Purpose: To review dosimetry and associated toxicity in patients treated with CT-guided IVRT in an effort of predicting prior radiation dose volume constraints in patients who have received non-CT guided IVRT, and present with recurrence requiring re-irradiation.
Methods: 29 patients with endometrial cancer treated at our institution with upfront surgery +/- RT +/- chemo subsequently presented with an isolated vaginal recurrence and were salvaged with brachytherapy +/- EBRT. All patients received CT-guided IVRT (prescriptions ranging from 4 x 5 – 5 x 5 (Gy x fx)) and 18/29 received EBRT (prescription 1.8 Gy x 25fx) . Bowel, rectum, bladder, and rectosigmoid) were contoured at the time of the IVRT . D2cc was retrospectively analyzed for each OAR as physical dose (Gy) from the IVRT course only, using DVHs. Toxicity was collected for each patient prospectively at routine clinical follow-up and graded according to Common Terminology Criteria for Adverse Events v5.0.
Results: The median (range) D2cc for bowel was 1.86 (4.2 – 0.94 Gy), for rectosigmoid was 2.1 (4.75 – 0.4 Gy), for bladder was 3.4 (5.3 – 2.0 Gy), and for rectum was 3.4 (5.0 – 1.7 Gy). One patient treated with EBRT and IVRT experienced a grade 3 sacral insufficiency fracture (3.4%). Grade 1 and 2 toxicity was recorded in 14 (48.3 %) and 13 (44.8%) patients respectively. D2cc for bladder, rectum, bowel and rectosigmoid was less than prescription dose in 90%, 86%, 100%, and 100% of the patients respectively.
Conclusion: Overall salvage IVRT was well tolerated. 14% of patients received OAR D2cc greater than prescription with only 2 with grade 2 toxicities. These preliminary results suggest that using D2cc equal to the prescription dose is clinically acceptable for all OAR as a prior radiation dose volume constraint in patients who have received non-CT IVRT, and requiring re-irradiation.
Not Applicable / None Entered.