Accelerated hypofractionated radiotherapy with 3 Gy per fraction for central/ultra-central lung tumors: toxicity to mediastinal organs.

BACKGROUND: Accelerated hypofractionated radiotherapy with 3 Gy per fraction is routinely performed for central lung tumors in Japan. However, the tolerable doses to mediastinal organs at risk during this procedure are unclear. This study aimed to clarify the rate of toxicities and tolerable doses to mediastinal organs. METHODS: Patients treated with accelerated hypofractionated radiotherapy using a total dose of 60-75 Gy, with 3 Gy per fraction, for central lung tumors (July 2009-April 2021) were retrospectively reviewed. We extracted patients who received ≥30 Gy irradiation to each mediastinal organ and analyzed dosimetric factors, including doses to 0.03, 0.5, 1, 4 and 10 mL of each organ, in relation to grade 3-5 toxicities, except for radiation pneumonitis. RESULTS: In total, 251 organs in 91 (ultra-central, 24) lesions were analyzed, with a median follow-up duration of 26 months (range, 4-94). The prescribed doses were 75/72/69/66/63/60 Gy for 52/14/16/3/2/4 lesions, respectively. Grade 3 bronchopulmonary hemorrhage was confirmed in two (2.2%) patients, whose tumors were located ultra-centrally. The two patients with toxicity received up to 74.5 and 71.6 Gy to the bronchus. Among patients who received 70 Gy or more to the bronchus, the incidence rate was 7% (2/28 patients). CONCLUSION: The rate of severe toxicities was low (2.2%). Although we did not identify the dose tolerance of the organs, because of the low incidence rate, we did note that doses of >70 Gy to the bronchus were likely to cause bronchopulmonary hemorrhage.

Re-irradiation with interstitial brachytherapy in uterine cancer patients with vaginal recurrence after post-operative pelvic irradiation.

PURPOSE: This study aimed to evaluate the outcomes and dose-volume parameters of re-irradiation with interstitial brachytherapy (ISBT) in uterine cancer patients with vaginal recurrence after post-operative pelvic irradiation. MATERIAL AND METHODS: We evaluated six uterine cancer patients who received re-irradiation with ISBT between January, 2012 and December, 2016. As an initial treatment, all patients received post-operative whole pelvic irradiation of 45-50.4 Gy in 25-28 fractions. For vaginal recurrence, all patients were treated with ISBT alone at a dose of 38-42 Gy in 6-7 fractions for clinical target volumes (CTVs) for 3-4 days. RESULTS: Post-operative pelvic irradiation was delivered to five and one patients, using a three-dimensional conformal technique and intensity-modulated radiotherapy, respectively. Median duration from surgery to vaginal recurrence was 25.7 months. Median tumor size just before ISBT was 3.3 cm. Median time from completion of pelvic irradiation to ISBT initiation was 24.1 months. Mean doses per fraction of ISBT for CTV D90 (the minimum dose received by 90% of CTV) and minimum dose received by 2cc (D2cc) for the bladder and for rectum were 6.1 Gy, 4.4 Gy, and 3.8 Gy, respectively. Mean total equivalent dose in 2 Gy fractions (EQD2), including external beam radiotherapy and ISBT, for D2cc for the bladder, sigmoid, and rectum were 92.1 Gy, 50.4 Gy, and 81.6 Gy, respectively. Median follow-up duration was 53.3 months. Local recurrence was observed in two patients, and four of the six patients were alive. Grade 2 late rectal complications occurred in two patients, and no late grade ≥ 3 complications were observed in four alive patients. CONCLUSIONS: Re-irradiation with ISBT may be an effective treatment strategy for gynecological cancer patients with vaginal recurrence after post-operative pelvic irradiation.