Ground Glass vs. Radiation Pneumonitis/Fibrosis? - 1273361

Hello,
My dad was diagnosed with Stage IV NSCLC in Oct 2015. Mutational composition is EGFR Exon 20, MET amplification and p53 gene loss. Our first line of treatment was 10x radiation to bone mets: 7th and 9th left ribs and 2 vertebrae followed by 4 rounds of carboplatin/pemetrexed. He is also on Lovenox for a PE spotted in his left lower lobe.

We just had a CT Scan after the 4 cycles of chemo and all tumors either remained stable or shrank except for an area of ground glass in the left lower lobe, which became larger. Our oncologist believes this is an area of cancer with a likely different mutation, which is why it is not responding to the chemo the same way the other tumor sites (mets in lymph nodes, spine, ribs) are.

The ground glass in the LLL was always mentioned in various ways on past scans. First as a 1.2 cm nodular opacity with "patchy consolidation" on our initial CT scan in October 2015. On our Nov 2015 PET it showed up as 2.5 x 1.5cm with a SUV of 3.1. The radiologist noted re: this area: "relatively low level of subtle increased uptake, likely inflammatory, PE cannot be excluded." We had a baseline CT done before starting chemo in December 2015 and ground glass in lower left lobe was mentioned but without measurement. On our post-chemo scan last week, the same area was now described as 4.3 x 6.5 cm ground glass with 15 x 8mm nodule, but the radiologist noted, "Development of ground glass adjacent to treated rib lesion consistent with radiation pneumonitits/radiation fibrosis."

Our current plan is to continue with 3 rounds of Alimta maintenance but figuring out a back up plan (perhaps an immunotherapy trial) in the meantime due to this ground glass situation. The big question is: how can you tell the difference between pneumonitis/radiation fibrosis and progression?

Any insights about this will be much appreciated!
Pavla