The impact of a vaginal brachytherapy boost to pelvic radiation in stage III endometrial cancer.

PURPOSE: We investigate the use and impact of a vaginal brachytherapy boost (VBB) after pelvic radiotherapy for stage III endometrial adenocarcinoma on vaginal and pelvic control. MATERIAL AND METHODS: One hundred patients treated from 1998-2011 with surgery and adjuvant therapy with or without a VBB were included. Variables examined were grade, stage, lymphovascular space invasion (LVSI), vaginal involvement (VI), cervical stromal involvement (CSI), myometrial invasion (MI), and a VBB. Failure was scored as vaginal, or pelvic. Fisher's exact test assessed association between variables with vaginal and pelvic control. RESULTS: With a median follow up of 43 months, 31% were stage IIIA, 6% stage IIIB, and 63% stage IIIC. Thirty-eight (38%) received pelvic radiotherapy alone, and 62% received adjuvant chemotherapy. Of the 100 patients, 82 were treated with a VBB, 10 were not treated with a VBB, and 8 were not treated with RT. Of the 82 patients who received a VBB, 5 failed in the vagina with vaginal and pelvic control rates of 94% and 92%. The impact of VB reached borderline significance with its impact on pelvic control, 92% vs. 70% (p = 0.056), and did not affect vaginal control, 94% and 90% (p = 0.50). Neither tumor grade, LVSI, CSI, stage, nor LVSI (p > 0.05) statistically significantly impacted vaginal control. CONCLUSIONS: There are no clinical guidelines for the use of a VBB in stage III endometrial cancer. The majority of our patients were treated with a VBB and experienced excellent pelvic and vaginal control. The presence of traditional adverse features did not negatively impact control in our patient cohort. However, the role of a VBB needs further investigation to understand the incremental benefit beyond pelvic RT.

Dose delivered to the lumbosacral plexus from high-dose-rate brachytherapy for cervical cancer.

OBJECTIVE: To calculate dose delivered to the lumbosacral plexus (LSP) with cervical brachytherapy using 3-dimensional imaging, and to compare this with the position of the tandem in the pelvis using bony landmarks. We also report long-term LSP toxicity outcomes. METHODS AND MATERIALS: Treatment planning images from 55 patients treated with tandem and ring brachytherapy from October 2009 through November 2012 were reviewed. The LSP was contoured on planning computed tomographic scans to calculate dose received. Lumbosacral plexus dose was studied as a function of tandem distance from the sacrum and pubic symphysis (STratio) measured on digitally reconstructed radiographs. Patient and implant characteristics were included as covariates on LSP dose. Clinical follow up on LSP toxicity was recorded. RESULTS: Patients were prescribed 550 to 700 cGy using computed tomography-based imaged-guided brachytherapy for 4 to 5 fractions. The maximum dose to 2 cc (D2cc) of LSP ranged from 44 to 287 cGy per implant. The median D2cc was 118 cGy, corresponding to 18% of prescription dose. Patients with an STratio less than 0.33 (closer to the sacrum) and at least 0.33 had median LSP doses of 138 and 98 cGy, respectively. Lumbosacral plexus dose did not change significantly with body mass index, uterus position, or tumor stage. Two patients reported symptoms of peripheral neuropathy, with a median follow-up of 14.7 months. CONCLUSIONS: The mean D2cc per fraction to the LSP is roughly 20% of the prescribed high dose-rate and varies with the position of the tandem from the sacrum. The dose threshold for radiation-induced neuropathy of the LSP remains undefined.

A comparison of soft-tissue implanted markers and bony anatomy alignments for image-guided treatments of head-and-neck cancers.

PURPOSE: To compare the geometric alignments of soft-tissue implanted markers to the traditional bony-based alignments in head-and-neck cancers, on the basis of daily image guidance. Dosimetric impact of the two alignment techniques on target coverage is presented. METHODS AND MATERIALS: A total of 330 retrospective alignments (5 patients) were performed on daily megavoltage computed tomography (MVCT) image sets using both alignment techniques. Intermarker distances were tracked for all fractions to assess marker interfractional stability. Using a deformable image registration algorithm, target cumulative doses were calculated according to generated shifts on daily MVCT image sets. Target D95 was used as a dosimetric endpoint to evaluate each alignment technique. RESULTS: Intermarker distances overall were stable, with a standard deviation of <1.5 mm for all fractions and no observed temporal trends. Differences in shift magnitudes between both alignment techniques were found to be statistically significant, with a maximum observed difference of 8 mm in a given direction. Evaluation of technique-specific dose coverage based on D95 of target clinical target volume and planning target volume shows small differences (within +/-5%) compared with the kilovoltage CT plan. CONCLUSION: The use of daily MVCT imaging demonstrates that implanted markers in oral tongue and soft-palate cancers are stable localization surrogates. Alignments based on implanted markers generate shifts comparable overall to the traditional bony-based alignment, with no observed systematic difference in magnitude or direction. The cumulative dosimetric impact on target clinical target volume and planning target volume coverage was found to be similar, despite large observed differences in daily alignment shifts between the two techniques.