e558 Background: Salvage options for those with local recurrence after XRT include surgery, brachytherapy, cryotherapy or high-frequency ultrasound. However, the risk of significant complications (e.g. fistula, incontinence, bladder neck contracture), is not insignificant. The sensitivity of multiparametric MRI in detecting viable cancer within the prostate is now more than 70%. The objectives of this pilot study are to explore the toxicities, QOL and efficacy of focal salvage HDR brachytherapy in patients with MRI-visible biopsy-confirmed local recurrence. Methods: Eligible patients included: multiparametric 3T MRI-visible biopsy-confirmed local recurrence > 30 months after XRT, negative metastatic workup, IPSS < 15, post-XRT PSA < 10ng/mL, prostate volume ≤ 50cc. The ultrasound-based HDR brachytherapy prescription dose was 27Gy divided over two implants separated by 1 week to the target volume (TV) with dose constraints to the urethra and rectum. Follow-up PSA, IPSS, EPIC QOL and CTCAE v4.0 toxicities were collected. Results: 15 patients (mean age 73 years) were enrolled in the study. Median follow up was 30 months (12-42). At initial presentation, there were 5, 8 and 2 low-, intermediate- and high-risk disease, and initial XRT dose was 70-78Gy. The Gleason score of the local recurrence was 6, 7 and 8-10 in 1, 7 and 6, respectively, and not classified in 1 patient. The pre-HDR median PSA was 4.13 (1.30 – 9.29). The median size of the recurrence on MRI was 9mm (7-20), TV 6.1cc (2.2-16.1), TV V100 96.3%, TV D90 110.9%, urethral D10 64.5% and rectal D10 36.0%. No acute/late GU/GI grade 3-5 toxicities, nor urinary retention, were observed. The most common acute toxicity was frequency and nocturia. Median IPSS at baseline, 1-, 3-, 6-, 12-, 18-, 24-months was 4, 8, 5, 5, 8 and 5 (p = 0.72). Three year PSA failure free rate was 71%. There was no significant change in EPIC domains. Conclusions: Early toxicity, QOL and PSA failure-freedata suggests that focal salvage HDR brachytherapy is well tolerated and effective. Clinical trial information: NCT01583920.
To evaluate and compare the biological impact on different proposed margin recipes for the same geometric uncertainties for intra-hepatic tumors with different tumor cell types or clinical stages. Three different margin recipes based on tumor motion were applied to sixteen IMRT plans with a total of twenty two intra-hepatic tumors. One recipe used the full amplitude of motion measured from patients to generate margins. A second used 70% of the full amplitude of motion, while the third had no margin for motion. The biological effects of geometric uncertainty in these three situations were evaluated with Equivalent Uniform Doses (EUD) for various survival fractions at 2 Gy (SF2). There was no significant difference in the biological impact between the full motion margin and the 70% motion margin. Also, there was no significant difference between different tumor cell types. When the margin for motion was eliminated, the difference of the biological impact was significant among different cell types due to geometric uncertainties. Elimination of the motion margin requires dose escalation to compensate for the biological dose reduction due to the geometric misses during treatment. Both patient-based margins of full motion and of 70% motion are sufficient to prevent serious dosimetric error. Clinical implementation of margin reduction should consider the tumor sensitivity to radiation.
Abstract Background and purpose To investigate whether inadequate dose to Point-A necessitates treatment plan changes in a time of computed tomography (CT)-image-guided brachytherapy treatment planning for cervix cancer. Materials and methods A total of 125 tandem and ovoid insertions from 25 cervix patients treated were reviewed. CT-image-based treatment planning was carried out for each insertion. Point-A is identified and the dose documented; however, dose optimisation in each plan was based on covering target while limiting critical organ doses (Plan Target ). No attempts were made to equate prescription and Point-A dose. For each insertion, a second hypothetical treatment plan was generated by prescribing dose to Point-A (Plan Point-A ). Plans were inter-compared using dose–volume histogram analyses. Results A total of 250 treatment plans were analysed. For the study population, the median cumulative dose at Point-A was 80 Gy (range 70–95) for Plan Target compared with 84·25 Gy for Plan Point-A . Bladder and rectal doses were higher for Plan Point-A compared with Plan Target ( p < 0·0001). Target D 90 did not correlate with Point-A dose ( p = 0·60). Conclusions Depending on applicator geometry, tumour size and patient anatomy, Point-A dose may vary in magnitude compared with prescription dose. Treatment plan modifications purely based on inadequate Point-A dose are unnecessary, as these may result in higher organ-at-risk doses and not necessarily improve target coverage.
