Patterns of Local Regional Failure in Head and Neck Cancer Treated with IMRT
Presenter: Tran, BN
Presenter's Affiliation: Mallinckrodt Institute of Radiology, Radiation Oncology Center, Washington University Medical Center, St. Louis, MO
Type of Session: Scientific
Intensity modulated radiation therapy allows sparing of the parotid glands when treating head and neck cancer. However, the effect on local regional control remains unanswered.
Materials and Methods
118 head and neck cancer patients, were treated by IMRT technique either definitively or postopperatively. 21 patients who received either palliative re-irradiation or IMRT as boost only were excluded from this analysis.
40 patients (46%) received definitive IMRT; 14/40 were treated with RT alone while 26 also received concurrent cisplatin based chemotherapy.
Median follow-up was 27 months (range, 14 to 48 months).
Definition: CTV1 (clinical tumor volume 1) included gross disease in definitive pt and surgical bed and lymph nodes w extracapsular extension in post-op pt. CTV2 included areas at risk but without apparent gross tumor on radiologic or pathologic review.
Lower neck was treated w AP port.
Doses were 70Gy to CTV1 and 60 Gy to CTV2 for definitive pts and 65 Gy/58 Gy for post-op pts.
Recurrent/persistent disease was defined on CT or MRI scans or surgical/pathologic findings at the time of surgery for salvage.
Treatment failures are defined as 1) "in-field," if >95% of disease "volume" (Vf) was within either CTV1 or 2, 2) "marginal," if 20-95% of Vf was within CTV1 or CTV 2 or 3) "outside" if < 20% of Vf was within either CTV1 or CTV2
11 pts had local-regional failure. 7/11 (64%) were inside CTV1, 1/11 failed marginal to CTV1 but inside CTV2. 1/11 failed outside CTV1 but inside CTV2. 2/11 failed in low neck.
DVH analysis of those failed within the IMRT field revealed that the recurrent/persistent disease received comparable or superior dose coverage relative to the CTV.
No marginal failure in the region adjacent to the spared parotid glands was seen in this study; therefore target definition and coverage was adequate in this study.
Strategies to escalate XRT dose and combine chemotherapy are needed in patients with radioresistent tumors that have a higher propensity to fail within the CTV1
Sparing of normal tissue with IMRT may allow dose escalation and possibly improve local regional control. Larger studies are needed to describe the failure patterns after IMRT treatment.
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