Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma: Current Trends and Controversies

Geometrical tracking accuracy and appropriate PTV margins for robotic radiosurgery of liver lesions by SBRT

Purpose: To assess the geometrical accuracy and estimate adequate PTV margins for liver treatments using the Synchrony respiratory tracking system. Material and methods: Treatment log files are analyzed for 72 liver patients to assess tracking accuracy. The tracking error is calculated as the quadratic sum of the correlation, the predictor and the beam positioning errors. Treatment target rotations and rigid body errors reported by the system are also evaluated. The impact of uncorrected rotations is assessed by rotating the planned dose distribution and reassessing target coverage. Total PTV margins are estimated by summing in quadrature tracking errors and rigid body errors. Relationships are explored between tracking errors, model linearity and motion amplitudes of internal and external markers. Results: Margins of 3, 2, 2 mm in SUP-INF, LT-RT and ANT-POST directions, respectively, are sufficient to account for tracking and beam positioning errors for 95% of patients. If rigid body error is also considered, margins increase to 4 mm isotropic. Rotations could not be corrected for 92% of patients due to imperfect fiducial implantation and limitations in the magnitude of corrections that the system can apply. Uncorrected rotations would lead to average estimated dose reductions of 2.7% ± 5.8% of the prescribed dose for D99 of GTVs (5 mm PTV expansion) in which the target was well covered in the original plan (28 of 31 GTVs). 80% of tracking models exhibit near linear correlation between internal and external marker motions with small tracking errors (<2.2 mm). Conclusions: Isotropic PTV margins considering tracking errors and target rigid body errors could be used for liver SBRT treatments if rotational corrections can be calculated accurately so that systematic rotational offsets can be avoided. The linearity of the internal and external breathing motions might be useful for other types of treatment modalities for liver cancer.

Gross and microscopic changes of liver neoplasms and background hepatic structures following neoadjuvant therapy

Liver transplantation is a surgical option with curative intent used in the management of some cases of hepatocellular carcinoma and cholangiocarcinoma (hilar, rarely intrahepatic). A number of different therapeutic modalities including ablative techniques, arterially directed therapies, radiation and chemotherapy are used in the neoadjuvant setting prior to liver transplantation with the goals of preventing tumour progression, decreasing post-transplant recurrence and possibly downstaging patients with tumour burden beyond what is acceptable by current transplant criteria. Pathologists evaluating hepatic explants must be aware of these neoadjuvant therapies and the alterations induced by them in both tumourous and non-tumourous tissue. In this review, we discuss common neoadjuvant therapies used in in this setting, as well as the gross and microscopic changes induced by these presurgical treatments within hepatic neoplasms as well as the background hepatic parenchyma and nearby structures. Select secondary tumours involving the liver which are pretreated will also be discussed. Finally, proper reporting of these changes will be mentioned.

Combined stereotactic body radiotherapy and trans-arterial chemoembolization as initial treatment in BCLC stage B-C hepatocellular carcinoma

PURPOSE

We retrospectively evaluated the efficacy and safety of stereotactic body radiotherapy (SBRT) combined with trans-arterial chemoembolization (TACE) as initial therapy in Barcelona Clinic Liver Cancer (BCLC) system stage B-C hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Seventy-two patients received a single dose of TACE followed by SBRT 4 weeks later. All patients had tumor sizes ≥5 cm, at least 700 ml of disease-free liver, Child-Pugh (CP) score ≤ B7 and tumor nodules ≤5. SBRT dose, ranging from 6 × 5-8 Gy or 5-10 × 4 Gy, was individualized according to normal tissue constraints. No subsequent scheduled treatment was delivered unless disease progression was observed. Local control (LC), overall survival (OS), progression-free survival (PFS), response rate (RR), and toxicity were evaluated.

RESULTS

The patients' characteristics were: median age 60 years (range 28-87 years); CP score A/B (n = 68/4); BCLC stage B/C (n = 51/21); solitary/multifocal (n = 37/35); portal vein invasion (n = 18). The median tumor size and GTV were 11.2 cm (range 5.0-23.6 cm) and 751 cm³ (range 41-4009 cm³), respectively. The median equivalent dose in 2 Gy per fraction (EQD2, α/β = 10) was 37.3 Gy2 (range, 28-72 Gy2). The median follow-up time was 16.8 months (range, 3-96 months). The objective RR was 68% and the 1‑year LC rate was 93.6% (95% CI, 87.6-100%). The median OS was 19.8 months (95% CI, 11.6-30.6 months). SBRT-related grade 3 or higher adverse gastrointestinal events and treatment-related death occurred in three (2.8%) and one patient (1.4%) respectively. No patient developed classical radiation-induced liver injury.

CONCLUSION

Our experience suggests that combined TACE and SBRT can be a safe and effective initial therapy for BCLC stage B-C HCC with appropriate patient selection. Further prospective trials are warranted.