Pancreatic Cancer Outcome: Local Treatment with Radiation Using MRI-Linac

PURPOSE/OBJECTIVE(S)

Stereotactic MR-guided on-table adaptive radiotherapy (SMART) is a surging modality in radiotherapy, delivering high dose radiation to the tumor in great proximity to susceptible organs. The aim of this study is to evaluate the clinical outcome in locally advanced or recurrent pancreatic tumors with or without prior irradiation.

MATERIALS/METHODS

All consecutive patients were treated in our center for pancreatic cancer (PC) using SMART technology to a prescription of 50Gy (BED10 100 Gy1o) in 5 fractions, with daily on-table adaptation of treatment plan. Endpoints for this retrospective, single center, IRB approved study were local control, overall survival, local disease-free period, acute and late toxicities.

RESULTS

Fifty-four PC patients were treated between 8.2019-9.2022, with median follow-up of 8.9 months from SMART (0.8-34 months). Forty patients had upfront inoperable PC (45% were metastatic at RT, five treated to liver metastatic lesions concomitantly) and fourteen patients had local recurrence following prior pancreatectomy, six of them had prior adjuvant RT. 87% received at least one round of chemotherapy (Oxaliplatin based- 72%), 25% received ≥2 regimens. Mean age was 68.9 (45-86) years. There was no significant difference in baseline parameters between prior pancreatectomy and inoperable groups. On-table adaptive replanning was performed for 100% of all (269) fractions (one patient received 4 fractions). No patient reported grade ≥2 acute GI toxicity. Six patients reported fatigue at the end of RT, four of them had prior radiation. Forty-eight patients were available for evaluation. Complete local control was achieved in 21.7% (10 patients) for median of 9 months (2.8-28.8 months), three had later local progression. Eight patients had regional or marginal recurrence following treatment. 6-months and 12-months OS was 75% and 52%, respectively. There was no significant difference in toxicity and outcome between post-pancreatectomy and inoperable groups.

CONCLUSION

Pancreatic cancer local ablative SMART is safe, with minimal treatment-related toxicity, even in previously irradiated patients. Local control with complete response was achieved by 20% of patients. Further studies are needed to evaluate long-term outcome and late toxicity.

A simplified scheme for generating narrow-band mid-ultraviolet laser radiation

We report on the development and characterization of continuous, narrow-band, and tunable laser systems that use direct second-harmonic generation from blue and green diode lasers with an output power level of up to 11.1 mW in the mid-ultraviolet. One of our laser systems was tuned to the mercury 6(1)S0 → 6(3)P1 intercombination line at 253.7 nm. We could perform Doppler-free saturation spectroscopy on this line and were able to lock our laser to the transition frequency on long time scales.