[escapee]

Acidic conditions means less oxygen, low pH is also low oxygen.

The lack of cellular oxygen appears to be the cause of lactic acid ( which is responsible for the lower PH of the patient with advanced stage cancer ) build up and the poor prognosis of the disease . Of course the lactic acid could probably make matter worse as per your opinion but it isn't the primary cause in the first place. Otherwise, all of the pro athletes are at risk of contracting cancer due to frequent generation of lactic acid .

Hypoxia inducible factor-1{alpha} as a cancer drug target -- Powis and Kirkpatrick 3 (5): 647 -- Molecular Cancer Therapeutics

Mammalian cells have an array of responses that maintain oxygen homeostasis; a balance between the requirement for oxygen as an energy substrate and the inherent risk of oxidative damage to cellular macromolecules. The molecular basis for a variety of cellular and systemic mechanisms of oxygen homeostasis are now being identified and the mechanisms have been found to occur at every regulatory level, including gene transcription, protein translation, posttranslational modification, and cellular localization (1).

Hypoxic cancer cells occur for a number of reasons. Oxygen is only able to diffuse 100–180 µm from a capillary to cells before it is completely metabolized. Therefore, any cell located greater than this distance from a blood vessel will be hypoxic. Hypoxia may occur when aberrant blood vessels are shutdown by becoming compressed or obstructed by growth, a feature commonly observed during the rapid growth of tumors.

Cells that become hypoxic convert to a glycolytic metabolism, become resistant to apoptosis (programmed cell death), and are more likely to migrate to less hypoxic areas of the body (metastasis). Hypoxic cells also produce pro-angiogenic factors, such as vascular endothelial growth factor (VEGF), which stimulate new blood vessel formation from existing vasculature, increasing tumor oxygenation and, ultimately, tumor growth. For this reason, hypoxic tumors are the most pro-angiogenic and aggressive of tumors.