Partial Stereotactic Ablative Boost Radiotherapy for Bulky Lung Cancer.

To evaluate the efficacy of partial tumor stereotactic ablative boost radiotherapy (P-SABR) in the treatment of bulky (>8cm) lung cancer. Between January 2013 and October 2022, 57 patients with bulky (>8cm) lung cancer treated with P-SABR technique were analyzed. Thirty-seven (64.9%) of the patients had stage III, 16 (28.1%) had stage IV and 4 (7%) had postoperative recurrence or metastasis. Median tumor diameter treated by P-SABR was 10.01 cm (8.03–22.72 cm) and median tumor volume was 218.5 cm3 (82.40–2041.4 cm3). Twenty-five (43.9%) of the patients were treated with P-SABR alone and 19 (33.3%) were treated with P-SABR combined with conventional fractionation or SABR as definitive treatment. Thirteen (22.8%) patients received palliative treatment with P-SABR. P-SABR consisted of a SABR plan (6- 8 Gy per fraction in 3- 6 fractions) to the boost target volume (BTV) followed by one conventional plan to the planning target volume (PTV). BTV was the max volume within the tumor receiving SABR plan, in which the critical organ-at-risk (OAR) dose was reduced toto about 3 Gy/f. The median total dose of BTV was 76Gy (range: 65-110Gy) and PTV was 60Gy (range: 50-86Gy). With a median follow-up of 32 months (range, 1–75 months), 1-year, 2-year and 3-year overall survival rates were 36.2%, 26.1% and 23.2%, respectively. One-year, 2-year and 3-year local control rates were 81%, 70.8% and 70.8%, respectively. One patient (1.8%) had complete response (CR), 16 patients (28.1%) had partial response (PR), 7 patients (12.3%) had stable disease (SD) and 30 patients (52.6%) had progressive disease (PD). Of the 30 patients who had progressive disease, 25(83.3%) had local response but systemic progression, only 4 (13.3%) were presented with a RT-in-field- progression and 1 (3.3%) had both local recurrence and distant metastasis. For acute side effects, 2 (3.5%) patients developed grade III myelosuppression and 1 (1.8%) developed grade IV myelosuppression. One (1.8%) patient developed grade V radiation pneumonitis. No late severe toxicities (>CTCAE grade II) were reported. Partial stereotactic ablative boost radiotherapy could improve the local control rate of bulky lung tumors larger than 8cm and the toxicities were well tolerated. P-SABR might be a new choice for the treatment of bulky tumors. [ABSTRACT FROM AUTHOR]