Is there a firm rib dose constraint when treating lung tumors abutting the visceral pleura/chest wall with SBRT?

While I am concerned about chestwall pain and rib fractures, I am usually reluctant to alter my volume or dose. At the Radium Society Meeting in 2013, Ben Slotman released data on local recurrences after SBRT, and he found a 3 year recurrence rate of ~8%. More interestingly, he found that 56% of the recurrences were in tumors that were immediately adjacent to the chestwall. He postulated this may be due to dose/volume changes over a concern for chestwall toxicity.

I agree with Thomas. When Brian Kavanagh, Tracey Schefter and I originally published the dose volume constraint for chest wall, we found that 30cc receiving 30Gy was most correlative with chest wall toxicity. I think what people commonly do is use this as a hard constraint and compromise coverage. Residents especially need to remember that these constraints represent probabilities for toxicity but are not absolute. I tell my residents that although chest wall toxicity can be severe, the tumor st...