What aspect of treatment planning is directly affected by tumor depth?

The choice of light delivery method is directly affected by tumor depth because the effectiveness of photodynamic therapy (PDT) is significantly influenced by how deeply light can penetrate tissue. Different light delivery methods, such as interstitial light delivery, broad-field illumination, or fiber-optic systems, have varying capacities to reach tumors located at different depths.

For superficial tumors, external light can generally penetrate adequately and induce the desired photodynamic reaction. However, as tumor depth increases, external light becomes less effective; thus, alternative methods that can ensure adequate light delivery to deeper situated tumors are necessary. Using techniques like interstitial phototherapy, where light is delivered through fibers directly into the tissue, becomes crucial when targeting these deeper tumors to ensure that the photosensitizer is activated properly throughout the tumor mass.

In contrast, the selection of the photosensitizer, the patient's consent process, and the type of pain management, while important components of the overall treatment planning, are not as directly impacted by the tumor's depth in a manner requiring alteration of the methods used to deliver therapeutic light.