression and adequate hepatic, renal and bone marrow function. Patients with raised CA-125 levels alone as marker of disease relapse were not eligible. Oxaliplatin (85 mg/m(2)) was given on day 1, and 5-Fluorouracil (370 mg/m(2)) and Leucovorin (30 mg) was given on days 1 and 8 of a 14-day cycle.

RESULTS

Twenty-seven patients were enrolled. The median age was 57 years (range 42-74 years). The median platinum-free interval (PFI) was 5 months (range 0-17 months) with only 30% of patients being platinum sensitive (PFI > 6 months). Six patients (22%) had two prior regimens of chemotherapy. A total of 191 cycles were administered (median 7; range 2-12). All patients were evaluable for toxicity. The following grade 3/4 toxicities were noted: anemia 4%; neutropenia 15%; thrombocytopenia 11%; neurotoxicity 8%; lethargy 4%; diarrhea 4%; hypokalemia 11%; hypomagnesemia 11%. Among 27 enrolled patients, 20 patients were evaluable for response by WHO criteria and 25 patients were evaluable by Rustin's CA-125 criteria. The overall response rate (RR) by WHO criteria was 30% (95% CI: 15- 52) [three complete responses (CRs) and three partial responses (PRs)]. The CA-125 response rate was 56% (95% CI: 37-73). Significantly, a 25% (95% CI: 9-53) radiological and a 50% (95% CI: 28-72) CA-125 response rate were noted in platinum resistant patients (PFI < 6 months). The median response duration was 4 months (range 3-12) and the median overall survival was 10 months.

CONCLUSION

Oxaliplatin and 5-Fluorouracil/Leucovorin combination has a good safety profile and is active in platinum-pretreated advanced epithelial ovarian cancer.

The Leicester radiotherapy bite block: an aid to head and neck radiotherapy

We describe the construction of a custom-made bite block to be used during external beam radiotherapy to the oral cavity. The bite block is made with standard maxillofacial prosthetic techniques and materials. The design allows accurate and reproducible positioning of the perioral tissues to aid planning of radiotherapy and treatment. The compressibility of this device improves comfort for the patient, while it is in use.

Relative clinical influence of tumor dose versus dose per fraction on the occurrence of late normal tissue morbidity following larynx radiotherapy

A study was made of 242 cases of T2 No glottic cancer treated by definitive radiotherapy over a 15-year period. The aim was to examine the relative influences of tumor biological dose (indicated by locoregional control) versus dose per fraction on the occurrence of late normal tissue effects; in addition, the impact of cord mobility on outcome was analyzed. The 5-year survival corrected for intercurrent deaths was 84% and local disease-free (larynx and/or nodes) survival was 76%. Using Cox regression analysis the only factor significant for local control was cord mobility (p < 0.0001) which also had an effect on overall survival (p < 0.0001); subdivision of T2 glottic staging should be reintroduced into staging classifications. It is evident that comparison of clinical results between centers is potentially prejudiced by an array of factors relating not only to fractionation differences but also variation in clinical and organizational aspects of care. Nevertheless, using other published data for comparison, it seems likely that the serious morbidity rate of 4.1% seen in this study is due in some part to the high tumor biological dose (resulting in high local control). The influence of fraction size was difficult to discern as equivalence in local control was not seen in the data chosen.

Neuroendocrine carcinomas of the larynx

The clinical and histopathological characteristics of seven cases of Moderately Differentiated Neuroendocrine Carcinomas (MDNEC) and two cases of Poorly Differentiated Neuroendocrine Carcinomas (PDNEC) have been reviewed. The tumours arose in the supraglottis of predominantly elderly men. Two cases had raised levels of urinary 5-hydroxy-indole-acetic acid at presentation but no case developed the carcinoid syndrome. PDNEC were histologically identical to the oat cell type carcinoma of the bronchus and were associated with an extremely aggressive clinical course with both patients dying of widespread metastases within one month of registration. MDNEC also metastasized frequently with four of seven cases dying with widespread disease. The tumours have previously been reported as not being radiosensitive; however three cases remain free of disease following biopsy and radiotherapy alone. The place of radiotherapy in the management of these tumours is discussed.