Definitive Radiotherapy With Low Cumulative Doses For Uterine Cervical Cancer : a Japanese Prospective Study With No Midline Block

Background: Several studies have shown favourable treatment outcomes for Japanese patients with cervical cancer treated with definitive radiotherapy (RT) at low cumulative doses. However, a midline block (MB) used in whole pelvic RT (WPRT) hinders accurate interpretation of the treatment outcome due to uncertainty of the RT dose delivered to cervical tumours. Methods: Patients with cervical cancer of FIGO stages IB1u2013IVA were eligible for this prospective study. The treatment protocol consisted of WPRT (non-IMRT) without a MB (45 Gy/25 fractions) and high-dose-rate intracavitary brachytherapy (HDR-ICBT; 15 Gy/3 fractions or 20 Gy/4 fractions, prescribed to point A). The total EQD2 to point A was 63 or 69.3 Gy. CT-based planning was performed for HDR-ICBT. Organs at risk were contoured for each ICBT application. The HR-CTV was contoured at the time of the present analyses. If optimisation (manual adjustment of the dwell times) was inadequate to meet the organ-at-risk dose constraints, the point A dose was decreased. Graphical optimisation was not allowed. Results: A total of 40 patients were enrolled in the study. The FIGO stage distribution was IB1 in 11 patients, IB2 in 13, IIA2 in 1, IIB in 11, IIIB in 3 and IVA in 1 patient. The median pretreatment tumour diameter was 47 mm (14u201381 mm). No patients received hybrid ICBT. The point A dose was decreased in 19 of 153 ICBT sessions (12%). After a median follow-up of 33 months, the 2-year pelvic progression-free survival, disease-free survival and overall survival rates were 83%, 75% and 85%, respectively. A HR-CTV D90 threshold of 70 Gy was correlated with the pelvic progression-free survival rate: 93% for patients receiving u2265 70 Gy (n=29) versus 64% for those receiving < 70 Gy (n=11) (P=0.018). Late adverse events (grade u2265 3) were observed in three patients (bladder in two, rectum in one). Conclusions: Definitive RT consisting of WPRT without a MB and HDR-ICBT was feasible in our cohort of Japanese patients. A low RT dose might be adequate for patients with non-bulky tumours. Proper 3D-IGBT using graphical optimisation and a suitable hybrid technique, based on appropriate HR-CTV contouring, is recommended to improve outcomes further.