Session Item

To evaluate  pelvic bone marrow (PBM) dose  and correlation with grade 2 or higher hematological toxicity (HT) in patients with cervical cancer treated by  three- dimensional conformal pelvic radiotherapy  (3D-CRT) .

Retrospective study including 20 patients with  local advanced cervical cancer  treated  at Radiation Oncology Departement of Farhat Hached hospital  in Tunisia between 2018  and 2020   . Medical records and data on patient and tumour characteristics, Common Toxicity Criteria (CTC) scores, laboratory tests, and treatment data were retrieved and analyzed. The clinical target volume consisted of the pelvic and presacral lymph nodes , uterus and cervix, upper vagina, and parametrial tissue.The external contour of the (PBM), which comprised the lumbosacral spine and ilium and the ischium, pubis, and proximal femur  was delineated on the planning CT scan  .We reported  volume and DVH parameters (V10, V20, V40 and Dmax) of PBM  and of  ilium separetelly. The hematological parameters during RT were analyzed for higher than grade 2 HT (Radiation Therapy Oncology Group)  and correlated with DVH parameters using log regression analysis (P < 0.05 significant).

The median age of patients was  52 years old(28-70).Clinical symptomatology was dominated by  metrorrhagia in 100% of cases. 80% of patients  had stage IIB disease, one patient had  stage IIIC1 with enlarge nodes on MRI (≥10 mm) (FIGO 2018). All patients underwent 3D-CRT, using four-field box technique consisted of anterior, posterior, right, and left lateral beam directions. Concurrent weekly  cisplatin was administered in 90% cases  for a median of 4 courses(1-5) .The median treatment time was  41days (30-51) . Low dose Brachytherapy (LDR) using 192Iridium implant was delivred to 75% cases . Only 3 patients underwent hysterectomy after overall treatment.

In our experience, acute Grade 3 or greater HT was  35%, although Grade 2 or greater HT has approached  60%. The leukopenia, neutropenia, anemia, and thrombocytopenia higher than grade 2 was noted in 20%, 10%, 55%, and20 %, respectively .The mean DVH parameters V10, V20, and V40 for PBM were  92 %, 86% and 42 %;  the mean Dmax was  49,84 Gy( 64-69). Whole pelvis V40 was  ≥ 37% in 17 cases. The mean DVH parameters V10, V20, and V40 for ilium were 96%, 88%,and 45% .On  univariate analyses,   whole pelvis V40 ≥ 40%  correlated with  HT grade  2 or higher was no significant (p =0.06) .The median follow up was 7months (3-35).No late hematotoxicities was revealed .

Our dosimetric analysis suggests that, in patients undergoing 3D-CRT concurrent chemotherapy for local advanced cervical cancer, bone marrow and cortical bone sructure are all often neglected as organs at risk and receives significantly high doses . Further prospective studies validating significance of high-dose effects and identifying correlation of bioimaging with CT contouring are warranted.