Lattice Radiotherapy

Since 2014, when the first patient was treated, over 150 patients with bulky tumors worldwide have received Lattice Radio Therapy (LRT) using Particle therapy with heavy ions. This novel therapy, designed to target and reduce tumor size, has shown promising results with a response rate of >60% and with minimal toxicity. Patients suffering from large, inoperable tumors have found new hope through this innovative treatment. The procedure involves the localized delivery of various doses of radiation directly to the tumor, sparing the surrounding healthy tissue. This precision minimizes the side effects typically associated with conventional radiation therapy.

LRT can deliver high doses of radiation to various tumor areas without toxic effects on adjacent critical organs at risk. Introduced in 2010, LRT is based on 3-dimensional plans derived from GRID radiation therapy. Previously, GRID radiation delivered high doses to deep-seated tumors, often causing skin toxicity and difficulties in dose distribution within the tumor volume.

Large tumors require higher doses due to their dimensions and are often heterogeneous, with necrotic and hypoxic areas. Technological advances in LRT and the 3-dimensional view allow bulky tumors to be characterized into vertices (high-dose areas) and valleys (lower dose areas). Doses are calculated using this valley-to-peak ratio to create a heterogeneous dosimetry. Simulations have shown that hot spot diameters of 1 to 1.25 cm, separated by 1.7 to 1.8 cm, optimize the therapeutic ratio and spare normal tissue.

It is hypothesized that the tumor response to LRT is due to the modulation of the tumor microenvironment and host immune system, leading to tumor cell death. This leads to apoptosis (programmed cell death) releasing cancer antigens and inflammatory cytokines, triggering an acute inflammatory response. There appears to be interacellular signaling within the irradiated volume. High doses of radiation cause endothelial apoptosis, altering tumor microvasculature.. However, irradiation above the threshold of ablative doses does not enhance antigen-specific immunotherapy. A biweekly moderate radiation regimen (6 Gy twice a week) combined with a DNA vaccine generates more potent antigen-specific immunologic responses and anti-tumor effects compared to local irradiation or immunotherapy alone, or other radiation fractions (3 Gy four times per week or 12 Gy once per week).

Currently, LRT is used for tumors >45cc or >5cm in size or recurrent cancers of the lung, pancreas, cervix, rectum, brain, retroperitoneal and extremity sarcomas, kidney, melanoma, and recurrent and metastatic tumors. Despite its advantages, LRT is still relatively new and not yet widely available. Access to this treatment can be limited by geographic and financial factors, and not all medical facilities are equipped to offer it. However, as awareness of LRT grows and more clinics adopt the technology, it is expected that more patients will be able to benefit from this breakthrough therapy. Careful planning and patient selection are crucial. Further studies are needed for its widespread use in clinical practice for managing large tumors.