Identifies the volume or anatomic target of the most clinically significant regional radiation therapy delivered to the patient during the first course of therapy. See also Rad--Regional RX Modality [1570].

00	No radiation therapy, not applicable
01	Eye/orbit
02	Pituitary
03	Brain (NOS)
04	Brain (limited)
05	Head and neck (NOS)
06	Head and neck (limited)
07	Glottis
08	Sinuses
09	Parotid
10	Chest/lung (NOS)
11	Lung (limited)
12	Esophagus
13	Stomach
14	Liver
15	Pancreas
16	Kidney
17	Abdomen (NOS)
18	Breast
19	Breast/lymph nodes
20	Chest wall
21	Chest wall/lymph nodes
22	Mantle, mini-mantle
23	Lower extended field
24	Spine
25	Skull
26	Ribs
27	Hip
28	Pelvic bones
29	Pelvis (NOS)
30	Skin
31	Soft tissue
32	Hemibody
33	Whole body
34	Bladder and pelvis
35	Prostate and pelvis
36	Uterus and Cervix
37	Shoulder
38	Extremities bone, NOS
39	Inverted Y
40	Spinal cord
41	Prostate
50	Thyroid
60	Lymph node region, NOS
98	Other
99	Unknown