DIAGNOSIS AND STAGING SCREENING 2 Because cancers are most curable with surgery or radiation before they have metastasized, early detection and treatment have obvious potential benefits. In addition, small tumors are more responsive to chemotherapy, as discussed previously. Early diagnosis is difficult for many cancers because they do not produce clinical signs or symptoms until they have become large or have metasta-sized. Cancer screening programs are designed to detect signs of cancer in people who have not yet developed symptoms from cancer. Lack of effective screening methods for some cancers and inaccessibility of some anatomic sites further complicate the pro-cess. Education of the public on the early warning signs of common cancers is extremely important for facilitating early detection. For some cancers, effective screening procedures do exist. The Papanic-olaou (Pap) smear test, for example, is an effective tool to detect cervical cancer in its early stages. Self-examination of the breasts in women and of the testicles in men may lead to early diagnosis of cancers in these organs. The American Cancer Society has published guidelines for routine screening examinations (Table 130-4).