Tremendous progress has been made in cancer research over the years, and, as a result, immunotherapy has emerged as an important therapy for the treatment of cancer, either as a stand-alone treatment or in conjunction with other cancer therapies. Immunotherapy has demonstrated encouraging outcomes and offers a viable strategy for not only enhancing the quality of life but also dramatically boosting the overall survival rate of cancer patients. The objective of this systematic review was to assess the efficacy of immunotherapy in the treatment of cancer. Databases such as PubMed and Science Direct were searched from their inception until September 2021, using the following keywords: cancer immunotherapy, cancer recurrence, cancer treatment options, and cancer therapies. The systematic review was conducted in accordance with the PRISMA protocol. There were a total of 599 articles; however, after applying the inclusion and exclusion criteria, the final review ended up with 34 publications. In conclusion, the studies have demonstrated that immunotherapy is a viable alternative treatment option for patients with recurrent or metastatic cancer, since the overall survival rate and progression-free survival rate were shown to be successful.