We investigated if an adaptive radiotherapy approach based on cone beam CT (CBCT) acquired during radical treatment was feasible and resulted in improved dosimetric outcomes for bladder cancer patients compared to conventional planning and treatment protocol. A secondary aim was to compare a conventional plan with a theoretical online process where positioning is based on soft tissue position on a daily basis and treatment plan choice is based on bladder size. A conventional treatment plan was derived from a planning CT scan in the radical radiotherapy of five patients with muscle invasive bladder cancer. In this offline adaptive protocol using CBCT, the patients had 10 CBCT: daily CBCT for the first five fractions and then CBCT scan on a weekly basis. The first five daily CBCT in each patient were used to create a single adaptive plan for treatment from fraction eight onwards. A different process using the planning CT and the first five daily CBCT was used to create small, average and large bladder volumes, giving rise to small, average and large adaptive bladder treatment plans, respectively. In a retrospective analysis using the CBCT scans, we compared the clinical target volume (CTV) coverage using three protocols: (i) conventional; (ii) offline adaptive; and (iii) online adaptive with choice of 'plan of the day'. Daily CBCT prolonged treatment time by an average of 7 min. Two of the five patients demonstrated such variation in CTV that an offline adaptive plan was used for treatment after the first five CBCT. Comparing the offline adaptive plan with the conventional plan, the CTV coverage improved from a minimum of 60.1 to 94.7% in subsequent weekly CBCT. Using the CBCT data, modelling an online adaptive protocol showed that coverage of the CTV by the 95% prescribed dose line by small, medium and large adaptive plans were 34.9, 67.4 and 90.7% of occasions, respectively. More normal tissue was irradiated using a conventional CTV to planning target volume margin (1.5 cm) compared to an online adaptive process (0.5 cm). An offline adaptive strategy improves dose coverage in certain patients to the CTV and results in a higher conformity index compared to conventional planning. Further research in online adaptive radiation therapy for bladder cancer is indicated.
BackgroundImage-guided radiotherapy (IGRT) increases the accuracy of treatment delivery through daily target localisation. We report on toxicity symptoms experienced during radiotherapy treatment, with and without IGRT in prostate cancer patients treated radically.MethodsBetween 2006 and 2009, acute toxicity data for ten symptoms were collected prospectively onto standardized assessment forms. Toxicity was scored during radiotherapy, according to the Common Terminology Criteria Adverse Events V3.0, for 275 prostate cancer patients before and after the implementation of a fiducial marker IGRT program and dose escalation from 74Gy in 37 fractions, to 78Gy in 39 fractions. Margins and planning constraints were maintained the same during the study period. The symptoms scored were urinary frequency, cystitis, bladder spasm, urinary incontinence, urinary retention, diarrhoea, haemorrhoids, proctitis, anal skin discomfort and fatigue. Analysis was conducted for the maximum grade of toxicity and the median number of days from the onset of that toxicity to the end of treatment.ResultsIn the IGRT group, 14228 toxicity scores were analysed from 249 patients. In the non-IGRT group, 1893 toxicity scores were analysed from 26 patients. Urinary frequency ≥G3 affected 23% and 7% in the non-IGRT and IGRT group respectively (p = 0.0188). Diarrhoea ≥G2 affected 15% and 3% of patients in the non-IGRT and IGRT groups (p = 0.0174). Fatigue ≥G2 affected 23% and 8% of patients in the non-IGRT and IGRT groups (p = 0.0271). The median number of days with a toxicity was higher for ≥G2 (p = 0.0179) and ≥G3 frequency (p = 0.0027), ≥G2 diarrhoea (p = 0.0033) and ≥G2 fatigue (p = 0.0088) in the non-IGRT group compared to the IGRT group. Other toxicities were not of significant statistical difference.ConclusionsIn this study, prostate cancer patients treated radically with IGRT had less severe urinary frequency, diarrhoea and fatigue during treatment compared to patients treated with non-IGRT. Onset of these symptoms was earlier in the non-IGRT group. IGRT results in less acute toxicity during radiotherapy in prostate cancer.
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