Pelvic Bone Marrow

Much of an adult's active bone marrow lies in the pelvis — the iliac crests, sacrum, acetabula and upper femurs.

Bone marrow makes the body's blood cells; in adults, much of the active marrow lies in the pelvic bones.

Pelvic IMRT with concurrent chemotherapy (5-FU and mitomycin-C in anal cancer, capecitabine in rectal cancer) can suppress blood counts. The wide elective nodal volumes of anal cancer pass close to the iliac bones, so anal cancer protocols add volume limits for the pelvic bones to reduce hematologic toxicity.

In gynecologic treatment the pelvic nodal volumes also run along the iliac bones, and weekly cisplatin is common with definitive cervix treatment, so NRG's cervix, endometrial and vulva templates all include bone marrow goals — a mean dose and the volume above 10 and 20 Gy or 10 and 40 Gy.

The NRG anal cancer template contours BoneMarrow from the outer bone contours of the sacrum, iliac crests, acetabula and proximal femurs as one solid, continuous structure, stopping at the bottom at the level of the ischial tuberosities.

Definitions vary between protocols, and a limit applies only to the structure it was written for, so match your contour to your protocol.