Chest Wall Volume Receiving >30 Gy Predicts Risk of Severe Pain and/or Rib Fracture After Lung Stereotactic Body Radiotherapy

Exploratory analysis using machine learning to predict for chest wall pain in patients with stage I non‐small‐cell lung cancer treated with stereotactic body radiation therapy

“…However, this does not imply that rib and chest wall doses can be simply disregarded since (a) CWS can result without the clinical appearance of rib fractures and (b) increasing risk may still occur with increasing dose in a continuous fashion 18. Other prior studies have examined factors including rib Dmax, rib dose to 0.5 cc, 2 cc, rib V30, V40, chest wall Dmax, chest wall dose to 8 cc, and chest wall V30, without clear indication of the relative superiority or inferiority of one of these dosimetric factors relative to the others 9, 13, 27, 29, 38, 39. Global Dmax and fraction size are also suggested to be important indicators of toxicity, with higher rates of radiation‐induced rib fracture of ~50% for DMax > 54 Gy and fraction size >8 Gy 16.…”

“…All patients were planned with a constraint goal to keep 30 cc of the chest wall to <30.0 Gy. Twenty‐five parameters (termed features in the machine learning analysis) suspected of a correlation or previously reported10, 12, 13, 15, 17, 27, 28, 29, 30, 31 to associate with CWS were analyzed, including patient and tumor characteristics and dosimetric features were recorded for each patient. Toxicities were assessed using CTCAEv4 criteria for chest wall pain, where Grade 1 represents mild pain, Grade 2 represents moderate pain limiting instrumental activities of daily living (ADL), and Grade 3 represents severe pain limiting self‐care ADL.…”

“…Radiation‐related chest wall toxicity can result from radiation‐induced rib fracture or chest wall syndrome (CWS). In the absence of rib fracture, CWS is caused by radiation‐induced neuropathy of the intercostal nerves or nerve branches, chest wall edema, chest wall fibrosis, or hairline rib fractures not clearly visible on imaging 12, 13, 14…”

A hybrid planning strategy for stereotactic body radiation therapy of early stage non‐small‐cell lung cancer

“…The maximum point dose and dose‐volume constraints of several critical structures are listed in Table 1 for both 54 Gy and 50 Gy protocols 11, 12, 13. Selected dose‐volume parameters were compared, including the conformity index ( CI 50 , ratio of the volume receiving 50% of prescription dose to the PTV volume), V 20 and V 5 (lung volumes receiving 20 Gy and higher, and 5 Gy and higher, respectively) for combined lungs, V 30 Gy (volume receiving 30 Gy and higher) for the chest wall, and D 0.035 cc (dose to 0.035 cc of the volume, a representative of maximum dose) for all other critical structures such as the spinal cord, aorta, trachea, etc.…”

Practical methods for improving dose distributions in Monte Carlo‐based IMRT planning of lung wall‐seated tumors treated with SBRT

“…This metric was chosen as the nearby OARs to the LW‐seated tumor are especially sensitive to the maximum dose (or dose to a small volume) in the treatment plan. For example, the ribs are a common nearby OAR and do not demonstrate a volume effect, but rather a threshold dose effect; if too high a dose is applied, then pain and fracture can result 26 , 27 . It is also important to have a metric to assess the low‐dose spillage, as this could change depending on the method used.…”