Modeling correlation indices between bladder and Foley's catheter balloon dose with CT-based planning using limited CT slices in intracavitary brachytherapy for carcinoma of cervix.

PURPOSE: To derive and validate an index to correlate the bladder dose with the catheter balloon dose using limited computed tomography (CT) slices. MATERIALS AND METHODS: Applicator geometry reconstructed from orthogonal radiographs were back-projected on CT images of the same patients for anatomy-based dosimetric evaluation. The correlation indices derived using power function of the catheter balloon dose and the bladder volume dose were validated in 31 patients with cervical cancer. RESULTS: There was significant correlation between International Commission on Radiation Units (ICRU)-38 balloon reference dose (Dr) and the dose received by 25% bladder volume (D(25)) (P< 0.0001). Significant correlation was also found between the reference dose of mid-balloon point (D(rm)) and the dose to D(25) (P < 0.0001). Average percentage difference [100 x (observed index - expected index)/ expected index] of observed value of I'25 (index for the dose to D25 bladder with respect to mid-balloon reference point) from that of expected value was 0.52%, when the index was modeled with reference dose alone. Similarly the average percentage difference for I'10cc (index for the dose to 10 cc volume of bladder with respect to mid balloon point) was 0.84%. When this index was modeled with absolute bladder volume and reference dose, standard deviation of the percentage difference between observed and expected index for D(rm) reduced by approximately 2% when compared to D(r). CONCLUSION: For clinical applications, correlation index modeled with reference dose and volume predicts dose to absolute volume of bladder. Correlation index modeled with reference dose gives a good estimate of dose to relative bladder volume. From our study, we found D(rm) to be a better indicator of bladder dose than D(r).

Comparative Evaluation of Concurrent Chemotherapy & Hyperfractionated radiotherapy Versus Conventional Radiotherapy alone in the Treatment of Locally Advanced Carcinoma Cervix-A Prospective Randomised Study

The aim of this study was to determine whether the addition of concurrent cisplalin and hyperfractionation in external pelvic radiotherapy improves local control and survival in patients with locally advanced carcinoma cervix as compared to treatment with conventional radiptjerapy alone. The morbidity of two treatment protocols was also compared. Sixty patients of newly diagnosed squamous cell carcinoma cervix, FIGO stage 118 and III were randomised into the following two treatment protocols: Group A (study group): Cisplatin30 mg/m2 weekly x 5 courses and external beam pelvic radiotherapy 50 Gy/33#4.5 weeks with hyperfractionation in first and following weeks. Group B (control group) : External beam pelvic radiotherapy 46 Gy/23#/4.5 weeks. Patients in both the group were then treated with intracavitary brachytherapy by LDR/MDR Selectron and a dose of 28 Gy was delivered to point A. The patients who were not suitable for intracavitary treatment were treated by supplementary external beam pelvic radiotherapy 20 Gy/ 10#/2" ceks. The actuarial local control at 4 years was 60% in group A and 42% in Group 8 9p<0.05). The a Cluarial disease free survival at 4 years was 52% in Group A and 35% in Group 8 (p<0.05). Only grade I acute and delayed haematological toxicity and grade I nausea and vomiting as acute toxicity "ere significantl) higher for Group A patients as compared to Group 8. Concomitant chemotherapy with hyperfraclionated radiotherapy is well tolerated and seems to offer potential benefit for imprOl ing the locoregional control in locally advanced carcinoma of cervix.