Radiation tx just because of large tumor?

Noticed a very large mass in May 09.  Due to very dense breast tissue, the mass was diffiicult to image on M/G and U/S.  Bx showed IDC, grade 2.  MRI found 3 masses, primary originally said to be 5 cm w/ other 2 (possible satellite lesions) said to be 1.6 cm and 1.0 cm - (assumed multicentric disease but smaller masses had no bx).  Onc ordered neoadjuvant TC chemo x 6.  MRI after first 2 cycles showed significant shrinkage of primary mass (to 3.6 cm) w/ 2 smaller masses no longer seen.  MRI following cycle 4 stated additional shrinkage and reduced enhancement.  MRI after cycle 6 showed no significant change -- "consistent w/ incomplete response"  and stated size as 3.6 cm.  Based on primary tumor originally being 5 cm or larger based on MRI, Rad Onc recomended rad tx following mastectomy, even if sentinel nodes are negative.  Surgeon says b/c I got chemo first that shrank the mass, I am in an area w/ little research -- should the original MRI-measured mass or the actual cancerous part of the mass and nodes r/m at surg be the deciding factor?   B/c I am thin and don't have enough fat for the various FLAP-type reconstruction procedures, implants are my best option but are not optimal following rad tx due to scar tissue.   Your thoughts are MOST appreciated.

[Cleveland Clinic]

Dear Cassandra309, We cannot comment specifically and make recommendations about an individual's case.  You may want to seek a consultation with a medical oncologist who specializes in breast cancer who can provide their input and recommendations for in context of the risks and benefits for your individual situation.