title: Correlation of point B and lymph node dose in 3D-planned high-dose-rate cervical cancer brachytherapy.
abstract: OBJECTIVE
  To compare high dose rate (HDR) point B to pelvic lymph node dose using three-dimensional-planned brachytherapy for cervical cancer.
  
  
  METHODS
  Patients with FIGO Stage IB-IIIB cervical cancer received 70 tandem HDR applications using CT-based treatment planning. The obturator, external, and internal iliac lymph nodes (LN) were contoured. Per fraction (PF) and combined fraction (CF) right (R), left (L), and bilateral (Bil) nodal doses were analyzed. Point B dose was compared with LN dose-volume histogram (DVH) parameters by paired t test and Pearson correlation coefficients.
  
  
  RESULTS
  Mean PF and CF doses to point B were R 1.40 Gy +/- 0.14 (CF: 7 Gy), L 1.43 +/- 0.15 (CF: 7.15 Gy), and Bil 1.41 +/- 0.15 (CF: 7.05 Gy). The correlation coefficients between point B and the D100, D90, D50, D2cc, D1cc, and D0.1cc LN were all less than 0.7. Only the D2cc to the obturator and the D0.1cc to the external iliac nodes were not significantly different from the point B dose. Significant differences between R and L nodal DVHs were seen, likely related to tandem deviation from irregular tumor anatomy.
  
  
  CONCLUSIONS
  With HDR brachytherapy for cervical cancer, per fraction nodal dose approximates a dose equivalent to teletherapy. Point B is a poor surrogate for dose to specific nodal groups. Three-dimensional defined nodal contours during brachytherapy provide a more accurate reflection of delivered dose and should be part of comprehensive planning of the total dose to the pelvic nodes, particularly when there is evidence of pathologic involvement.
authors.affiliation: Harvard Radiation Oncology Program, Department of Radiation Oncology, Brigham and Women's Hospital/Dana-Farber Cancer Institute, 75 Francis Street, Boston, MA 02115, USA.
authors.forename: Larissa J
authors.initials: LJ
authors.lastname: Lee
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Sadow
authors.forename: Anthony
authors.initials: A
authors.lastname: Russell
authors.forename: Akila N
authors.initials: AN
authors.lastname: Viswanathan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000473:pathology; D015182:Lymphatic Irradiation / Q000379:methods*; D008875:Middle Aged; D010388:Pelvis; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D047368:Tumor Burden; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*